Rabies is a potentially fatal viral disease affecting the central nervous system of dogs. It is a mammalian disease, and can occur in any animal of this group, but mostly carnivores, including man, are affected. The rabies virus that causes this disease inhabits the nerve tissue as well as the salivary gland, and gets passed on to others through the bite of an infected animal. The disease is fatal once the symptoms appear in a bitten animal or man.
Rabies has a worldwide distribution, except for a few isolated islands and countries like Japan who have been able to eradicate the disease completely. Even though strict quarantine measures have been successful in greatly reducing the infection in dogs in Europe and North America, the wild animals still remain reservoirs of the virus.
The virus present in the saliva of a rabid animal gets introduced into another animal or man through bite wounds. The virus may remain in the bitten animal for several days to a few months before the typical symptoms of the disease appear. This period of incubation may vary in different animals, but it usually takes 3 weeks to 3 months for dog to show symptoms.
Symptoms and Diagnosis
Symptoms appear when rabies affects the central nervous system of the dog. Sudden changes in behavior and temperament, often accompanied by partial and progressive paralysis are typical. The dog may show irritability, loss of appetite and nervousness. Uncharacteristic behavior such as an unfriendly dog becoming suddenly friendly as well as a friendly one becoming aloof is common. Hyperexcitability is another typical symptom. The dog may become aggressive even towards its owner and other familiar people. Rabid wild animals lose their fear and inhibitions and wander into human inhabitations. Nocturnal animals may be seen running about at any time of the day.
Rabies may appear in two entirely different forms such as the furious form and the paralytic form.
When it appears in the furious form in dogs, the common name “mad-dog” is apt. Other species of animals and people also display the furious form. The dog becomes extremely irritable and aggressive, biting and clawing viciously at everything nearby. It would stand alert, with dilated pupils and an anxious expression, ready to attack at the slightest movement or sound. A normally docile dog may become fearless and approach bigger animals and people and may launch an attack. Rabid puppies may become overfriendly to people, but may start biting when petted. It may initially appear as playfulness, but gradually becomes more aggressive. After this stage, the rabid animal may lose muscle coordination, and have seizures, followed by paralysis that may progress steadily until death.
If the dog develops the paralytic form of the disease, its throat as well as jaw muscles become paralyzed, making it difficult for the dog to swallow food. The lower jaw may be drooping, accompanied by copious salivation. Aggressiveness and vicious biting and clawing may be completely absent. They can still transmit the disease through the saliva which contains the virus. Anyone who comes in contact with the saliva during an attempt to feed the animal or by handling the objects that have been contaminated with it can acquire the infection. The paralysis is progressive and becomes total, culminating in death.
The initial symptoms of rabies can be easily mistaken for other common disorders of the nervous system, and the diagnosis is not always easy. In places where rabies is not prevalent, the possibility may be overlooked, and the aggressiveness may be ascribed to the nature of the dog. When rabies is suspected, further laboratory tests are conducted to confirm the diagnosis. Euthanasia is the best option – and often the only option- when the dog is confirmed to be rabid. An autopsy may be done and the brain tissue of the dog may be analyzed in the laboratory.
Guidelines for controlling rabies have been outlined by the World Health Organization. They are mainly aimed at reducing the risk of disease transmission between dogs and between the dogs and people.
According to the WHO guidelines the following measures have to be taken:
- Suspected cases of rabies to be notified, dogs with confirmed disease or typical symptoms or and those bitten by them to be euthanized
- Quarantine and leash laws applied for dogs susceptible to the infection
- Immunization measures in animals and people
- Control of stray dogs including euthanizing unvaccinated unclaimed dogs
- Registration laws for all dogs
In most countries, vaccination against rabies is strictly followed. The vaccination schedule recommended by the Compendium of Animal Rabies Control is first two doses 1 year apart, followed by revaccination every third year.
Management of Suspected Rabies Cases
Wherever rabies exists in the wild animals, the domesticated animals, including dogs and cats are at risk of exposure. If a dog is bitten by a bat or other mammalian carnivores, the dog should be considered as a suspect case of rabies as long as the animal that bit it is not available for testing.
According to the National Association for State Public Health Veterinarians, if the dog is not vaccinated prior to exposure, it has to be euthanized. In case the owner does not agree to it, the dog should be isolated away from all other animals and humans for a period of 6 months. One month prior to its release, it should be vaccinated against rabies too. In cases where a vaccinated dog is bitten, it should be kept in isolation and close observation for a period of 45 days after revaccinating it.
Risk of Infecting People
Exposure to a rabid dog or one suspected to have the disease should be considered a serious risk. Exposure to rabies through the bite of wild animals should be considered for immediate post-exposure vaccination even if symptoms of the disease has not been observed in the animal as it is not possible to test that animal.
If a person is bitten by a domesticated animal such as a cat, ferret or dog, post-exposure vaccination should be initiated in spite of the vaccination status of the animal. The animal should be isolated, leashed, and observed for a period of 10 days for any clinical symptoms of rabies. If any signs are observed it should be euthanized. All other animals and people who have come in contact with the animal should be vaccinated as well. In case of a stray animal, it is euthanized immediately after the 10-day observation period.
All veterinary staff, animal breeders, animal control personnel and laboratory workers handling rabies testing should have pre-exposure vaccination. It is recommended for people who travel to countries with prevalence of canine rabies, as well as for those who frequent wild areas where the disease may be present in mammalian carnivores.