Human Rabies Deadly but preventable
View(s):Rabies is an invariably fatal disease with 100% mortality. The causative agent is a rhabdovirus which is bullet shaped and found in suspected animals which could be transmitted to other animals or humans through bites, scratches, licks on open wounds or mucous membranes. The virus is inactivated by detergents, alcohol or tincture iodine.
A dog being vaccinated by a vet from the Blue Paw Trust. File pic
Dogs are the main reservoir for rabies in Sri Lanka. But there’s good news! In the early 90’s there were 100-150 human rabies deaths reported, but in 2013 the reported deaths have been brought down to 27, an achievement for Sri Lanka.
Clinical disease
The incubation period (IP) in rabies is variable. It can vary from less than one week to more than one year. However, in most cases it falls between one to three months. The incubation period is found to be shorter when the bites are on the face or head than when they are on the lower extremities. Children often have a shorter incubation period than adults, possibly because they often get bitten on the face, head and neck which are classified as severe exposures.
Clinical rabies is of 2 types:-
Furious type- hyperactivity predominates. Seen in about 80% of patients
Paralytic or dumb type- paralysis predominates. Seen in about 20% of patients
Onset of clinical illness is insidious with malaise, fatigue and fever. The patient may complain of pain, weakness or paralysis of the bitten limb even though the wound has already healed. As the disease progresses, agitation, photophobia, nightmares or other bizarre behaviour are seen. 17-80% of patients exhibit the characteristic sign of rabies, namely “hydrophobia” which means fear of water. Both types eventually progress to complete paralysis followed by coma and death due to respiratory failure within 10-14 days of developing symptoms.
Rabies diagnosis
The Medical Research Institute (MRI) is the National Reference Laboratory for rabies diagnosis in Sri Lanka. Two regional decentralized laboratories have been established at the Teaching Hospital Karapitiya in the Southern Province and at the Faculty of Veterinary Science, University of Peradeniya in the Central Province.
In Sri Lanka, the following animals have been proved positive for rabies by laboratory diagnosis:- dogs, cats, cows, goats, mongoose, pole cats, bandicoots, monkeys, horses, rock squirrels, jackals, civet cats and elephants. So far, house rats have not been proven positive for rabies in Sri Lanka. The MRI is open 24 hours to accept suspected specimens. It should be noted that only the suspected animal’s head within 6-8 hours of death is accepted for diagnostic purposes. One should take precautionary measures like wearing gloves when severing the head of the rabies suspected animal. The specimen should be sent in a leak proof container. If more than eight hours is taken in transporting the specimen, it should be packed in ice to prevent decomposition.
The following information should be submitted at the time of handing over the specimen to the laboratory:- type of animal, domestic , stray or wild animal, name of owner/sender , contact telephone number and address of owner/sender, colour or any identifying marks on the animal, vaccination status of the animal and whether died or killed.
Anti rabies post exposure vaccination
The term exposure refers to a contact with rabies virus which has a potential to cause disease. This could be either a bite or a scratch by a suspected rabid animal or the contamination of an open wound or mucous membranes with saliva or infected tissue from an infected animal or human. The risk of rabies after a bite by a rabid animal is very much higher than the risk due to scratches.
The most important first aid procedure to be adopted to reduce the viral load at the site of the bite, is to wash and flush the wound thoroughly, with soap and water, detergent followed by the application of alcohol, surgical spirits or tincture iodine. Where indicated, anti tetanus immunisation and antibiotics should be administered to control bacterial infections. Patients should seek medical advice from the nearest hospital with regard to anti rabies vaccine therapy.
During the past two decades, considerable progress has been made in the production and use of more effective and safer rabies vaccines. At present, only anti rabies vaccine of cell culture origin which is administered on the upper arm is used in Sri Lanka and is given free of charge through government hospitals.
It is very important that a person who has been exposed to the rabies virus is administered post-exposure therapy as soon as possible. This is to destroy the virus before it gains entry to the nervous system. If the animal involved is a pet, its immunization records should be submitted to the health care staff in the hospital. Type of treatment will be decided by the medical officer, depending on several factors (i.e. site, severity of the injury, health status, immunization history of the animal and whether animal is observable or not).
For high risk exposures, rabies immunoglobulin should also be administered before vaccine therapy. This is given to all the wounds to destroy the virus and any remaining volume is given to the thighs. For low risk exposures, only the vaccine is recommended. The anti rabies vaccine consists of 4 to 5 injections given within a month, depending on the schedule used. One should keep in mind that it is important that the vaccine is taken on specific dates given by the hospital authorities to develop maximum protection against rabies. If instructions are followed correctly, one should not worry about getting the disease even if the animal concerned was proven rabid by laboratory diagnosis. The patient’s immunization records should be kept safely and submitted to the medical officer if re-exposed.
Rabies animal control
For effective control of rabies in Sri Lanka, the following strategies should be adopted.
Regular anti rabies vaccination of dogs, cats and other domestic pets annually.
Puppies and kittens should be given the first rabies vaccine at the age of six weeks and again given a booster vaccine at three months and thereafter every year
Responsible pet ownership- registration and vaccination of dogs, restraining the animal within the owner’s premises either by caging or leashing to protect the community
Sterilisation of female dogs and cats to reduce the population and unwanted litters.
Improve environmental sanitation by proper garbage disposal
Control of stray dogs
By adopting strict control measures and better community participation, Sri Lanka being an island, we should be able to eliminate rabies hopefully by 2020.
(The writer is a Consultant Vaccinologist and Medical Virologist)