Emergence of clinically suspected listeriosis in goats: a sporadic outbreak in Jaffna district, Sri Lanka

Abstract

Listeriosis is an infectious disease affecting ruminants and a serious foodborne illness in humans. Index cases with neurological signs suspected of Listeriosis were reported from ten Veterinary ranges of Jaffna District in August 2021. Field investigation with 937 animals from 262 farms revealed the characteristic clinical manifestations of the disease. The brain samples of dead animals were subjected to microbiological and histopathological analysis and confirmed as Listeriosis. Antibiotic sensitivity test was performed using disc diffusion method and amoxicillin, tetracycline, enrofloxacin and trimethoprim/ sulfamethoxazole were found to be sensitive to the isolates of suspected Listeria monocytogenes.The outbreak affected the goats regardless of breed and sex with a high incidence in goats of 1-3 years of age. Encephalitic form of Listeriosis was primarily observed with a high case fatality rate (77.8%). The mortality rate was high (84%) in adult goats and a low recovery rate (22.22%) was recorded in the overall population despite the routine therapeutic interventions. However, preventive measures adapted to control the outbreak within and outside the district were a success. This is the first report of the emergence of a Listeriosis outbreak in Jaffna District and it highlights the need to initiate preventive strategies for the future occurrence of Listeriosis as it is a possible threat to public health.