Abstract
Bovine tuberculosis is a chronic bacterial disease caused by Mycobacterium bovis. It can be transmitted to humans through direct contact with infected cattle or consumption of unpasteurized milk and milk products. The current study was performed to assess whether raw milk produced in three large scale dairy farms in Central Province of Sri Lanka contain any M. bovis. Raw milk samples were collected from 330 cows representing 230 single intradermal comparative cervical tuberculin test reactors and 100 none-reactors. All milk samples were cultured on Lowenstein Jensen medium with/ without sodium pyruvate for the isolation of Mycobacterium spp., and slopes were observed for the occurrence of growth daily for the first week and then at weekly intervals for 8 weeks. Direct Polymerase Chain Reaction (PCR) was performed simultaneously on all milk samples to detect M. bovis after extracting DNA with a commercial kit. The minimum detection level of M. bovis for PCR in milk was 200 CFU/mL. Only two milk samples from reactive cows were positive for acid fast bacilli. However, their cultures were confirmed as non-tuberculous mycobacteria by PCR. Consequently, all milk samples were confirmed negative for M. bovis according to direct PCR. It was concluded that the milk samples from three large scale dairy farms in Central Province of Sri Lanka did not contain M. bovis.
Highlights
Bovine tuberculosis is an emerging zoonotic disease caused by M. bovis, a member of the Mycobacterium tuberculosis complex (Van Soolingen et al, 1997)
Mycobacterium tuberculosis act as the causative organism in majority of the human tuberculosis cases, a considerable number of cases have been caused by M. bovis in humans (De la RuaDomenech, 2006)
The objective of the current study was to assess raw milk produced in three large scale dairy farms in Central Province of Sri Lanka for the presence of M. bovis using both conventional culture methods and Polymerase Chain Reaction (PCR)
Summary
Bovine tuberculosis is an emerging zoonotic disease caused by M. bovis, a member of the Mycobacterium tuberculosis complex (Van Soolingen et al, 1997). Most mammals are susceptible to M. bovis due to its broad host spectrum whereas, cattle are the primary host among the domesticated animals (Schmitt et al, 2002). Mycobacterium tuberculosis act as the causative organism in majority of the human tuberculosis cases, a considerable number of cases have been caused by M. bovis in humans (De la RuaDomenech, 2006). Mycobacterium bovis in milk control programs and consumption of raw milk or unpasteurized dairy products (Ashford et al, 2001). Bovine tuberculosis can be transmitted to human through inhalation of aerosols, consumption of contaminated food such as milk and meat products or direct contact with infected animals (Une and Mori, 2007). Consumption of unpasteurized milk and dairy products, especially soft and hard cheeses has been identified as the primary risk factor of M. bovis infection in humans (Bolaños et al, 2017)
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