Rabies: fatal but preventable

by Carol Aloysius

World Rabies Day observed on September 28 drove home some hard facts about this disease which is still shrouded by myths and continues to remain a threat to thousands of Sri Lankans who are constantly exposed to the danger of being bitten by rabid dogs.

Director Rabies Control Unit Dr P.A.L. Harischandra tells the Sunday Observer how this remarkable turnaround was achieved, while discussing symptoms of the disease and how to prevent it.

Excerpts...

Q: Rabies is one of the most widely prevalent diseases worldwide. Yet many people constantly exposed to its danger misunderstand it. What is Rabies?

A: Rabies is a disease caused by a virus belonging to the rhabdovirus group. Rabies can infect animals as well as humans. Animal rabies can occur among a wide range of warm blooded animals both domestic and wild dogs, cats, cows, giant squirrels, bandicoots, mongoose etc. Humans get the disease from animals. Hence it is a zoonotic disease, which means that an animal who has the disease can pass it on to humans. Rabies is present on all continents in the world with the exception of Australia. However over 95% of deaths occur in Asia and Africa. 95% of human rabies occurs due to infected dogs. 59,000 human rabies deaths occur world-wide annually.

Dogs are the main host and transmitter of rabies. With the number of human rabies deaths peaking to nearly 400 in the early seventies in Sri Lanka human rabies was made notifiable since1972.

Q: Is there a difference between human rabies and animal rabies?

A. There is no difference in terms of fatality as both humans and animals will die once symptoms develop. However Rabies though a 100% deadly disease, is also100% vaccine preventable.

Q: What are the signs and symptoms of the disease in dogs and humans? Are they very different?

A. The signs and symptoms are also very much similar with change of behavior, agitation, drooling and paralysis. 75% of dog rabies are paralytic and only 25% is furious. On the other hand 75% of human rabies is furious.

Q: How do they transmit the disease to humans?

A. Transmission of Rabies is commonly through infected saliva of an infected animal entering the body of another animal or human via bites, scratches or licks on broken skin and mucous membranes. The rabies virus which is present in the saliva will enter the wound site, once it reaches the nervous tissue it attacks the central nervous system giving rise to the symptoms and signs of encephalitis.

Q: How long does it take for symptoms to present?

A. The time between the exposure occurrence and the signs of rabies is called the incubation period.

The incubation period is typically 1-3 months, but may vary from below 1 week to over 1 year. The incubation period depends on factors such as location of rabies entry (eg. Site of bite) and rabies viral load that entered the wound. The initial symptoms of rabies are fever and often pain or an unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site. As the virus spreads through the central nervous system, progressive, fatal inflammation of the brain and spinal cord develops.

Q: You mentioned that Rabies can manifest itself in two forms in humans , namely, furious and paralytic ( dumb) rabies , depending on which symptoms develop in an infected person. What are these symptoms and how can one identify them?

A. Furious rabies is the commonest form, exhibiting signs of hyperactivity, excited behaviour, hydrophobia (fear of water) and sometimes aerophobia (difficulty in breathing). After a few days, death occurs by cardio respiratory arrest. Paralytic rabies occurs in about 30% of the total number of human cases. This form of rabies has a less agitated and usually longer course than the furious form. The muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops, and eventually death occurs.

Q: How is rabies diagnosed? Can one diagnose the disease before its onset?

A. Unfortunately there are no tests available to diagnose rabies infection in humans before the onset of clinical disease.

Q: So how is it diagnosed eventually? After the patient has died? Or while having the symptoms?

A. It can be confirmed post mortem by various diagnostic techniques which detect whole virus, or viral antigens.

Q: Vaccinations against rabies - how effective are they in preventing rabies? Can they cure rabies as well?

A. Rabies vaccines and Immunoglobulin can only prevent rabies if it is given to the victim before the virus reaches the nervous system that is immediately after bite. Vaccination cannot cure rabies once the clinical symptoms appear in the victim. Vaccinating dogs is the most cost-effective strategy for preventing rabies in people.

Q: Why?

A. Dog vaccination will reduce not only the deaths due to rabies but also the need for Post Exposure Prophylaxis as a part of dog bite patient care. This is a key benefit as the government at present spends around four hundred million rupees annually for animal bite treatments.

Q: What about preventive immunization in humans? When do you recommend it and who are your target groups?

A. Pre-exposure immunization is recommended for people in certain high-risk occupations such as laboratory workers dealing with live rabies and other rabies-related viruses, and people involved in any activities that might bring them into direct contact with bats, carnivores, and other mammals in rabies-affected areas.

Q: What about children who constantly play with dogs? Aren't they vulnerable to rabies exposure as well?

A. Yes, children are at higher risk because they tend to play with animals and may thus receive more severe bites from these animals, which they may not report. Therefore children wherever they live must be educated not to play with unknown dogs.

Q: The term Post-exposure prophylaxis (PEP.) is used for rabies treatment. What is it? When is it given?

A. Post-exposure prophylaxis (PEP) treatment is given to a person who has been bitten. Ideally this is started immediately after exposure in order to prevent rabies from entering the central nervous system.

Q: What is the procedure you usually follow?

A. When a patient with bites is admitted local treatment of the wound is initiated as soon as possible after exposure. First -aid of rabies prevention includes immediate and thorough washing of the wound for a minimum of 15 minutes with soap and running water. Thereafter, a course of Anti Rabies Vaccine (ARV) is very important to complete the whole course of vaccinations as recommended by the doctor, otherwise the patient may not be fully protected against rabies. If indicated, Rabies Immunoglobulin (RIG) is also inoculated in the patient.

Q: You have been spearheading innovative rabies control programmes for several years in Sri Lanka. What are the more recent changes in the program?

A. Public Health veterinary services in the Ministry of Health have been spearheading innovative rabies control programers for the past 30 years in Sri Lanka to reach lowest incidence of human rabies in 2016. Dog population control strategy was changed to animal birth control program and adoption of responsible dog ownership.

Since the new changes go beyond the scope of health service, a new strategy was developed to launch joint programs with the Ministry of Rural Development and Ministry of Provincial Council and Local Government.

Q: Under the National Strategic plan to Eliminate Rabies, your goal is to achieve that target by the year 2020. Given the obstacles you still face, is that possible?

A. We have statistics to prove that rabies control measures since 1975 have drastically slashed the number of human rabies deaths. The dedicated involvement of stakeholders to implement new strategy will make rabies elimination feasible and possible.

Q: Examples?

A. The number of human rabies deaths declined from 377 in 1973 to 24 in 2015. As of 20th September the number of deaths are 12 for 2016. Strengthening animal birth control activities and mass rabies vaccination of dogs with the support of stakeholders of Animal health and Local Government sectors, we are confident that rabies elimination can be achieved by 2020

Colombo being one of the most overpopulated cities with its dense population and the presence of large numbers of community dogs roaming the streets, was considered one of the most vulnerable cities at risk to this deadly disease.

In a recent interview, Colombo Municipal Veterinary Unit Chief Dr Vipula Dharmawansa told the Sunday Observer the number of rabies positive dogs had now declined dramatically. He said, "Before the year 2000, there were fifty positive cases of rabid dogs in the city.

The number plunged drastically to a mere three in 2015. As of now the figure stands at zero. This year so far no cases of rabies have been reported. If we can sustain this zero score for the next three years, we can declare Colombo city to be Rabies Free by the year 2018."

(pix from Rabies Control Unit)