Rabies awareness and cure

Pashu Sandesh, 15 July 2021

Aishwarya Lade, Himani K., Smita Bordoloi, Poonam Shakya, Joycee Jogi,

Ajay Rai and Anju Nayak

Department of Veterinary Microbiology, Co.V.Sc. & A.H., NDVSU, Jabalpur

Rabies is a neurological disease of mammals that is almost invariably fatal once the clinical signs develop. Animals and Humans are usually infected when they are bitten by an infected animal, or exposed to its saliva or central nervous system (CNS) tissues. Although rabies is generally well-controlled among domesticated animals in developed nations, canine rabies continues to be a serious problem in some areas of India. Wildlife reservoirs have become increasingly important where canine rabies is under control. Rabies can be effectively treated if the exposure is recognized before the symptoms develop. However, people in impoverished countries do not always have access to post-exposure prophylaxis, and even in nations with good medical care, cases occur occasionally in people who do not realize they were exposed.

Etiology

 Rabies results from infection by the rabies virus, a neurotropic virus in the genus Lyssavirus, family Rhabdoviridae. It is classified as genotype 1, serotype 1 in this genus. There are many strains of the rabies virus; each strain is maintained in a 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. 

Geographic Distribution With some exceptions (particularly islands), the rabies virus is found worldwide. According to the World Health Organization (WHO), a country is considered to be free of rabies if there have been no indigenously acquired cases in humans or animals during the previous 2 years, in the presence of adequate surveillance and import regulations. 

Transmission 

The rabies virus is readily transmitted between mammals, whether they are the same or different species. This virus is usually spread in the saliva when an infected animal bites another. Less often, an animal or person is infected by contact with infectious saliva or neurological tissues, through mucous membranes or breaks in the skin. The rabies virus is not transmitted through intact skin. There are also rare reports of transmission by other routes. , people who drank unpasteurized milk from rabid cows were given post-exposure prophylaxis. Pasteurized milk and cooked meat are not expected to pose a risk of infection, as the rabies virus is inactivated by heat; however, as a precaution, the National Association of State Public Health Veterinarians recommends against consuming tissues and milk from rabid animals.

Prevention

Rabies can be prevented in domesticated animals by vaccination and by the avoidance of contact with rabid wild animals. Rabies vaccines are available for dogs, cats, ferrets, cattle, sheep and horses. Both inactivated and modified live vaccines are effective, but rare cases of post-vaccinal rabies have been reported with the modified live vaccines in dogs and cats. Vaccines have not been validated in rabbits or rodents, although they might be used extra-label in petting zoos or other facilities where animals are in contact with many people. Wild animals can be immunized with oral vaccines distributed in a bait.

In countries with large stray dog populations, similar vaccines may be useful. Conventional rabies vaccines do not seem to protect animals against rabies-related viruses in phylogroup II (Mokola virus and Lagos bat virus); these viruses have caused fatal diseases in vaccinated animals. Some cross-protection seems to exist with rabies-related viruses in phylogroup I.

Preventing animals from roaming will reduce the risk of exposure to rabid wild animals. To protect pet rabbits and rodents, they should be housed indoors, and watched closely if they are allowed outside to exercise. Rabbits kept outside should be kept in an elevated, double-walled hutch that does not have exposed wire mesh floors. As much as possible, domesticated animals should be kept away from contact with wildlife, especially those that behave unusually. Bats caught by cats should be submitted for rabies testing. To prevent the transmission of rabies to humans or other animals (as well as to prevent unnecessary prophylaxis in people who have been exposed), unvaccinated animals that have been exposed should be euthanized and tested. Alternatively, they may be placed in strict isolation for 6 months, with vaccination of dogs, cats and ferrets either upon entry into isolation or 1 month before release. Livestock, rabbits and other animals are isolated but not necessarily vaccinated. Vaccinated animals are revaccinated and confined under observation for at least 45 days. Animals with expired vaccinations are evaluated on a case-by-case basis. Asymptomatic dogs, cats or ferrets that have bitten humans (with no history of exposure to rabies) are currently observed for 10 days.

Treatment

There is no treatment once the clinical signs appear. Few studies have been published on postexposure vaccination protocols for animals, and these procedures are often considered to be inadvisable because they may increase human exposure. Post-exposure prophylaxis of livestock and pets, using commercial vaccines licensed for this purpose, is practised in some Asian countries including India.