Veterinary Advice Online: Rabies Virus.

The information contained within this article covers a range of topics designed to fully educate pet owners about rabies virus in dogs, cats and other domestic and wild animal species. Topics on vaccination of pets, side effects of rabies vaccines and human health implications of rabies are also covered. For the Australians among us, information on bat Lyssavirus (Australian rabies) has also been added. The information presented is detailed (but still easy to understand) because we are aiming to educate owners and the public thoroughly and to provide them with enough information that they might be better informed and able to troubleshoot problems with their own pets. The topics are covered in the following order:

1) What is rabies? - this is a short definition and basic explanation of what rabies is.

2) Which animals are at risk of contracting this virus?

3) Transmission - How do pet animals and humans catch this disease? - this section contains information about where and how animals and people can contract rabies and the environments and occupations that are higher in risk.

4) Symptoms and Signs - What does this virus do to dogs, cats, humans and other animals? This section contains the following subsections:
4a) How do rabies viruses work (how do they replicate and destroy cells etc.)?
4b) How does rabies affect the brain (what neurological symptoms of rabies are seen)?
4c) How does rabies affect the salivary glands (how is rabies spread)?
4d) Rabies vaccine-associated diseases (rabies caused by vaccines).

5) Testing and Diagnosis. This section contains the following subsections:
5a) Obtaining a sample to test - includes sections on euthanasia of rabid animals; how to capture and confine a rabid animal; how to store deceased animals prior to sending them to the lab.
5b) The fluorescent antibody test for rabies.
5c) Mouse inoculation.
5d) Rabies PCR.
5e) Rabies antibody testing.
5f) Negri bodies.

6) How is this disease treated? This section contains the following topics:
6a) What to do with a clinically rabid animal.
6b)What to do if an unvaccinated pet is bitten by a suspect rabid animal.
6c) What rabies treatment is available if a vaccinated pet is bitten by a suspect rabid animal.

7) What is the prognosis for this virus?

8) Prevention of the disease. This section contains the following subsections:
8a) Animal vaccination protocols and schedules (includes some rabies vaccine reaction and side effects info).
8b)Human vaccination protocols (includes information on which people and occupations need the rabies vaccine)
8c) Reducing your exposure to rabies (includes info on what you and your local authorities can do to reduce the risk of people and pets encountering rabid animals).

9) Rabies in humans. This section contains information on what vaccinated and unvaccinated people need to do if they are bitten or scratched by a suspect rabid animal. It contains info about post-exposure prophylaxis in people and when it may be required.

10) Considerations when importing and exporting animals from and to affected zones.

11) Rabies-virus links.


1. What is Rabies?

Rabies is a severe, fatal disease affecting the nervous system and salivary glands of dogs, cats, humans, livestock and a wide range of wild mammal species (foxes, wolves, raccoons, skunks and certain species of monkey, bat, civet and mongoose tend to be the sylvatic (wild) species most frequently implicated in the carriage and spread of rabies). The disease, which has no cure, is caused by a virus of the family Rhabdoviridae, a family which includes several genera one of which, the genera Lyssavirus, contains rabies and also Australian Bat Lyssavirus (ABLV).

Animals affected by the disease usually die from a range of severe neurological signs. Some will froth at the mouth and drool and make a choking sound, because of an inability to swallow; some animals will become atypically docile; others will become crazy and restless and race around in a mad, disoriented way biting objects and other animals and the air (the classical rabid animal sign - termed furious rabies); some animals will seizure and die and others will progress to a depressed, paralysed state: unable to move or get up or feed (the paralytic form of rabies), before drifting into a coma and dying. Wild animals affected with the virus may initially appear 'very tame' or be active outside of their normal waking hours (e.g. nocturnal animals may appear in daylight hours), before progressing to the furious and/or paralytic forms of disease. The neurological symptoms of rabies and the way in which they progress to become fatal are discussed in detail in section 4b.

Spread by the bite or scratch of infected wild and domestic animals, rabies is a highly contagious disease and one of the animal diseases of major zoonotic risk to the human public. Rabies is found in many countries of the world, including the United States of America, India, much of Europe and also the tropical zones of Africa, South America and Asia. In some of these regions, vaccine and animal control programs have been initiated to protect the humans and domestic animals living there. The disease is high on the list of severe notifiable diseases in countries (e.g. Australia, Great Britain, Japan and many island nations) that don't yet have it.


2. Which animals are at risk of rabies?

Most non-vaccinated warm-blooded animals of any age group have the potential to contract and die from rabies, however, only certain mammalian species have been found to actually replicate the virus inside them in a way that allows for the spread of rabies from animal to animal (note, the ability of different mammalian species to pass rabies on to other species is variable and is discussed in section 3 - the transmission of rabies).

Domestic mammalian animals:
All domestic mammalian species have the ability to contract rabies. The dog and cat are obvious and well-known (remember the movies Cujo and Old Yeller, anyone?), but pet ferrets, rabbits and pet rodents can be affected too. Domesticated livestock animals (pigs, cows, sheep, horses, camelids) can also contract and pass on the disease to other animals and humans.

Wild mammalian animals:
Because most domesticated animals in rabies endemic developed countries are vaccinated and thus somewhat protected from contracting or spreading rabies, the main source of rabies infection for humans and their pets and livestock comes from the rabies-infected wild animals that exist in the local area. Unvaccinated domestic animals and humans that get bitten by rabid wild animals can contract the fatal disease.

As with the domesticated animals, any mammalian wild animal species can be potentially affected by rabies. Wild carnivores (all members of the dog, fox, weasel, cat, civet, skunk, mongoose, raccoon and bat family) are the wild animal species most commonly implicated in rabies infection and rabies transmission to man, but other wild mammals can also contract and die from the disease. Wild and feral ruminants (cattle, sheep, goats etc.) and pseudoruminants (camels, alpacas, llamas etc.) can contract rabies, as can mammals like monkeys, rabbits, hares and a wide range of rodents (beavers, cavies, squirrels). As is discussed in section 3, the ability of these various species to pass this disease on to other animals and man may vary.

The wild animals which are most likely to be infected with rabies, and which are of most risk to humans and their pets, varies from region to region and country to country and is directly dependant on factors such as:
a) the strain of the rabies virus (certain strains of rabies 'favour' certain wild hosts);
b) the populations of wild animals around;
c) the wild animals' virus susceptibility;
d) the amount of virus shed in their saliva and
e) the location and distribution their natural territories relative to man's.

For example, in regions of the USA that are more human-populated and built-up (e.g. suburban zones, population-dense townships, outer city regions) rabies infection is more likely to come from wild animals that have adapted to close-living with humans (raccoons, skunks, bats and red and grey foxes). In the cold Alaskan wilderness, you are unlikely to find significant populations of red foxes and raccoons and so the main source of infection is likely to be Arctic foxes and wolves. In other countries, native wolf and fox populations may have been so decimated by environmental destruction and hunting that another species has stepped into the gap to become the prominent rabies carrier. Some of the countries in Africa and South America don't have the types of wild rabies-carrier species typically seen in Europe and the USA and so an entirely different species, common to the area, has taken up the role of major rabies reservoir (e.g. monkeys, bats, mongooses, civets, cattle).

Non-mammalian species and rabies:
Rabies has been experimentally found to infect and kill a number of non-mammalian warm-blooded species, including birds. Although the virus will infect these species, only mammalian species are