An introduction to Rabies (Hydrophobia)
- Part 5 -

Dr Asem Suresh Kumar Meitei *

Once the symptoms of rabies develop, treatment of ant form is useless. Until now, treatment of rabies means treatment of exposed individuals with a course of suitable antirabies vaccine. Recently, drugs like Doxuridine, Vidarabine and Acyclovir are reported to be useful in the treatment of exposed cases of rabies before development of clinical symptoms. These drugs are not yet available in India.

In an enzootic country like India, every case or individual bitten by a carnivorous animal should be treated for rabies without any doubt. Treatment should commence within seven days of exposure. Even, anti-rabies vaccinated (prophylactically) dog has been bitten by a suspected rabid dog, it should also be treated for rabies.

Treatment

1) No treatment should be attempted after clinical signs are evident. Immediately after exposure irrigation of the wound with 20% soap solutions or a solution of Zephiran (bezalkonium chloride) may prevent the establishment of the infections. Post–exposure vaccination is unlikely to be of value in animals, as death usually occurs before appreciable immunity has had time to develop.

2) Euthanasia of suspect animals must be prevented, particularly if human exposure has occurred, since the development of the disease in the animals is necessary to establish a diagnosis.

3) For the treatment of animals, phenol or beta-propiolactone inactivated five percent sheep brain tissue anti rabies vaccine made with the classical Pasteur (Paris) or Flury or Kelev strain is used.

4) The Pasteur (Paris) strain of virus is the one which was originally used by Pasteur and his co-workers for preparation of ARV.

5) Flury strain of rabies virus was isolated from a girl, Flury, who died of rabies after exposure to the licks in a wound by a rabid dog.

6) Kelev strain was isolated from a rabid dog.

These are fixed virus and suitable for production of ARV.

The same vaccine is used in humans. Use of brain tissue vaccine in human has a disadvantage in the form of post-vaccinalneuro—paralytic reaction. A human diploid cell inactivated rabies vaccine is available for treatment of man exposed to rabies.

While treating individuals, especially man, with brain tissue ARV, special attention should be given for a reaction, known as post–vaccinalneuro-paralytic paralytic reaction. The symptoms provoked are of the nature of allergic responses.

Acute urticarial, syncope and oedema may occur soon after an injection in individuals who have been sensitized by a previous injection. But in those who have not been treated before, symptoms of erythema a, oedema, pruritus and pain may develop around the site in about a week.

Prophylactic anti rabies vaccination is used in India usually in dogs, cats and other carnivorous pet animals. In some countries of the Latin America and Islands of the Caribbean sea cattle as well as humans are prophylactically vaccinated with ARV. This has to be done in these places due to prevalence of a blood sucking bat, known as vampire bat, which acts as a vector and reservoir of rabies.

For prophylactic vaccination ARV of 20 percent strength of sheep brain tissue is used. First vaccination should be done at the age of six months. The second dose vaccine after six months of the first vaccination and then annually to be done.

Prevention & Control

The complete details of programmes for rabies control include control of the disease in dogs, other domestic animals, wildlife and bats, etc.

1) Vaccination against rabies and registration of cats and dogs.
2) Promotion of responsible animal ownership
3) Management of stray animal populations
4) Oral vaccination of wildlife reservoirs, if possible where there is a high risk of the disease.
5) Mass Education to avoid exposure to suspect rabid animals

For prevention and control of rabies in a country like India where dog is the most important vector, the following measures of restraint and control should be applied, when rabies has made its appearance.

1) Destruction of all rabid dogs, and the seizure of all biting dogs or of dogs suspected of being infected. These should be placed in quarantine under proper veterinary supervision for at least two weeks. If symptoms of rabies become manifest the affecting dog should be destroyed and its head or brain be submitted for laboratory examination.

Ø The seizure and destruction of all other wandering and ownerless dogs.
Ø Stray dog control and euthanasia of unvaccinated dogs with low levels of dependency on, or restriction by, people
Ø The compulsory vaccination of all other dogs with a reliable and potent vaccine.
Ø During the period immunization and as long as rabies prevails all dogs should be muzzled and confined to their respective homes.
Ø The registration of all dogs and the imposition of a dog tax in order to defray part of the expenses associated with the application of the control measures.
Ø Dogs known to have been exposed to rabies must be either destroyed or placed under veterinary observations in quarantine for a period of at last six months.
Ø The importation of dogs should not be permitted unless arrangements can be made for their confinement in quarantine under veterinary supervision for a period of not less than six months.
Ø Dogs under six months old are particularly susceptible and are not readily immunizable, and should, therefore be kept under strict supervision until the area is free from rabies.

For farm animals, there are two useful control techniques: (1) Prevention of exposure: It can be achieved to a degree by destruction of wild fauna, muzzling, restraint of all cats and dogs and keeping farm animals indoors.

(2) Vaccination: Especially Mass immunization of dogs by campaigns and by continuing vaccination of young dogs in particular, as well as vaccination of all cats and dogs is in general are the important one.

Where the risk of rabies is great consideration must be given to mass vaccination of wildlife by baits, because wildlife is the cracks in the defence armour. The use of combined vaccine containing rabies vaccine with a lot of other vaccines used in dogs would be an effective panic-free way of increasing the immune status of the pet population.

No parenteral vaccine is licensed for wildlife; however, use in captive or free-ranging species has occurred on a case-by-case basis for prophylaxis in zoos or to augment control in the field, respectively. Protective immunity and efficacy from the commer- cially available vaccines for domestic species have not been definitively demonstrated in all wildlife species.

Historically, the control of rabies in wildlife populations relied on population reduction to decrease the contact rate between susceptible animals; however, this proved difficult and often not publicly acceptable, ecologically sound, economically warranted, or programmatically effective.

Concluded...