ZOONOTIC DISEASES-AN EMERGING THREAT

ZOONOTIC DISEASES-AN EMERGING THREAT
Dr.T.P.Sethumadhavan


There are several challenges and persisting problems concerning animal husbandry in the new millenium. They include containment of emerging diseases and prevailing zoonotic infection, better under standing of the diseases of domestic animal species. Global human and animal health scenario in the 20th century witnessed a phenomenal change. Advent of vaccine and effective drugs helped in eradication and control of several dreaded diseases of man and animals. For example, small pox was stamped out globally and Rinderpest, FMD and Rabies were eradicated from several parts of the world. However emergence of number of new health hazards such as AIDS, BSE, pollution disasters to name a few, has caused much concern to human and animal health. The main factors which have contributed to emergence of infectious agents include, human demographics and behavior, technology and industry, economic development and land use, international travel, commerce, microbial adaptation and change in break down of public health measures. Introduction of susceptible exotic animal breeds and import of infected animals or infected animal products, feeds and biologicals also contribute to the emergence of infectious animal diseases. Owing to the higher susceptibility of indigenous breeds to exotic diseases and lack of full proof control measures, emerging diseases spell devastating effects on animal sector.
Bovine spongiform encephalopathy or the mad cow disease was recognized in UK in 1986 for the first time in the world. It caused devastating impact on cattle industry-forcing slaughter of around two lakh cows. It is believed that the new variant CJD, the human form of BSE, had possible link to BSE epidemic in UK and had occurred due to consumption of meat and meat products from affected animals. Besides emerging animal health challenges effective management and control of several prevailing diseases such as Rabies, Tuberculosis, John’s disease, Brucellosis, Mastitis, Leptospirosis, FMD, Salmonellosis, Botulism, Plague, Streptococcosis and Anthrax require marked importance. Ravages of rabies still claim thousands of human and animal life in the Indian subcontinent. Globally out of 35000 human deaths occurring annually due to rabies, more than 85% is from India. These concerns together with prevention and control of widely prevalent parasitic disease which include Toxoplasmosis, Toxocariasis, Dirofilariasis, Hydatidosis, Cysticercosis and other worm infestations.

Leptospirosis is one of the zoonotic diseases with worldwide distribution. With the onset of monsoon it is emerging as a major health threat in the state. Rapid urbanization with poor sanitation, lack of awareness among the public and the professionals has contributed to the disease. Till recently the disease was either neglected or un-reported due to lack of awareness and non-availability of reliable diagnostic tests. Veterinary research priorities in leptospirosis gains most importance by the fact that domestic animals, wild life and rodents are predominant leptospira reservoir hosts directly or indirectly responsible for human infections. There is reason to believe that leptospirosis could be the cause of still births and abortion in animals particularly in cattle and definitely one among the important contributory factors of bovine mastitis. Even dogs and cats are acting as carriers of infection. Epidemiological investigations on natural reservoir hosts with special reference to rodents should be carried out. Veterinarians can play a key role in the diagnosis of leptospirosis. In suspected cases, clinical manifestation in animals’ need to be subjected to detailed serological tests to investigate the disease.
Domestic animals, wild animals and rodents are directly or indirectly responsible for human infection. As part of the research, epidemiological investigations on natural hosts with special emphasis to rodent population should be done. Recognition of location or host specific leptospira serovars, detailed study of clinical manifestations in animals, isolation of the organisms, analysis of relational modules between human and animal leptospirosis and seasonal forecasting of the disease should be carried out. Polymerase chain reaction (PCR), ELISA, Random amplified polymorphic DNA fingerprinting (RAPD) and Arbitrarily primed PCR (AP-PCR) assay are helpful in quick and precise diagnosis.
For eradicating leptospirosis from the state, a multi disciplinary approach is needed. Department of Health services, Animal husbandry and Agriculture departments should work together in an integrated manner to control the disease. As in the case of dogs, in human beings immunization against leptospirosis should be carried out in the endemic areas. During outbreaks chemoprophylaxis should be followed. An efficient and cost-effective rat control measures should be used. Proper disposal of garbage, employment of better sanitary measures coupled with proper awareness programme will help in controlling the disease.
Public, farmers, school children, animal attendants and veterinarians in particular are prone to health hazards of animal origin. There is a special need of creating awareness among public on the world zoonosis day.