Unmasking a viral disease with 100% fatality rate

CHENNAI: Rabies-related human fatality remains a non-notifiable disease in the country, but with at least 25-30 deaths almost every year in TN, it’s certainly a major health concern.

Rabies, a viral zoonotic disease, is usually fatal in nature and is caused by the Rabies virus, passed from animals to humans with a bite and often, from dogs.

A research paper on ‘Rabies as a Public Health Concern in India – A Historical Perspective’ published in the National Library of Medicine, states, “Human and animal rabies was widespread in British India, and treatment of victims imposed a major financial burden on the colonial GoI. It subsequently became a driver of pasteurism in India and globally, and a key component of British colonial scientific enterprise. Efforts to combat rabies led to the establishment of a wide network of research institutes in India and important breakthroughs in the development of rabies vaccines. As a result, rabies no longer posed a significant threat to the British, and it declined in administrative and public health priorities in India towards the end of colonial rule — a decline that has yet to be reversed in modern-day India.”

Deaths globally

There are around 59,000 rabies-related human fatalities each year globally as per a World Health Organisation report from 2018. India accounts for about 35% of all cases (around 20,000 deaths/year).

Most cases are caused by dog bites and a majority are reported in rural areas, as they have limited access to diagnostic facilities and post-exposure prophylaxis. Dog owners were also charged with a penalty if a rabid dog bites another person.

With population explosion over the years across the country and undiagnosed viral infections, many human-rabies deaths go undetected and under-reported. There is a need to ensure the availability of safe and effective vaccines, awareness of and access to post-exposure prophylaxis (PEP), including rabies immunoglobulin.

Incubation period

Dr S Chandrashekhar, HoD-General Medicine, Stanley Medical College, explains that the incubation period of the virus is around three months in humans usually. It can be present in the body even after several years and depends on the bite.

The head and neck bite have a shorter incubation period due to the proximity to the brain. In a severe case of the disease, the patient must be treated immediately.

“Early symptoms can range from muscle pain, unpleasant sensations at the site of the bite, dizziness, fatigue, fever, loss of appetite, fear, nausea and sensitivity to light in over 1-10 weeks. There can be fear of air ventilation and drinking water as the disease progresses. There is agitation, disorientation and it’s most likely to be fatal,” he said. “In dogs, 20% of the rabies cases show dullness, drooling of saliva, but the aggressive form is very common.”

Incubation period in dogs is between 2 weeks and 4 months. A rabid animal can present with non-specific symptoms initially. “Other symptoms include lethargy, fever, vomiting, and slowly it can progress to ataxia, weakness, difficulty in breathing and swallowing food, paralysis, fear of water, and seizures,” he explained.

Immediate care after a dog bite includes washing the wound area with carbolic soaps, and seeking medical care from a qualified doctor. Any delay will prove detrimental, and often fatal.

Dr P Dhanapalan, a veterinarian, adds: “As the virus moves to the central nervous system, progressive and fatal inflammation of the brain and spinal cord develops. As neurological complications develop, symptoms will become worse.”

Also, secure the animal that bit the person and take it to a designated ‘under observation for rabies’ facility in nearby veterinary institutions to test for rabies.

In dogs, wild animals

Rabies only transmits from an infected animal and when coming to stray dogs, one cannot determine if a dog is infected. Though the furious form of rabies is commonly known to the public, there are 3 types and stages of rabies in dogs — dumb, aggressive and paralytic rabies.

Within the first 2-3 days of the infection, the dog shows signs of restlessness and progresses to anxiety and aggression. “When a dog presents with dumb rabies, it doesn’t show the typical furious behaviour. It becomes lethargic and shows very low physical activity. In Royapuram, the dog showed such behaviour and it bit 29 people in an hour,” said R Sokkalingam, a senior veterinarian. “A rabid dog will not stay in one place and will be very restless. The bite can be unprovoked. It will just keep running and upon human intervention, it can bite them. If a stray dog bites a pet dog, a veterinarian needs to be consulted and vaccination is mandatory.”

He added that when the dog presents with the dumb form of the disease, it cannot be diagnosed immediately. “The dog needs to be isolated and its behaviour should be monitored for at least 10 days. It’s easier to determine the signs when the dog has an aggressive form of rabies. The paralytic rabies, which usually occurs in the end stage, takes longer than the furious form,” stated Sokkalingam.

Rabies cases among wild animals have decreased drastically and has become the rarest incident in the State. Earlier, dogs were fed leopards which had transmitted the infection to other carnivores.

Dr K Sridhar, a wildlife veterinarian, explained, “Dogs living around forest areas have been vaccinated so the rabies infection among the wildlife animals is under control. There are no cases of rabies in wild animals in TN. Though the virus can spread to all mammals, the spread from dogs to other animals is high due to their aggressive behaviour towards other animals. Since the population is less in the forest, the spread of infection is also less.”

The incubation period among rabies-infected wildlife is between 3 days and 6 months. If an animal dies in the forest because of rabies, it would be incinerated.

“If residents maintain a pet dog in their house there won’t be any issue, until it has been abandoned near a forest area. Dog owners and animal activists should prevent such incidents,” added Sridhar.

The incidents of rabies in wild animals including spotted deer, elephants and rhinos in the zoo has been documented. But there is no research to identify the number of cases in the forest in TN. “The State government should give approval and allocate funds to conduct research regarding the spread of rabies infection in wild animals in the forest, as the State does not have any proper data,” said Dr Jayathangaraj, Centurion Veterinary College, Odisha.