DESCRIPTION OF THE RABIES VIRUS
Rabies results from an infection by the neurotropic Rabies Virus, of the order Mononegavirales, family Rhabdoviridae and genus Lyssavirus. This thumb shaped virus measures approximately 60 to 70 nm x 180 nm. It is an enveloed, negative sense, non segmented and single stranded RNA virus, classified as genotype 1, serotype 1 in this genus. There are many strains of the Rabies Virus and each strain is maintained in particular reservoir host(s). Although these viruses can readily cause Rabies in other species, they usually die out during serial passage in species to which they are not adapted. Closely related Lyssaviruses, which can cause a neurological disease that is identical to Rabies are known as Rabies-related lyssaviruses or non Rabies Lyssaviruses.
STRUCTURE OF THE LYSSAVIRUS
The primary causative of the diseases is the Rabies virus belonging to the genus Lyssavirus. Based on genetic homology, the Rabies virus and the Rabies Related Lyssaviruses have been classified into 3 phylogroups. Phylogroup I contains the Rabies Virus, Duvenhage Virus, European Bat Lyssa Virus 1, European Bat Lyssa Virus 2, Australian Bat Lyssa Virus, Irkut Virus, Aravan Virus, Khujand Virus and Bokelo Virus. Phylogreoup II includes Logos Bat Virus, Mokola Virus and Shimoni Bat Virus. Phylogruop III consists of the West Caucasian Bat Virus and the Ikoma virus.
The Rabies Virus is readily transmitted between mammals, irrespective of the animal genus or species. The Rabies Virus is maintained in two epidemiological
cycles, namely, the urban and the sylvatic. In the urban cycle, dogs
are the primary reservoir host. This cycle predominates in most of the developing countries of Africa,
Asia, Central and South America where the population of unvaccinated and
semi-owned or stray dogs and cats are relatively high. Other domestic livestock such as cattle, goats, sheep and swine which acquire the infection through a cat or dog bite might easily pass on the infection to susceptible human beings.