The unexpected nature of the occurrence of such diseases, which are transmitted between animals and humans, makes it even more challenging. Scientists claim that emerging infections usually prove more threatening because there is little information on their origin and many of their epidemiological features remain unknown.
Major public health zoonotic diseases in India include Rabies, Brucellosis, Toxoplasmosis, Cysticercosis, Echinococcosis, Japanese Encephalitis (JE), Plague, Leptospirosis, Scrub typus, Nipah, Trypanosomiasis, Kyasanur forest disease (KFD) and Crimean-Congo haemorrhagic fever (CCHF).
According to the National Centre for Disease Control (NCDC), about 75% of emerging and re-emerging infections are zoonotic, and new pathogens (viruses) continue to emerge and spread across countries.
“An updated literature survey indicated that 816 of the 1,407 (58%) human pathogens, included viruses (208), bacteria (538), fungi (317), protozoa (57) and helminths (287), were zoonotic that are capable of being transmitted naturally between animals and humans. Of these 37%, 10%, 7%, 25% and 10 3% were emerging or re-emerging," said Rajeev Kumar a veterinary public health and epidemiology expert.
Controlling and preventing zoonotic diseases in a country like India is challenging because of a huge human population and its frequent interactions with animals. Poverty-struck communities are primarily dependent on rearing animals as a means of livelihood and, therefore, the intimate human-animal contact puts them at risk for this category of diseases.
Scientists have called for developing a modern disease surveillance system using new approaches and tools such as syndromic surveillance, geographic information system, remote sensing, molecular epidemiology, information technology, bioinformatics, economics and sociology.
“We need to develop a close network between veterinary and medical laboratories and professionals at different levels. The professionals must become part of rapid response teams to investigate epidemics of zoonoses," said S.P. Singh, professor and head, department of veterinary public health and epidemiology, G.B. Pant University of Agriculture and Technology, Pantnagar.
“Each district and state in the country needs to be linked through satellite to the designated national headquarters for collecting real-time data on the activity of pathogens and diseases. Our performance in this regard has not been too encouraging," Singh added.
The classic example of emergence of zoonotic disease is the outbreak of Nipah in Kerala. The virus can be transmitted to humans from animals (bats and pigs), and can also be transmitted directly from human-to-human. Fruit bats of the Pteropodidae family are the natural host of Nipah virus. India had reported two outbreaks of Nipah virus encephalitis in West Bengal, bordering Bangladesh, in 2001 and 2007.
“In India, lack of proper vaccination programmes, poor sero-surveillance and lack of diagnostic facilities make the preventive and precautionary approach more difficult. We should have been watchful in case of Nipah as there was an outbreak a decade ago. Wild infections, such as Nipah, can travel across geographies and it is important to monitor what is happening in the neighbourhood," said Avinash Srivastava, a Delhi-based veterinarian.
“As of now, India does not have a proper policy for these emerging challenges. Endemic areas should be ear marked and regular monitoring should be done for zoonotic diseases," he added.
Considering the situation of zoonotic diseases, the government has decided to form a national task force comprising medical, veterinary and environmental experts, and plans to make veterinary public health a part of the national health mission.
The government also plans to study the economic impact of zoonotic disease outbreaks in humans so that prevention and control guidelines are framed well in advance by both medical and veterinary fraternities.
“For effective prevention and control of zoonotic diseases there is a requirement of multi-sectoral integrated response among medical, veterinary and other related departments. This has been adopted on a “need basis" for preventing zoonosis in the country. Under the 12th plan, a programme for strengthening mechanism of inter-sectoral coordination for prevention and control of zoonotic diseases has been approved and is being implemented," said A.C. Dhariwal, advisor, National Vector Borne Disease Control Programme.