Detection of Mycobacterium bovis in cattle lungs from two abattoirs in Western and North Central provinces of Sri Lanka

Mycobacterium bovis causes bovine tuberculosis (BTB) primarily in cattle. All mammals are susceptible to this zoonotic disease and it had been reported from the Central and North Western provinces of Sri Lanka.  Abattoir monitoring is usually used for BTB surveillance in endemic countries. However, a proper ante-mortem inspection of cattle and proper meat inspection is practised only at a few abattoirs in Sri Lanka. The objective of this study was to conduct a preliminary assessment of BTB incidence among cattle used for beef production at two abattoirs in Western (WP) and North Central (NCP) provinces in Sri Lanka. Randomly collected 115 lung samples (WP = 45; NCP = 70) were tested using direct acid-fast staining, culture on Lowenstein Jensen medium, histopathology and PCR. Mycobacterium tuberculosis complex was detected in 7.0 % of the samples by PCR conducted using DNA extracted directly from samples. Only 5.2 % of the samples (4.45 % from WP and 5.7 % from NCP) were positive for M. bovis specific PCR.  Only one (0.87 %) PCR positive sample from NCP had a granuloma on histopathological observation, suggesting a relatively low incidence of BTB among the cattle processed at these abattoirs. Mycobacterium bovis isolates were not recovered and acid-fast bacilli were not observed in direct smears. Initiating proper meat inspection at all abattoirs in the country along with increased BTB surveillance capacity of the national veterinary service is required to mitigate this risk. Further studies are essential to determine the exact prevalence of BTB in Sri Lanka and to identify any wildlife reservoirs of BTB in the country.