Rabies

I. Organism Information

A. Taxonomy Information
  1. Species:
    1. Rabies virus :
      1. Ontology: UMLS:C0034497
      2. GenBank Taxonomy No.: 11292
      3. Description: Rabies viruses belong to the Rhabdoviridae family, a constituent of the order Mononegavirales in which the viruses are characterized by a non-segmented negative-sense genome. The family is divided into two serologically distinct genera, Vesiculovirus and Lyssavirus. The Vesiculovirus genus includes the viruses causing vesicular stomatitis and antigenically related viruses and the Lyssavirus genus includes rabies, the rabies-related viruses, and many others which share only a distant relationship to rabies (King, 1998). The Lyssavirus genus includes seven genotypes: rabies virus (RABV, genotype 1), Lagos bat virus (genotype 2), Mokola virus (genotype 3), Duvenhage virus (genotype 4), European bat lyssavirus 1 (EBLV-1, genotype 5), European bat lyssavirus 2 (EBLV-2, genotype 6), and Australian bat lyssavirus (ABLV, genotype 7) (Arai et al., 2003). In addition to the rabies virus (RABV, genotype 1), Mokola virus (genotype 3), Duvenhage virus (genotype 4) , European bat lyssavirus 1 (genotype 5), European bat lyssavirus 2 (genotype 6), and Australian bat lyssavirus (genotype 7) have been associated with cases of human rabies (Jackson, 2002). Within each genotype, sublineages correspond to variants circulating in specific geographical regions and/or animal hosts. The genotypes further segregate in two phylogroups including genotypes 1, 4, 5, 6 and 7 (phylogroup I); and 2 and 3 (phylogroup II). Viruses of each phylogroup differ in their biological properties (pathogenicity, induction of apoptosis, cell receptor recognition, etc.). This classification will evolve, particularly as surveillance for bat lyssaviruses is reinforced. Four recent isolates of bat lyssavirus in Central Asia (Aravan virus (ARAV), Khujand virus (KHUV), East Siberia (Irkut virus (IRKV) and the Caucasian region (West Caucasian bat virus (WCBV) need to be characterized as new genotypes (WHO, 2002). Genotypes 2 - 4 have a wide geographical distribution in Africa, while genotypes 5 and 6 have a western and eastern Europe distribution, respectively (Heaton et al., 1999).
      4. Variant(s):
        • Rabies virus (strain AVO1) :
          • GenBank Taxonomy No.: 11293
          • Description: Strain AVO1 is the avirulent mutant of the CVS strain of rabies virus carrying a mutation in position 333 of the glycoprotein (Lafay et al., 1991).
        • Rabies virus (strain CVS-11) :
          • GenBank Taxonomy No.: 11294
          • Description: Challenge virus standard (CVS) is the mouse-brain strain of fixed rabies virus (WHO, 1973). CVS was first isolated in1882 from cow in France (Heaton et al., 1999). Highly neurovirulent strains such as the challenge virus standard (CVS) are highly neurotropic (Thoulouze et al., 1997).
        • Rabies virus (strain ERA) :
          • GenBank Taxonomy No.: 11295
          • Description: ERA strain of SAD virus (35-45 passages), porcine cell culture (WHO, 1973). Oral vaccination of foxes with the attenuated live virus Street Alabama Dufferin (SAD) strain of rabies virus which has been designated ERA, has been shown to be effective in the laboratory and has been used in field trials. Vaccination by the parenteral route with the ERA strain of rabies vaccine, produces a long duration of immunity, at least 4 years in cattle and 5 and 4 years, respectively, in dogs and cats. Foxes consuming a single bait containing the ERA strain of rabies virus were protected after 48 months against challenge with virulent virus (Lawson et al., 1997).
        • Rabies virus (strain HEP-FLURY) :
          • GenBank Taxonomy No.: 11296
          • Description: HEP Flury (227-230 passages) chick embryo-adapted rabies virus (WHO, 1973). Flury high egg passage (Flury-HEP) or Flury low egg passage (Flury-LEP) rabies virus strain used to produce two different types of purified chick embryo cell rabies vaccine (PCECV) (Moore et al., 2002).
        • Rabies virus (strain Nishigahara RCEH) :
          • GenBank Taxonomy No.: 11298
          • Description: The Nishigahara strain of rabies virus, a seed strain used for animal vaccine production in Japan, is believed to have been derived from the original Pasteur strain obtained from Paris in or before 1915. In Japan, the virus was serially passaged through several kinds of animals and cell cultures (Sakamoto et al., 1994). The virulent Nishigahara strain, kills adult mice after intracerebral inoculation (Takayama-Ito et al., 2006).
        • Rabies virus (strain Ontario fox) :
          • GenBank Taxonomy No.: 37132
          • Description: During the 1940s rabies in foxes spread into the Canadian provinces from the Artic regions and although in most of these regions it later died out, the disease has persisted in foxes in Ontario (King, 1998).
        • Rabies virus (strain ontario skunk) :
          • GenBank Taxonomy No.: 39005
          • Description: Although rabies outbreaks in most parts of the world tend to be host species-specific the rabies currently enzootic in the Canadian province of Ontario is hosted by two wildlife species, the red fox and the striped skunk (Nadin-Davis et al., 1993). Rabies in skunks spread from North Dakota into the prairie provinces during the late 1959s and 1960s (King, 1998).
        • Rabies virus (strain Pasteur / PV) :
          • GenBank Taxonomy No.: 103929
          • Description: Paris Pasteur strain of rabbit fixed rabies virus (WHO, 1973).
        • Rabies virus (strain PM) :
          • GenBank Taxonomy No.: 11297
          • Description: The PM (Pittman Moore) and Kissling rabies virus strains originated from the brain of a rabid cow in France in 1882. PM rabies virus strain used to produce human diploid cell rabies vaccine (HDCV), purified Vero cell rabies vaccine (PVRV) and purified duck embryo cell rabies vaccine (PDEV) (Moore et al., 2002). The Pitman-Moore (PM) strain is also designated as the PV-11 strain of Pasteur rabbit fixed rabies virus (WHO, 1973).
        • Rabies virus (strain SAD B19) :
          • GenBank Taxonomy No.: 11300
          • Description: The SAD strain (Street Alabama Dufferin) was originally isolated from a dog in Alabama, the USA, in 1935. Different variants, used for production of oral vaccines, were derived from that strain: SAD-Bern, SAD-B19, ERA, SAG, SAG2, Vnukovo-32 (Ondrejka et al., 2001).
        • Rabies virus (strain Street) :
          • GenBank Taxonomy No.: 31613
          • Description: When first isolated from natural human or animal hosts, rabies virus preserves its natural properties and is referred to as street virus. After adaptation to experimental animals by prolonged serial intracranial passage, a virus strain with altered properties is produced, and is referred to as fixed virus (Cohen, 1969). Most of the street virus isolates generally cause a lethal CNS infection (Tsiang, 1988).
        • Rabies virus (strain vnukovo-32) :
          • GenBank Taxonomy No.: 45418
          • Description: The vnukovo-32 strain of SAD virus (90-100 passages at 32 C), in primary hamster kidney-cell cultures, for live and killed-virus vaccine (WHO, 1973). The SAD strain (Street Alabama Dufferin) was originally isolated from a dog in Alabama, the USA, in 1935. Different variants, used for production of oral vaccines, were derived from that strain: SAD-Bern, SAD-B19, ERA, SAG, SAG2, Vnukovo-32. The Vnukovo-32/107 vaccination strain has been used to produce oral rabies vaccine Kamark for immunization of free living carnivores (Ondrejka et al., 2001).
        • Rabies virus Eth2003 :
          • GenBank Taxonomy No.: 265000
          • Description: Rabies virus Eth2003 was identified as the causative agent in the outbreak of rabies in the world's rarest canid, the endangered Ethiopian wolf (Canis simensis) in the Bale Mountains, Ethiopia, in 2003 and 2004 (Randall et al., 2004).
        • Thailand genotype 1 dog lyssavirus :
          • GenBank Taxonomy No.: 274042
          • Description: Rabies virus isolated in two dog-faced fruit bats (Cyanopterus brachyotis) in Thailand (Smith et al., 1967).
        • Rabies virus (strain RC-HL) :
          • GenBank Taxonomy No.: 11292
          • Description: RC-HL is an attenuated strain of Nishigahara strain of the rabies virus. It is used for the production of animal vaccine in Japan (Ito et al., 2001). The RC-HL strain was established from the Nishigahara strain, which had been maintained by rabbit brain passages, after 294 passages in chicken embryos, 8 passages in chicken embryo fibroblast cells, 5 passages in Vero cells, and 23 passages in hamster lung cells (Ito et al., 2001).
        • Rabies virus serotype 1 :
          • GenBank Taxonomy No.: 11292
          • Description: Rabies virus serotype 1, genotype 1, of the genus Lyssavirus, is an assembly of virus variants or genetic lineages each closely allied to a single speies of mammal. These rabies variants can be defferentiated by their antigenic makeup, as well as by characteristic patterns of nucleotide substitution in their RNA genome. This molecular variation has permitted identification of primary reservoir hosts for virus variants, detailed descriptions of the geographic destribution of variants, and identification of virus spillover into animals and humans (Childs, 2002).
        • Rabies virus strain SHBRV-18 :
          • GenBank Taxonomy No.: 11292
          • Description: Rabies virus SHBRV-18 is a highly neurotropic strain (Dietschold et al., 2005). The silver-haired bat variant of rabies virus (SHBRV) has been identified as the etiological agent of a number of recent human rabies cases in the United States without a history of conventional exposure (Morimoto et al., 1996).
        • Rabies virus strain SRV9 :
          • GenBank Taxonomy No.: 11292
          • Description: Oral vaccine candidate of Rabies virus, strain SRV9 is an intermediate plaque subclone of SAD B19 and has been used in the field with good safety and immunogenicity (Yuan et al., 2003).
        • Rabies virus strain:Ni-CE :
          • GenBank Taxonomy No.: 11292
          • Description: The attenuated Ni-CE strain causes nonlethal infection in adult mice after intracerebral inoculation (NCBI Entrez).
        • Rabies virus strain Flury-LEP :
          • Description: The Flury-LEP strain originated from a human patient in the USA who died of rabies in 1939 (Moore et al., 2002). LEP Flury (40-50 passages) chick embryo-adapted rabies virus (WHO, 1973).
        • Kissling rabies virus strain :
          • Description: The PM and Kissling rabies virus strains originated from the brain of a rabid cow in France in 1882. Kissling rabies virus strain of Challenge Virus Standard (CVS) is used to produce rabies vaccine adsorbed (RVA) (Moore et al., 2002).
    2. Lagos bat virus :
      1. Ontology: UMLS:C0318815
      2. GenBank Taxonomy No.: 38766
      3. Description: Lagos bat virus was isolated from frugivorous bats (Eidolon helvum) in Nigeria in 1956 and in 1974 from another bat (Micropterus pusillus) in the Central Africa Republic (Arai et al., 2003). It was later isolated from other bat species in Senegal and South Africa (WHO, 2002).
    3. Mokola lyssavirus :
      1. Ontology: UMLS:C0238283
      2. GenBank Taxonomy No.: 12538
      3. Description: Mokola virus was first isolated from shrews (Crocidura sp.) and a child in Nigeria in 1968, a girl in Nigeria in 1971, and cats in Zimbabwe (Arai et al., 2003). Since then isolations of this virus have been reported from shrews in Nigeria and Cameroon, humans in Nigeria, domestic cats in Zimbabwe, Ethiopia and South Africa, a domestic dog from Zimbabwe and a rodent, Lophuromys sikapusi, from the Central African Republic (Nel et al., 2000). Mokola virus is among the most genetically distant from rabies virus (genotype 1), and modern anti-rabies vaccines fail to protect against Mokola virus infection. Mokola virus has been responsible for a few cases of human and animal encephalomyelitis, largely dispersed throughout sub-saharian Africa (Le Mercier et al., 1997).
    4. Duvenhage virus :
      1. Ontology: UMLS:C0318813
      2. GenBank Taxonomy No.: 38767
      3. Description: Duvenhage virus was originally isolated from a human who died after being bitten by a bat in South Africa in 1970 and from Miniopterus sp. bats in 1981 (Arai et al., 2003).
    5. European bat Lyssavirus 1 :
      1. Ontology: UMLS:C1020183
      2. GenBank Taxonomy No.: 57482
      3. Description: EBLV-1 was isolated from bats (Eptesicus serotinus) in Germany in 1968, in Poland in 1985, in Denmark, Holland, and Spain in 1987, and in France in 1989. Some isolates of EBLV-1 were obtained from bats in Ukraine and from one human case of bat origin in Russia in 1985 (Arai et al., 2003). In 1985, an 11-year-old from Belgorod, Russia, was bitten on the lower lip by an unidentified bat and died with signs of rabies. The virus isolate was called Yuli virus and classified as European bat Lyssaviruses type 1 (genotype 5) (Jackson, 2002).
    6. European bat Lyssavirus 2 :
      1. Ontology: UMLS:C1020184
      2. GenBank Taxonomy No.: 57483
      3. Description: EBLV-2 was isolated from a human in Finland in 1985, and from bats in Holland, the Netherlands, Switzerland, and the United Kingdom. EBLV-2 is mainly carried by bats of the Myotis genus (Myotis dasycneme and M. daubentonii). ABLV was isolated from five species of flying fox bats, one species of an insectivorous bat, and two infected humans in 1996 (Arai et al., 2003).
    7. Australian bat Lyssavirus (ABLV) :
      1. Ontology: UMLS:C0949533
      2. GenBank Taxonomy No.: 90961
      3. Description: The Australian bat lyssavirus (ABLV) is a new lyssavirus closely related to classical rabies virus (Mackenzie, 2005). Rabies-related viruses in Australia have been identified as Australian bat lyssavirus (ABLV), found to date only in bats and following two fatal human cases. ABLV circulates as two variants, isolated respectively from flying foxes (Pteropus alecto) and an insectivorous bat species (Saccolaimus flaviventris), both assigned to genotype 7 (Lunt, 2006). Seemingly, these bat lyssaviruses are distributed throughout New South Wales, Queensland, Victoria and the Northern Territory, have been documented since at least 1995 (Niezgoda et al., 2002).
B. Lifecycle Information :
  1. Virion :
    1. Size: Approximately 100 to 430 nm long and 45 to 100 nm in diameter, when mature. Animal rhabdoviruses are usually less than 180 nm, but those isolated from plants may be longer (de Mattos et al., 2001).
    2. Shape: Rhabdoviruses are enveloped, rod-shaped particles. Typically, mature virions appear either as bullet-shaped particles with one rounded and one flattened end, or as bacilliform particles that appear hemispherical at both ends (de Mattos et al., 2001).
    3. Picture(s):
      1. Rabies virion: Basic structure and composition



        Description: Rabies virions are bullet-shaped with 10-nm spike-like glycoprotein peplomers covering the surface. The ribonucleoprotein is composed of RNA encased in nucleoprotein, phosphorylated or phosphoprotein (CDC(a)).
      2. Rabies virion: Cross-section



        Description: The cross-sectional diagram below demonstrates the concentric layers: envelope membrane bilayer, M protein, and tightly coiled encased genomic RNA (CDC(a)).
      3. Cycle of Infection and Replication



        Description: Cycle of Infection and Replication of the human rabies virus (copyright: CDC) (CDC(a)).
    4. Other:
      1. Stages of Replication The replication and assembly of members of the Rhabdoviridae family can be divided into distinct stages. Although many of these events occur simultaneously in an infected cell, it is convenient to consider the process of infection as a linear series of events that proceeds in the following order: adsorption, entry and uncoating, transcription, replication, assembly and binding (Rose and Whitt, 2001). Rhabdoviral infection is initiated by attachment of virus to a receptor on the host cell surface. The receptor for rabies virus has been controversial, and recent evidence indicates that several different receptors can be used After binding, the virions are endocytosed through a clathrin-depended pathway typical of receptor-mediated endocytosis. A membrane fusion reaction between the envelope of the endocytosed virion and the endosomal membrane catalyzed by the G protein results in the release of ribonucleoprotein (RNP) core into the host cell cytoplasm. Either concomitant with membrane fusion or immediately after, M protein dissociates from the RNP core. The combined processes of membrane fusion and M protein dissociation constitute the uncoating event for rhabdoviruses The first synthetic event that occurs after uncoating of RNPs is transcription of viral-specific mRNAs by the L-P3 polymerase complex brought into the cell by the virion. Primary transcription occurs in the absence of protein synthesis, unlike genome replication, which requires newly synthesized N and P proteins and ongoing translation During transcription, the polymerase responds to signals that result in the synthesis of the leader RNA and individual mRNAs. In contrast, during replication, the polymerase must ignore these signals and synthesize genome-length positive stranded RNA. This RNA is then replicated to form the genomic negative-stranded RNA. Encapsidation of the genome and antigenome by N protein is intimately tied to and essential for virus replication. Encapsidation occurs as the genomic RNA is synthesized rather than after the synthesis is complete. For rabies virus, leader encapsidation may also be regulated by the phosphorylation status of N protein The process of rhabdovirus assembly can be divided into three distinct phases: (a) encapsidation of newly replicated genomic RNA by N protein, (b) simultaneous condensation of the ribonucleocapsid core by M protein and association with the plasma membrane, and (c) particle development and release. The first step, encapsidation, occurs in the cytoplasm and results when nascent genomic RNA associates with newly synthesized N, P, and L proteins to form RNP complexes. These are often referred to as nucleocapsids or RNP cores. After encapsidation, the RNP complex associates with the plasma membrane and condense into a tightly coiled structure called a skeleton before release from the cell. Numerous studies have demonstrated that the matrix protein is responsible for both of these events. After RNP condensation, rhabdovirus particles are released from infected cells by budding from the cell surface. During budding, the condensed core becomes enclosed within a membrane envelope that, have molecules of virally encoded G protein and smaller amounts of normal cellular membrane proteins. G protein, however, is not needed for rabies budding, although it greatly enhances budding efficiency. The assembly of glycoproteins into rabies appears highly dependent on the rabies G cytoplasmic tail, although infectious rabies virus can be recovered when the entire cytoplasmic domain is deleted. The final step in virus budding requires a membrane fission event that results in release of the virus from the host cell. Little is know about how this occurs, but it has been suggested that the PPxY motif in M protein facilitates virus release through the recruitment of host factors that contain WW domains (Rose and Whitt, 2001).
C. Genome Summary:
  1. Genome of Rabies virus
    1. Description: Rabies virus, complete genome (NCBI Entrez)
    2. Chromosome:
      1. GenBank Accession Number: NC_001542
      2. Size: 11932 bp ss-RNA (NCBI Entrez)
      3. Gene Count: 5 (NCBI Entrez)
      4. Description: The rabies virus has a single non-segmented negative strand RNA genome. The genetic information is present in the form of a helical ribonucleoprotein complex (RNP), in which the linear RNA is tightly associated with the viral nucleoprotein. The genome of RV and VSV comprises only five genes encoding viral proteins, namely nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and the viral RNA polymerase (L). The order of the genes, namely 3'-N-P-M-G-L-5', is highly conserved (Finke and Conzelmann, 2005). From the 3' to the 5' end the genomic RNA encodes a leader RNA of about 50 nucleotides, followed by the genes N,P, M, G, and L. Each gene is composed of an internal protein-coding region flanked by non-translated regions. Genes are also separated by non-transcribed intergenic regions.The latter are generally short (less than 5 nucleotides) and are bordered by the start and stop signals consisting of nine-nucleotide consensus sequences that govern gene transcription. Despite the considerable length (450 nucleotides) of the G-L intergenic region, it encodes no substantial polypeptide and thus has been proposed to correspond to a remnant gene (pseudogene) (King, 1998). The P protein is an essential co-factor of the L polymerase and is required for RNA encapsidation. Both P and L are associated with the helical RNP. During budding of the virus, such RNPs are enwrapped into an envelope containing an inner layer of M protein and the transmembrane spike proteins. The G spikes are required for virus entry into cells, by interacting with cell receptors and promoting virus and cell membrane fusion. They are also the major antigens stimulating production of virus-neutralizing and protective antibodies (Finke and Conzelmann, 2005).
      5. Picture(s):
        1. Rabies Genome



          Description: The rabies virus genome is single-stranded, antisense, nonsegmented, RNA of approximately 12 kb. There is a leader-sequence (LDR) of approximately 50 nucleotides, followed by N, P, M, G, and L genes (Copyright: CDC) (CDC(a)).

  2. Genome of Mokola lyssavirus
    1. Description: Mokola virus, complete genome (NCBI Entrez)
    2. Chromosome:
      1. GenBank Accession Number: NC_006429
      2. Size: 11940 bp ss-RNA
      3. Gene Count: 5 genes
      4. Description: The Mokola virus genome is the third lyssavirus genome to be completely sequenced. Its 11939 nucleotides (nt) are extensively used for coding purposes since 90.3% (10782 nt) code for the N, P, M, G and L proteins, and only 7.3% (941 nt) are neither protein nor known signal-coding sequences (Le Mercier et al., 1997). The nucleotides of the rabies related Mokola virus (MOKV) genome are less well conserved than the PV and SAD-B19 rabies virus genomes in many regions throughout the genome, particularly in the noncoding regions and in the coding sequences of the P and G proteins (Wunner, 2002). We learn from the sequences of Pasteur Virus (PV) strain, Street Alabama Dufferin (SAD)-B19 strain, Australian bat Lyssavirus and the Mokola (MOKV) viral genomes that even for the most divergent rabies related lyssavirus (MOKV), the general organization of the genome is the same and that only slight differences are observed in the length of the genome and in the intergenic sequences between rabies and the rabies-related viruses. For example, the 3" half of the Mokola virus genome, which includes the first four nonoverlapping ORFs that code for the structural viral proteins (N, P, M, and G), is slightly longer than the PV and SAD-B19 genomes by 25 and 29 nucleotides, respectively. Both the second ORF (P gene) and the fourth ORF (G gene) of the Mokola virus genome encode proteins that are six amino acids longer and three amino acids shorter, respectively, than the corresponding ORFs in the rabies virus genome (Wunner, 2002).

  3. Genome of Australian bat Lyssavirus (ABLV)
    1. Description: Australian bat lyssavirus, complete genome (NCBI Taxonomy)
    2. Chromosome:
      1. GenBank Accession Number: NC_003243
      2. Size: 11,822 bp ss-RNA
      3. Gene Count: 5 genes
      4. Description: The nucleocapsid protein (N), matrix protein (M), phosphoprotein (P), glycoprotein (G) and polymerase (L) genes of the Australian bat lyssavirus (ABL) insectivorous isolate were compared with that previously described from a frugivorous bat (Pteropus sp.), and showed sequence divergence at both the nucleotide and amino acid sequence level of 20% and 4-12%, respectively. Comparison of deduced protein sequences of ABL isolates from Pteropus and insectivorous bats, showed that viral isolates were homologous and varied by only a few percent. However, these viruses separated into two distinct clades; those isolated from Pteropus or those from Saccolaimus flaviventris bats, when comparisons were made at the nucleotide level. Nucleoprotein sequence comparisons also showed insectivorous isolates to be of the same putative genotype (genotype 7) as that isolated from frugivorous bats (Gould et al., 2002).

II. Epidemiology Information

Rabies is an enzootic disease widespread throughout the world and is a serious problem in developing countries. Human infections and deaths are an unfortunate consequence of biologic processes of virus maintenance in which humans play no significant role. Rabies virus and the other six recognized members of the Lyssavirus genus, some of which cause diseases indistinguishable from rabies in humans, are adapted to various animals species on which they depend for their existence (Childs, 2002). Rabies is still present in Europe in 2005. Its incidence in humans remains limited (fewer than 5 human cases per year) through the application of strict prophylactic measures (anti-rabies treatment) and by means of veterinary rabies control measures in the domesticated and wild animal populations. The main indigenous animal reservoirs are: the dog in eastern European countries and on the borders with the Middle East; the fox in central and eastern Europe; the racoon dog in northeastern Europe; and the insectivorous bat throughout the entire territory (Bourhy et al., 2005). Rabies viruses have been reported in Kazakhstan, central Asia. Field rabies viruses have been isolated and characterized in Asia, specifically Pakistan, China, Indonesia, Thailand, the Philippines, Malaysia, India, and Sri Lanka. Isolation of lyssaviruses from bats has been reported only in India and Thailand; however, these viruses were reported as RABV. Recently, Arguin et al. detected neutralizing antibodies against ABLV in the serum of six bat species (Mineopterus schreibersi, Taphozous melanopogan, Philetor brachypteus, Scotophilus kuhli, Pteropus hypomelanus, and Rousettus amplexicaudatus) in the Philippines (Arai et al., 2003). The wolf still plays an important role as vector along with the dog in some regions of Iraq, Iran, Afghanistan and some republlics of the Soviet Union. In recent decades the raccoon dog, transported westwards from Siberia for fur and hunting purposes, has become a prolific vector of the disease in the western Soviet Union and Poland. The rabies type currently prevalent in Africa is canine, but in southern Africa sylvatic rabies independent of the canine cycle is found in the yellow mongoose and in the herbivorous kudu antelope. Antelope rabies became established in Namibia in 1977 and claimed the lives of 50,000 antelope annually until 1983, since when the epidemic has spontaneously regressed (Gardner and King, 1991). In central and South America, canine rabies is the cuase of many human deaths and vampire bats rabies is responsible for severe economic losses in cattle. In North America, 40 years of vaccination and pet animal control has greatly reduced canine rabies, but the disease is enzootic in foxes, skunks and raccoons. Within these species, compartmentation occurs; that is, the disease is reported in one major host species in certain geographical areas while it is reported much less frequently in the same species in other areas of endemic rabies. Rabies in insectovorous bats account for some 15% of all rabies cases in the USA ans Smith and Baer have also shown that spillover of disease from bats to terrestrial animals occurs rather more frequently than was at one time thought, although there is no suggestion that at present these bat rabies viruses cause cycles of disease in terrestrial animals (Gardner and King, 1991). Despite its relative rarity in industrialized countries, rabies continues to cause significant mortality worldwide with annual deaths estimated at over a hundred thousand. Recent epizootics in wild animals in the United States have renewed fears of rabies in this country (Wilkerson, 2000). Thirty-eight cases of human rabies occurred in the United States and its territories from 1960 to 1979. The major source of exposure to rabies has changed from indigenous dogs and cats in the 1940s and 1950s to wild carnivores and bats (11 of the 27 cases with known exposures); unusual exposures (3 cases) and exposures in a foreign country (7 cases) have also become more important. No exposure could be identified for 6 of the 38 cases (Anderson et al., 1984).

A. Outbreak Locations:
  1. Zimbabwe, Africa: During an outbreak of rabies in Zimbabwe from 1980 to 1983, the majority of the documented animal cases occured in jackals (74.3% of 404 cases; Canis mesomelus and C. adustus), but dogs were the most serious threat to humans (Childs, 2002).
  2. Canada: The first case of raccoon strain rabies in New Brunswick, reported on 12 September 2000, was retrieved from the town of Heathland in Charlotte county which lies on the US border with Maine. Between the autumn of 2000 and May 2002 many additional cases were reported from this same area; the epizootic appeared to be confined to St Stephen, the major town of the area which is in close proximity to a bridge connecting Canada with the United States, and neighbouring communities within 20 km radius of St Stephen (Nadin-Davis et al., 2006).
  3. Flores, Indonesia: Flores is an isolated previously rabies-free Indonesian island which has been experiencing a canine rabies outbreak which resulted in at least 113 human deaths. It started with the importation of three dogs from rabies endemic Sulawesi in September of 1997. Local authorities responded with massive killing of dogs starting in early 1998. Approximately 70% of the dogs, in the district where rabies had been introduced, were killed during that year, yet canine rabies still exists on Flores at this time (June 2004) (Windiyaningsih et al., 2004).
  4. Finland: Between 1988 and 1989, wildlife rabies re-appeared in Finland after 29 years of freedom from the disease. The only exception to this was a single case of human rabies which was considered to be of bat origin and was subsequently shown to be caused by European bat lyssavirus type 2 (EBLV-2). The first cases of the outbreak were recorded in April 1988 in the province of Kymi on the coast by the Gulf of Finland. Rabies was diagnosed in a dog (Canis familiaris) and a red fox (Vulpes vulpes). However, as the epizootic developed, the principal species involved was the raccoon dog (Nyctereutes procyonoides), a species introduced into the country in the 1930s (John and Fooks, 2005).
  5. Las Cruces, New Mexico: Between May 1967 and February 1968 an unusual outbreak of rabies was observed in the wild carnivore colony at the Public Health Service's Southwest Rabies Investigation Station in Las Cruces, New Mexico. Sixty-four animals died of rabies, including 39 which had no known exposure history. Investigation confirmed that direct contact transmission did not occur and suggested that airborne dissemination of virus may have been responsible for the outbreak. Probable predisposing factors included experimentation with aerosol rabies transmission and extensive use of bat rabies isolates from which a strain may have been selected which was well adapted for non-bite transmission (Winkler et al., 1972).
B. Transmission Information:
  1. From: Animal To: Animal/Human
    Mechanism: The most common mode of rabies virus transmission is through the bite and virus-containing saliva of an infected host (CDC(c)). Rabies cases are almost attributable to the bite of a rabid animal. For example, animal bites were the cause of 99.8% of 3,920 human rabies cases examined at various Pasteur Institutes between 1927 and 1946 (de Mattos et al., 2001).

  2. From: Animal To: Human
    Mechanism: Aerosol transmission of rabies can occur under some field conditions, but these involve unusual circumstances. Aerosol infection has been suggested as a result of laboratory accidents, in an unusual cave setting involving millions of Mexican free-tailed bats, and in experimental studies with a unique bat rabies virus variant (Niezgoda et al., 2002). Viral entry by the olfactory and oral routes is much less common than by bites. Relatively little experimental work has been done with routes of viral entry other than one stimulating a bite exposure (using inoculation techniques). The nasal mucosa has been shown to act as a site of viral entry by suckling guinea pigs that have inhaled street rabies virus (Jackson, 2002).

  3. From: Animal To: Animal/Human
    Mechanism: Oral exposure may result in infection, albeit with relatively low efficiency (Niezgoda et al., 2002). Handling and skinning of infected carcasses and perhaps consumption of raw infected meat have resulted in transmission of rabies (Jackson, 2002). Consumption of infected carcasses by carnivores may be the most relevant example of this scenario. For example, transmission could be enhanced through penetration of the oral or esophageal mucosa by bone fragments contaminated with highly infectious material, such as brain and salivary gland tissue. The mechanism has been hypothesized to contribute to the maintenance of artic fox rabies, where contact between potential hosts is minimal but where transmission may be facilitated due to the preservation of virus in carcasses under polar conditions. Infectious virus may be recovered months later in a frozen fox carcass during winter but could be inactivated within hours during the summer within the decomposing tissues of a road-killed raccoon in the Florida sun (Niezgoda et al., 2002).

  4. From: Human To: Human
    Mechanism: Human-to-human transmission of the rabies virus occurred in at least 8 patients worldwide who received corneal transplants from individuals who died from rabies that was undiagnosed at the time of transplant ( AHFS, 2005b). In July 2004, the Centers for Disease Control and Prevention (CDC) reported on a rabies-virus infections in four transplant patients in the USA. These patients received various organs (lung, liver, kidney) from the same donor who was not diagnosed with rabies before death. However, post-mortem diagnosis of rabies infection of the donor and of the four organ recipients was later confirmed at CDC (Dietzschold and Koprowski, 2004). Contamination of other mucous membranes, such as eyes and nose, is considered a potential exposure to rabies. However, this is largely based on human infection following corneal transplantation (Niezgoda et al., 2002). Most other reported cases of human-to-human transmission have not been well documented. Two patients with rabies from Ethiopia were described, and their only known exposure was contact with family members who died of rabies. In another incidence, A 41-year-old woman died of rabies 33 days after her 5-year-old son died of rabies; he had bitten his mother on her little finger. A 5-year-old boy presented with rabies 36 days after his mother died of rabies; he had repeatedly received kisses form his mother on his mouth during her illness. Sexual transmission of rabies is not well documented. Although natural human-to-human transmission of rabies likely occurs very rarely, anyone in direct contact with rabies patients, including family members and healthcare workers, should employ strict isolation precautions in order to minimize the risk of transmission of the virus via saliva or other secretions. Evidence of transplancental transmission of rabies virus exists from a single report from Turkey (Jackson, 2002). In the US, stringent guidelines for acceptance of donor corneas have been implemented to reduce this risk. Transmission of rabies virus from the bite of a human with rabies or a non-bite exposure to individuals infected with rabies is theoretically possible ( AHFS, 2005b).

C. Environmental Reservoir:
  1. Dog :
    1. Description: On a global basis, the domestic dog remains the most important reservoir of rabies in overall case numbers and with regard to transmission to humans. In regions where strict control of free-ranging dogs and mandatory perenteral rabies vaccination are enforced, canine rabies virus variants have been eliminated successfully. Examples of such areas include Great Britain, Japan, Canada, and the United States. Recently numerous countries in Latin America have made tremendous progressin the application of stray dog control and mass vaccination with consequent control of canine rabies and markedly reduced human rabies over large geographic areas. Although rabies has been eliminated in most European countries, canine rabies remains largely uncontrolled throughout most of Asia and Africa (Niezgoda et al., 2002). Dogs in Asia and Africa remain the main reservoir and transmitter of rabies to humans (Arai, 2005). In the Philippines, dogs (99%) are the main reservoirs of RABV, and this reflects the urban epidemiological cycle of rabies transmission, mainly from dog to dog with occasional spillover to man (Fooks et al., 2003).
    2. Survival Information: The incubation period of rabies in dogs may be as short as 10 days or as long as several months (Niezgoda et al., 2002).
  2. Fox :
    1. Description: Predominant wild reservoirs belong to the family Carnivora and include foxes in the Artic (Alopex lagopus), Canada, central and western Europe (Vulpes vulpes), and scattered foci elsewhere throughout North America (e.g., Urocyon cinereoargenteus) (de Mattos et al., 2001). Foxes in the Middle East form a wildlife reservoir (King, 1998). With its occurrence in Eurasia, North America, and northern Africa and introduction to Australia, the red fox (Vulpes vulpes) is one of the most widely distributed and abundant wild carnivores in the world. Perhaps more is known about rabies in this fox than any other wild mammal, not only related to its significance as a mojor reservoir but also due to the influence of directed research during the past 30 years, coordinated by the World Health Organization (WHO) (Niezgoda et al., 2002).
    2. Survival Information:
  3. Raccoon :
    1. Description: The common racoon (Procyon lotor) is widely distributed from Canada through Central America and was introduced into Russia and Western Europe as well as onto a number of islands, including Japan. Over the past 50 years, racoons have become recognized as a significant host of wildlife rabies in North America. Despite its relevance as a reservoir, rabies pathogenesis in raccons is neither well understood nor well described experimentally. Most published responses of racoons to rabies virus infection have been conductednusing a number of other isolates, including a fox, a bat, a skunk, and a dog (Niezgoda et al., 2002).
    2. Survival Information:
  4. Skunk :
    1. Description: Today in North America, reports of rabies in skunks occur mainly in four geographic regions: (1) the eastern United States, (2) the north central United States and the Canadian provinces of Manitoba, Saskatchewan, and Alberta, (3) California, and (4) the south central United States and Mexico. Rabies in these areas (in skunks and, to a large extent, in other terrestrial mammals) is caused mailnly by four different street virus variants. In the eastern United States, cases are primarily related to spillover from infected racoons, whereas in the other three, the viruses are adapted to skunks as the primary reservoir (Niezgoda et al., 2002).
    2. Survival Information:
  5. Coyote :
    1. Description: There are other important reservoirs, including coyotes in Asia, Africa and North America (Fu, 1997).
    2. Survival Information:
  6. Bat :
    1. Description: Recently, bat rabies has emerged as an important epidemiologic reservoir in some parts of the world (i.e. the Americas and Australia). In North America, most documented human rabies deaths occurred as a result of infection from the silver haired bat rabies virus variant and in Australia at least two human deaths have occurred from exposure to a previously unrecognized rabies virus. In South America, wildlife rabies, especially bat rabies is increasing. For the first time in 2003, more people died from rabies following bites from wildlife than from dogs in South America (WHO Fact Sheet N 99, September 2005). It has been known for many years that the vampire bat species Desmodus rotundus is a rabies reservoir and frequently transmits the disease to terrestrial animals, especially livestock species, upon feeding. Vampire bat populations appear to be on the increase in many parts of Latin America, probably as a direct consequence of human settlement and agricultural practices in areas of suitable vampire bat habitat, with inevitable significant increases in the economic and public health impacts of vampire bat rabies. In Mexico, human rabies cases due to bat reservoirs now comprise a significant proportion of all cases; it was reported that of four human deaths in 2000 two were due to unidentified bats and in 2002 all three Mexican cases were associated with bat contact (Nadin-Davis and Loza-Rubio, 2006). Prior to May 1996, Australia had been considered free of rabies and rabies-like viruses. This status was challenged, however, when a virus with a high degree of antigenic and genetic similarity to rabies virus (RV), subsequently named Australian bat lyssavirus (ABL), was isolated from a juvenile black flying fox. Since that time, all four common species of Australian flying fox (Pteropus alecto, P. poliocephalus, P. scapulatus and P. conspicullatus) and an insectivorous bat species, Saccolaimus flaviventris (the yellow-bellied sheath-tailed bat), have been found to be reservoirs of ABL in Australia (Guyatt et al., 2003). In the Americas, the bat species Desmodus rotundus (vampire bat), Tadarida brasiliensis (Brazilian free-tailed bat), Eptesicus fuscus (big brown bat), Lasiurus species (L. borealiz, L. cinereus), Lasionycteris noctivagans (silver-haired bat), Pipistrellus subflavus (eastern pipistrelle) and Myotis species (M. lucifugus; M. yumanensis, M. californicus; M. evotis) have all been identified as rabies virus reservoirs that harbour distinct RV variants. These RV variants generally separate into phylogenetic divisions that represent the lifestyle of their chiropteran hosts, i.e. migratory versus non-migratory, colonial versus solitary, insectivorous versus haematophagus. While most of these variants co-segregate only with their specific host reservoirs making spillover events to terrestrial animals uncommon, some have been associated with infection of non-chiropteran species, especially humans and domestic animals (Guyatt et al., 2003).
    2. Survival Information:
  7. Jackal (Arai, 2005):
    1. Description: Since 1956, red foxes (Vulpes vulpes) and, to a lesser extent, golden jackals (Canis aureus), have been the primary vectors maintaining endemic wildlife rabies in Israel (Yakobson et al., 2006).
    2. Survival Information:
  8. Mongoose (Arai, 2005):
    1. Description: Important reservoirs include mongoose in Asia, Africa and the Caribbean islands (Fu, 1997).
    2. Survival Information:
  9. Wolve (Arai, 2005):
    1. Description: Dogs in Asia and Africa remain the main reservoir and transmitter of rabies to humans. The others are mainly coyotes, foxes, jackals, mongooses, raccoons, skunks, wolves and bats (Arai, 2005).
    2. Survival Information:
D. Intentional Releases:
  1. Intentional Release information :
    1. Description:
    2. Emergency contact: Prompt consultation with public health officials is advised, as this decision is based on the current incidence of rabies in the animal species involved in the exposure. The most recent report of the Immunization Practices Advisory Committee is also an important source of information. The CDC manages a 24-hour telephone system with rabies information (404-332-4555) (Bleck and Rupprecht, 2000).

III. Infected Hosts

  1. Homo sapiens:
    1. Taxonomy Information:
      1. Species:
        1. Human (NCBI Taxonomy):
          • Ontology: UMLS:C0020114
          • GenBank Taxonomy No.: 9606
          • Scientific Name: Homo sapiens (NCBI Taxonomy)
          • Description: Human infections and deaths are an unfortunate consequence of biologic processes of virus maintenance in which humans play no significant role. Rabies virus and the other six recognized members of the Lyssavirus genus, some of which cause diseases indistinguishable from rabies in humans, are adapted to various animals species on which they depend for their existence (Childs, 2002).

    2. Infection Process:
      1. Description: Following primary infection, the virus enters an eclipse phase in which it cannot be easily detected within the host. This phase may last for several days or months. Investigations have shown both direct entry of virus into peripheral nerves at the site of infection and indirect entry after viral replication in nonnervous tissue (i.e., muscle cells). During the eclipse phase, the host immune defenses may confer cell-mediated immunity against viral infection because rabies virus is a good antigen. The uptake of virus into peripheral nerves is important for progressive infection to occur. After uptake into peripheral nerves, rabies virus is transported to the central nervous system (CNS) via retrograde axoplasmic flow. Typically this occurs via sensory and motor nerves at the initial site of infection. The incubation period may vary from a few days to several years, but is typically 1 to 3 months. Dissemination of virus within the CNS is rapid, and includes early involvement of limbic system neurons. Active cerebral infection is followed by passive centrifugal spread of virus to peripheral nerves. The amplification of infection within the CNS occurs through cycles of viral replication and cell-to-cell transfer of progeny virus. Centrifugal spread of virus may lead to the invasion of highly innervated sites of various tissues, including the salivary glands. During this period of cerebral infection, the classic behavioral changes associated with rabies develop (CDC(c)).
        • Infectious path of rabies virus (CDC(a)):



          Description: The infectious path of rabies virus: (1): Raccoon is bitten by a rabid animal. (2): Rabies virus enters the raccoon through infected saliva. (3): Rabies virus spreads through the nerves to the spinal cord and brain. (4): The virus incubates in the raccoon's body for approximately 3-12 weeks. The raccoon has no signs of illness during this time. (5): When it reaches the brain, the virus multiplies rapidly, passes to the salivary glands, and the raccoon begins to show signs of disease. (6): The infected animal usually dies within 7 days of becoming sick (copyright: CDC)

    3. Disease Information:
      1. Rabies (i.e., Rabies) :
        1. Pathogenesis Mechanism: Bites by rabid animals generally inoculate virus-laden saliva through the skin into muscle and subcutaneous tissues. Other routes of infection are rare. During the incubation period the virus can replicate locally in muscle cells or attach directly to nerve endings. Having gained access to peripheral nerves, it travels in a retrograde direction within the axoplasm. When the virus reaches the central nervous system, there is massive replication on membranes within neurons. Direct transmission of virus occurs from cell to cell across synaptic junctions. At the onset of illness when evidence of neuronal dysfunction appears, there is little or no apparent histopathological change. Centrifugal spread of virus from the central nervous system in somatic and autonomic nerves deposits virus in many tissues, including skeletal and cardiac muscle, adrenal glands, kidney, retina, cornea, pancreas, and nerves around hair follicles. Productive viral replication with budding from plasma membranes takes place predominantly in the salivary glands, excreting virus that is transmissible to other mammals (Warrell and Warrell, 2004). The first clinical symptom is usually neuropathic pain at the wound site. This is caused by viral replication at the dorsal root ganglia and ganglionitis. Major clinical signs are related to the virus-induced encephalomyeloradiculitis. Two major clinical presentations are observed: furious and paralytic forms that cannot be correlated with any specific anatomical lacalization of rabies virus in the CNS. Nontheless, peripiheral nerve dysfunction is responsible for weakness in paralytic rabies. In furious rabies electrophysiological studies indicate that anterior horn cell dysfunction even in the absence of clinical weakness. Without intensive care, death occurs within a few days (1-5 days) of the development of neurological signs. Rabies is inevitably fatal (WHO, 2002). In human beings, the symptoms of encephalitis and even death can occur with only minor histopathological changes. Rabies virus must have some profound effects on the functions of infected and some uninfected neurons. Few abnormalities of organelle structure are seen on electron microscopy in neurons infected with street virus. Minor electroencephalographic changes during animal infection indicate neuronal dysfunction. Although MRI shows a range of abnormalities as the human encephalitis progresses, no consistent pattern has yet emerged. Abnormalities of neurotransmitter functions affecting serotonin, opioid, GABA, and muscarinic acetylcholine transmission have been found experimentally, in some cases in specific brain areas, and not always associated with the presence of virus. Results show no clear explanation of the limbic-system dysfunction suggested by the classic clinical features. Changes in neurotransmitter functions could lead to failure of brain networking and regulation of responses. The involvement of excitatory aminoacids in neuronal toxicity is a possibility. Many non-competitive antagonists of N-methyl-D-aspartate have an antiviral effect on viral replication. Surprisingly, one of these, ketamine, specifically inhibits transcription of the rabies virus genome. The effect of infection on the function of neuronal membrane ion channels could be reduction of normal inhibitory events. Apoptosis could contribute to pathogenesis since fatal infection of mice is associated with apoptosis of T cells invading the brain and neuronal preservation. By contrast, neuronal apoptosis occurs in non-lethal infection, with development of an immune response. The role of nitric oxide toxicity in neuronal dysfunction in rabies is not clear, but it could be related to the LC8 inhibition of neuronal nitric oxide synthase, through interaction with the viral phosphoprotein. Although rabies infection progressively decreases host gene expression overall, a few genes are upregulated, some associated with the interferon response, host-cell protein synthesis, synaptic vesicle function, and neuron growth and spread, even in some uninfected or nonneuronal cells. One hypothesis on the cause of death is therefore that short-circuiting of normal neural pathways results from the formation of new interneuronal connections. Another hypothesis is that disruption of neuronal metabolism ends in the exhaustion of metabolic pools (Warrell and Warrell, 2004).


        2. Incubation Period: The wide variability of the incubation period of rabies in man was noted in early literature. In modern times the incubation period in man, as defined by the interval between exposure and the first symptoms in the prodromal stage, is more variable than in any other acute infection. Fishbein has cited extremes from as short as 4 days to as long as 14 to 19 years, although in cases with long incubation periods the possibility of an intervening second exposure often could not be ruled out. There is little doubt, however, that extraordinarily long incubation periods do occur: in a virological examination of unexplained rabies in three United States immigrants, the isolates were variants with distinctive antigenic or genetic characteristics which matched those found in specimens of rabid animals from or near the country in which the patient had lived prior to emigration; the migrants had not returned to their country of origin with 4 years, 6 years and 11 months, respectively (King, 1998). Analysis of the incubation periods of 1555 patients revealed that although none was shorter than 10 days, 29.8 per cent were of 10-30 days'. 54.4 per cent were of 31-90 days', 14.6 per cent were of 91-365 days' and 1.2 per cent were of >365 days' duration. Factors which may influence the length of incubation period include the site of the bite (in general, the nearer the head, the shorter the period) and its severity, the degree of innervation of the bite site (bites on the face, neck, and hands are more dangerous, presumably beacause of their rich nerve supply), the quantity of virus 'inoculated' and the age and immune status of the host. The incubation period in children is purported to be shorter than that in adults and is probably assaociated with their infant stature and unusually severe or multiple bites on the face, head, and neck (King, 1998). Long incubation periods are also known for naturally infected animals and provide a mechanism for global spread of rabies variants along migratory routes and through human transport (Smith, 2002).


        3. Prognosis: Rabies is a uniformly fatal illness once symptoms begin. For cases where prompt and correct postexposure treatment is administered, no documented failures exist and patients do not develop rabies. The key to successful treatment of rabies is timing. An infected person must begin a series of immunizations as soon as possible after being bitten. If immunizations begin within two days of the bite, chances of survival are very good. Even if the immunizations do not begin until later, there is a chance that the patient can survive. The longer the delay in starting immunizations, however, the less hopeful the prognosis for recovery is. Without immunizations, a patient will almost certainly die of the disease In Wisconsin, a teenager contracted rabies from a bat bite and became the first known person to survive rabies despite not having received rabies vaccine prior to symptom onset (Krebs et al., 2005).


        4. Diagnosis Overview: Clinical Diagnosis in Humans: Diagonosis of rabies based on clinical grounds is difficult and unreliable except when specific clinical signs of hydro- or aerophobia are present. Some patients present with a paralytic or Guillain-Barre-like sybdrome or other atypical clinical features. Classical signs of brain involvement include spasms in response to tactile, auditory, visual or olfactory stimuli(e.g. aerophobia and hydrophobia) alternating with periods of lucidity agitation, confusion, and signs of autonomic dysfunction. These spasms occur at some time in almost all rabid patients in whom excitation is prominent. However, spontaneous inspiratory spasms usually occur continuously until death and their presence often facilitates clinical diagnosis. Excitation is less evident in paralytic rabies, and phobic spasms appear in only 50% of these patients. During the early stages of paralytic rabies, notable signs include myoedema at percission sites, usually in the region of the chest, deltoid muscle and thigh, and piloerection. Atypical non-classic rabies is being increasingly recognized and may be responsible for underreporting (WHO, 2002). Clinical diagnosis can be made with confidence only in cases of furious rabies where there are three major signs: fluctuating consciousness, phobic spasms, and autonomic dysfunctions. Dumb rabies is often mistaken for Guillain-Barre syndrome (Wacharapluesadee and Hemachudha, 2001). Magnetic resonance imaging performed with adequate precautions suitable for potentially infectionus patients, can be helpful in diagnosis. Abnormal, ill-defined, mildly hypersignal T2 images involving brainstem, hippocampus, hypothalamus, deep and subcortical white matter, and deep and cortical grey matter are indicative of rabies, when present, regardless of clinical types. Gadolinium enhancement is clearly shown only in later stages when patient lapse into a coma. Such a pattern differentiates rabies from other viral encephalitides, not in terms of location, but in the T2 image appearance and in the pattern of contrast enhancement when compared according to consciousness status.. Computerized tomography of the brain is of no diagnostic value (WHO, 2002). Laboratory Diagnosis: Definite diagnosis of rabies can only be made by laboratory investigations. Rabies diagnosis can be performed on fresh specimens from several diffrerent tissue sources or on appropriate specimens stored at proper temperatures, preferably refridgerated. The choice of specimens depends on the test to be performed and the stage of the disease in humans. Secretions of biological fluids (saliva, spinal fluid, and tears, can be used to diagnose rebis during life (intra vitam). Brain tissue is the prefered specimen for postmortem diagnosis in both humans and animals (WHO, 2002). The diagnosis of animal and human rabies can be made by 4 methods: (1) histopathology (2) virus cultivation (3) Serology (4) virus antigen detection. Although each of the first 3 methods have distinct advantages, none provide a rapid definitive diagnosis (WHO, 2002). (1): Histopathology - Negri bodies are pathognomonic of rabies. However, Negri bodies are only present in 71% of cases (WHO, 2002). (2): Virus cultivation - The most definitive means of diagnosis is by virus cultivation from infected tissue. Tissue culture lines, such as WI-38, BHK-21, or CER. Since rabiesvirus induce minimal CPE, IF is routinely used to detect the presence of rabies virus Ag in the tissue culture. The more commonly used method for virus isolation is by the inoculation of saliva, salivary gland tissue and brain tissue intracerebrally into infant mice. The mice should develop paralysis and death within 28 days. Upon death, the brains are examined for the presence of the virus by immunofluorescence (WHO, 2002). (3): Serology - circulating antibodies appear slowly in the course of infection but they are usually present by the time of onset of clinical symptoms. The most commonly used serological tests were the mouse infection neutralization test (MNT) or the rapid fluorescent focus inhibition test (RFFIT). These tests have now been largely superseded by EIAs. Serology had been reported to be the most useful method for the diagnosis of rabies (WHO, 2002). (4): Rapid virus antigen detection - in recent years, virus antigen detection by IF had become widely used. The potentially infected tissue is incubated with fluorescein-labeled antibody. The cells are examined by fluorescent microscopy for the presence of fluorescent intracytoplasmic inclusions. The specimens which are usually used are corneal impressions (obtained by gently abrading the cornea with a microscopic slide) or neck skin biopsy (the cells examined are the sensory nerves). In an American series, IF of corneal impressions or neck skin impressions was diagnostic only in 50% of cases early in the course of the clinical illness (WHO, 2002). Clinical diagnosis is not difficult if there is a documented history of exposure and subsequent compatible clinical signs or symptoms. However, because an exposure history may be lacking, rabies should be considered in any acute, unexplained neurological disease of suspected viral origin that rapidly progresses to coma and death. Routine diagnosis is established by standard laboratory tests for specific virus isolates, antigens, nucleic acids or VNA. Postmortem diagnosis should be performed on CNS specimens, especially the brainstem, hippocampus, and cerebellum. The fluorescent antibody test and the avidin-biotin immunohistochemical technique are sensitive and specific methods for detecting virus antigen. Antibodies, particularly those that recognize particular epitopes of the N protein, are useful because they provide consistently reliable results, even if the tissues have been fixed with formalin or embedded in paraffin. Examination of skin biopsies from the face or hair covered occipital portions of the neck for virus antigen is a rapid method to diagnose human rabies before death. Rabies virus can be isolated from saliva by direct intracerebral inoculation into mice or by infection of neuroblastoma cells. Fluorescent antibody examinations of corneal impressions may also occasionally lead to the diagnosis of human rabies. The reverse transcription-polymerase chain reaction assay (RT-PCR) has been used to amplify and sequence parts of the lyssavirus genome directly from brain, saliva, and other affected tissues. This not only allows detection of rabies virus-specific RNA but also permits insights into the identity of the virus variant by genetic sequencing. Detection of VNA in serum late in clinical course can be diagnostic for rabies, if the patient has not been previously vaccinated. Except for certain cases of postvaccinal encephalomyelitis, CSF antibodies are produced only in rabies-infected, not in vaccinated individuals (de Mattos et al., 2001).


        5. Symptom Information :
          • General Description: In general, the clinical disease can be divided into three phases: (1) Prodromal phase, (2) Excitation phase, furious rabies or acute neurologic phase, and (3) Paralytic phase, dumb rabies or coma preceding death. However, these phases may not be distinct, as some of the early phases are not always apparent (Woldehiwet, 2005).
          • Syndrome -- Prodromal Phase:
            • Description: During the prodromal period, lasting 2 to 10 days, symptoms are usually mild and almost entirely nonspecific and include general malaise, chills, fever, headache, photophobia, anorexia, nausea, vomiting, diarrhea, sore throat, cough, and musculoskeletal pain. One specific early symptom is abnormal sensation around the bite site, such as itching, burning, numbness, or paresthesia (de Mattos et al., 2001) The prodromal stage is often characterized by a marked change of behaviour in dogs, cats and other pets, which normally are friendly and exhibit predictable behavioural patterns. This is also true with free living animals, which may loose their natural instinct to be afraid of man and to be less visible. The clinical signs of rabies in other animals are not always as distinct as in dogs, but in general, the disease is characterized by a progressive dysfunction of the CNS. However, the clinical signs can be easily mistaken with those of other infections that cause encephalomyelitis or other neurological manifestations and from poisoning or toxicoses with neurological syndromes. In man, the early (prodromal) stages of the disease may be characterized by loss of appetite, headache, general aches and pains and other influenza-like symptoms. These early symptoms are difficult to differentiate from other causes, but the history of exposure to a rabid animal is an important consideration. Often overt clinical signs of rabies start by itching or stabbing pains or abnormal sensations at the site of the bite. Local neuropathic pains at the bite site described as burning, numbness, tingling or itching are reported to be more common in bat-related infections. Victims may also suffer from insomnia and anxiety, the fear of death exasperating the situation (Woldehiwet, 2005).


              • Symptoms Shown in the Syndrome:

            • Abnormal sensation (de Mattos et al., 2001):
              • Ontology: UMLS:C0423571
              • Description: One specific early symptom is abnormal sensation around the bite site, such as itching, burning, numbness, or paresthesia (de Mattos et al., 2001).
            • Anorexia (de Mattos et al., 2001):
              • Ontology: UMLS:C0003123
            • Anxiety (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0003467
            • Chills (de Mattos et al., 2001):
              • Ontology: UMLS:C0085593
            • Cough (de Mattos et al., 2001):
              • Ontology: UMLS:C0010200
            • Diarrhea (de Mattos et al., 2001):
              • Ontology: UMLS:C0011991
            • Dilated pupils:
              • Ontology: UMLS:C0026961
            • Depression (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0344315
            • Excessive salivation (Wiktor and Hattwick, 1977):
              • Ontology: UMLS:C0037036
            • Fever (de Mattos et al., 2001):
              • Ontology: UMLS:C0015967
              • Description: A low fever, malaise, headache, anorexia, nausea and sore throat are common
            • Headache:
              • Ontology: UMLS:C0018681
              • Description: In man, the early (prodromal) stages of the disease may be characterized by loss of appetite, headache, general aches and pains and other influenza-like symptoms (Woldehiwet, 2005).
            • Hyperesthesia:
              • Ontology: UMLS:C0020453
              • Description: Hyperesthesia, an increased sensitivity to bright light and loud noise, excessive salivation, lacrimation and perspiration have been noted. The general muscle tone may be increased, and facial expression can be overactive
            • Irritability (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0022107
            • Lacrimation ():
              • Ontology: UMLS:C0423153
            • Malaise (de Mattos et al., 2001):
              • Ontology: UMLS:C0231218
            • Melancholia ():
              • Ontology: UMLS:C0025193
            • Nausea (de Mattos et al., 2001):
              • Ontology: UMLS:C0027497
            • Nervousness:
              • Ontology: UMLS:C0027769
              • Description: There may be increasing nervousness, anxiety, irritability, depression, melancholia, with or without a sense of impending death (Hattwick and Gregg, 1975).
            • Perspiration (Wiktor and Hattwick, 1977):
              • Ontology: UMLS:C0038990
            • Photophobia (de Mattos et al., 2001):
              • Ontology: UMLS:C0085636
            • Shallow respiration (Wiktor and Hattwick, 1977):
              • Ontology: UMLS:C0221161
            • Sore throat (de Mattos et al., 2001):
              • Ontology: UMLS:C0242429
            • Vomiting (de Mattos et al., 2001):
              • Ontology: UMLS:C0042963
          • Syndrome -- Excitation phase, Furious rabies or Acute neurologic phase:
            • Description: During the acute neurologic phase, patients exhibit signs of nervous dysfunction such as anxiety, agitation, dysphagia, hypersalivation, paralysis and episodes of delirium. Occasionally, priapism or increased libido may be observed. Cases in which hyperactivity is predominant are classified as "furious" rabies. In furious rabies, the neurologic period ends in 2 to 7 days with coma or sudden death from respiratory of cardiac arrest (de Mattos et al., 2001). During this stage, the victim may develop the classical signs of hydrophobia, aerophagia and general irritability (Woldehiwet, 2005). Cardinal features of furious rabies, fluctuating consciousness, hydro- or aerophobia and inspiratory spasms, signs of autonomic dysfunction, were seen in all Thai furious rabies patients. In noncanine rabies endemic areas, such as in North America, where bats are the principle vector of rabies, clinical expression may be variable (Hemachudha et al., 2005).


              • Symptoms Shown in the Syndrome:

            • Bradycardia:
              • Ontology: UMLS:C0428977
            • Seizures (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0036572
            • Constipation:
              • Ontology: UMLS:C0009806
            • Constriction of the pupils:
              • Ontology: UMLS:C0728710
            • Dilation of the pupils:
              • Ontology: UMLS:C0026961
              • Description: Dilation or constriction of the pupils that may be asymmetric and associated with: (1) Hippus (abnormal exaggeration of the rhythmic contraction and dilation of the pupil, independent of changes in illumination or in fixation of the eyes). (2) Nystagmus (continuous rolling of eyeball). (3) Diplopia
            • Hoarseness (Burton et al., 2005):
              • Ontology: UMLS:C0019825
            • Hydrophobia:
              • Ontology: UMLS:C1609481
              • Description: Hydrophobia or the fear of water appears to develop in most cases of human rabies. Attempts to drink water or eat may produce severe painful spasms of the pharynx and larynx and precipitate an episode of hyperactivity which seems to be extremely frightening to the patient. Once experienced, the sight, sound or smell of liquids may provoke the syndrome. The ensuing choking may cause severe apnea (temporary cessation of breathing) and cyanosis. Death frequently occurs during the course of such a convulsive attack. Dehydration is a common consequence (Wiktor and Hattwick, 1977).
            • Papilledema (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0030353
            • Strabismus:
              • Ontology: UMLS:C0038379
              • Description: Strabismus - failure of the eyes to follow one another in any movement. This is due to incoordination of the extra-ocular muscles (Hattwick and Gregg, 1975).
            • Tachycardia (Hattwick and Gregg, 1975):
              • Ontology: UMLS:C0039231
            • Urinary Retention:
              • Ontology: UMLS:C0080274
            • Weakness of facial muscles (Burton et al., 2005):
              • Ontology: UMLS:C0427055
          • Syndrome -- Paralytic phase, Dumb rabies or Coma preceding death:
            • Description: When paralysis dominates, it is classified as paralytic or "dumb" rabies. Paralytic rabies can occur in about 20% of patients and may occur more frequently in persons exposed to certain variants, such as vampire bat rabies virus strains. In marked contrast to furious rabies, the sensorium is largely spared. Patients initially develop paresthesia and weakness, and finally flaccid paralysis, usually in the bitten extremity. Paralysis progresses to paraplegia and quadriplegia. In paralytic rabies, the course is usually less progressive, with some patients living up to 30 days without intensive care. The final stage of the disease is coma, which lasts 3 to 7 days and results in death. In patients receiving respiratory assistance, survival may be prolonged for weeks, with death caused by other complications (de Mattos et al., 2001). Only one or two classical signs of rabies, or even none, may be seen during the whole clinical course in paralytic rabies. Consciousness was preserved until the preterminal phase. Hemachudha and Wacharapluesadee reported phobic spasms in only half of 35 confirmed paralytic rabies patients between 1988 and 2004. Weakness was the initial manifestation in paralytic rabies, whereas this was noted only when furious rabies patient approached coma (Hemachudha et al., 2005). The paralytic form of the disease, without the classical signs of hydrophobia, is more common and needs to be differentiated from other conditions. For example, some patients may present with paralytic or Guillain-Barre-like syndrome, without the typical excitation, spontaneous inspiratory spasms and hydrophobia (Woldehiwet, 2005).


              • Symptoms Shown in the Syndrome:

            • Hydrophobia:
              • Ontology: UMLS:C1609481
              • Description: Hydrophobia, if present, disappears and swallowing becomes possible, although difficult, as the paralytic phase sets in. A progressive, general, flaccid paralysis develops. Apathy shades into stupor, progressing to coma. There is urinary incontinence. Peripheral vascular collapse ensues and death follows (Wiktor and Hattwick, 1977).

        6. Treatment Information:
          • Rabies Immune Globulin (RIG): Rabies immune globulin is a sterile, concentrated nonpyrogenic solution containing antirabies antibodies prepared from plasma of adults immunized with rabies vaccine. The manufacturers and the US Public Health Service Advisory Committee on Immunization Practices (ACIP) currently recommend that post exposure prophylaxis following rabies exposure include immediate and thorough wound treatment (e.g. cleansing all bite wounds and scratches with soap and water and irrigation with a virucidal agent such a providence iodine solution) and, for previously unvaccinated individuals, passive immunization with RIG combined with active immunization with rabies vaccine. RIG is commercially available in the US as BayRab and Imogam Rabies-HT, and the ACIP states that both preparations of RIG are considered equally effective when used as recommended ( AHFS, 2005a).
            • Applicable: Rabies immune globulin (RIG) is used to provide passive immunity to rabies as part of a post exposure prophylaxis regimen in individuals exposed to the disease or virus who previously have not been vaccinated against rabies ( AHFS, 2005a).
            • Contraindicator: Repeated doses of RIG are contraindicatedonce active immunization with rabies vaccine has been initiated since repeating the dose of RIG may partially suppress active production of antibody and interfere with maximum production of immunologic response to the vaccine. The manufacturers state that serious systemic reactions to preparations may occur following inadvertent IV administration of RIG. Although systemic reactions to preparation containing immunoglobulins are rare, epinephrine should be available for treatment of acute anaphylaxis if it occurs. RIG should be administered with caution to individuals with a history of prior systemic allergic reactions to human immune globulin preparations. In addition RIG should be administered cautiously to individuals with a specific IgA deficiency, since these individuals may have serum antibodies to IgA ( or develop antibodies following administration of RIG) and anaphylaxis could result following administration of RIG or other blood products containing IgA. RIG should be used with caution in individuals with thrombocytopenia or bleeding disorders, since bleeding may occur following IM administration of the drug ( AHFS, 2005a).
            • Complication: Rabies immune globulin (RIG) has been reported to partially supress the active antibody response to rabies vaccine. When anatomically feasible, the full dose of RIG should be thoroughly infiltrated in the area around and into the wound(s) and the remaining volume should be administe