Epidemiological and laboratory investigation of a zoonotic anthrax outbreak in West Bengal, India

Objective: To investigate an anthrax outbreak affecting multi-species of animals including human in five remote tribal villages in West Midnapur district, India, with no previous history of anthrax cases for decades. Methods: A systematic epidemiological investigation, along with bacteriological examination, cultural isolation, biochemical and molecular characterization of the samples (blood, dried meat, pieces of bones) was carried out to con firm diagnosis, identify transmission routes and risk factors to recommend suitable control measures. Results: Samples from nine animals were confirmed for presence of Bacillus anthracis by characteristic morphology, biochemical profile, McFadyean reaction in blood smear, ‘medusa head’ appearance of colonies and PCR based detection of pXO1 plasmid. Epidemiological investigation revealed that the human patients contracted the infection during butchering or while handling contaminated animal products. In total, 14 animals died and 11 people got infected with cutaneous anthrax during the outbreak period. Conclusions: Anthrax continues to be a persisting problem in Indian subcontinent causing considerable morbidity and mortality in animals and human. Collaborative efforts of human and animal health officials through various controlled measures viz., ring vaccination, early treatment of human cases, quarantine of affected animals, safe disposal of carcass and public health campaign effectively controlled the zoonotic anthrax outbreak.