Rabies Virus

Transmission and Succeptible Hosts

Rabies is able to infect warm blooded mammals. The disease manifests neurologically since its tropism is for neuronal tissue.  Although this infection is able to contaminate the whole array of mammalian hosts the reservoirs of this contagion in most regions are maintained by bats, raccoons, skunks, and various other wild and domestic canines. The virus mutates and specific strains are more stable in certain hosts. The species of reservoir host depends on the region of the world and clearly has important considerations for control of the virus. For example in Europe, foxes carried the infection endemically. The institution of oral or aerial vaccination programs has led to a dramatic decrease in rabies incidence in these populations.
Although rabies virus causes neurological disease, it is concentrated in the saliva of the infected animal and therefore the most common route of transmission for the virus is following a bite wound from an infected animal.  Here it replicates and by its predilection for nervous tissue, it invades the peripheral nerve endings utilizing the glycoprotein on its viral envelope. It then ascends to the central nervous system by fastening itself on its host cell machinery. The process of reaching the brain takes time and this is known as the incubation period.  With rabies infections, the incubation period can vary widely.  Some sources suggesting clinical signs may appear as early as 2 weeks after infection, to as late as 1 year after the initial insult. During this time there are no clinical signs in the infected animal.
 
Other methods of rabies infection transmission are extremely rare.  The virus can be aerosolized and bind to the olphactory nerve endings in the nasal cavity or by other uncommon means of attachment to injured mucus membranes or during human transplant surgical procedures.
 

In the veterinary clinic setting, procedures to kill the remaining viral contaminates can easily be accomplished since rabies is susceptible to many disinfectants. If contaminated saliva is in your clinic it can be efficiently neutralized with commercially available products.

Once the virus reaches the brain it causes an acute encephalitis or myelitis when it infects the spinal cord and is invariably fatal.   The clinical manifestations of this disease will be evident within 3-5 days of reaching the brain and salivary excretion begins once objective signs are evident. The virus gets to the saliva quickly by following along the peripheral nerve routes directly to salivary glands. Viral shedding is possible in the saliva prior to onset of clinical signs.