Rabies is one of the most important zoonotic diseases causing agonizing deaths to the mankind since 4000 years ago. The disease has one of the highest case fatality rate with probably zero recovery rates. Rabies virus belongs to the family Rhabdoviridae wherein the most common source of human rabies is the affected canine population.
The estimated human deaths due to rabies are over 59,000 in 150 countries out of which 95% cases are reported from Asia and Africa. As per World Health Organisation (WHO), in Asia the estimated death is 35,172 human deaths per year and India accounts for 59.9% of rabies deaths in Asia and an estimate of 35% of deaths globally. Due to under reporting, it is obviously an underestimate of the actual burden of disease. Dog mediated rabies cases are of 99% and the prevalence of disease is disproportionally seen in rural poor populations. Unfortunately, more than half of these cases are reported in children who are less than 15 years of age.
The disease is prevalent in all continents except Antarctica and is considered as a Neglected Tropical Disease (NTD) by the WHO. As per World Organisation for Animal Health (OIE), three solutions have been mandated for control and prevention of human rabies. This includes mass vaccination of dogs in infected areas, vaccination for humans and administration of anti-rabies serum post bite by rabies suspected dog.
Control of canine rabies
For the control of rabies, it is ideal to conduct a mass vaccination campaign in the canine population with vaccination coverage of 70 per cent or more. In endemic areas the entire domesticated animals within the locality must be immunised. Pre-exposure prophylaxis aids in protecting vaccinated animals from exposure as well as when exposed towards the next time of vaccination, the post bite vaccination would aid in inducing a protective titre faster in previously vaccinated animals than non-vaccinated animals in which it would take more than two weeks.
In areas wherein dogs are regularly immunized, the maternal antibodies to rabies would be present in milk until 90 days of age. Hence puppies have to be vaccinated at 90 days of age, followed by a booster 2-3 weeks later. In areas, wherein there is high incidence of rabies and in case of non-immunized dams, puppies can be vaccinated at an earlier age. It is important to keep in mind that prior to vaccination the animal must be healthy, and free from all endo and ecto-parasites to acquire the protective titre which is desired.
Dog Population Management (DPM) is another strategy to eliminate rabies by controlling the association between humans and dogs. The different methods that can be used include chemical or immunological sterilization or contraception, surgical sterilization, confinement during oestrus etc. Rabies control programmes should essentially include education and awareness programmes, responsible ownership of pets, surveillance programmes and political support.
Prevention in humans
Categories of contact and recommended post-exposure prophylaxis (PEP) (as per WHO)
Categories of contact with a suspect rabid animal:
Category I: touching or feeding animals, animal licks on intact skin (no exposure)
Category II: nibbling of uncovered skin, minor scratches or abrasions without bleeding (exposure)
Category III: single or multiple transdermal bites or scratches, contamination of mucous membrane or broken skin with saliva from animal licks, exposures due to direct contact with bats (severe exposure)
Post-exposure prophylaxis measures:
» Washing of exposed skin surfaces, no PEP
» Wound washing and immediate vaccination
» Wound washing, immediate vaccination and administration of rabies immunoglobulin
These first-aid measures are immediate and thorough flushing and washing of wound for a minimum of 15 minutes in running tap water with the use of soap and water, detergent, povidone iodine or other agents that could remove and kill the rabies virus. The post-bite vaccination schedule known as PEP includes exposed individuals getting vaccinated on days 0, 3, 7, 14 and 28. Those individuals who have been vaccinated previously need not take the whole course and need to only take dose on day 0 and 3.
Current data suggest that particularly in developing countries more than 95 per cent of human rabies cases are due to dog bites. It is possible to attain the goal of zero rabies by 2030 by progressive control and eventual elimination of rabies. A conjunction of parenteral vaccination and population management of stray dogs can successfully prevent rabies. In endemic areas like India, individuals are still unaware of the risk and measures for the prevention of rabies. Rabies is a vaccine-preventable disease; hence authorities should make the control and prevention of canine rabies a public health priority to prevent human rabies and deaths.
(Dr Anugraha Mercy Easaw is MVSc Scholar and Dr K. Vijayakumar is Professor Head at Department of Veterinary Epidemiology and Preventive Medicine, College of Veterinary and Animal Sciences, Mannuthy, Thrissur)