The use of PCR technique in the identification of Mycobacterium species responsible for bovine tuberculosis in cattle and buffaloes in Pakistan.

Bovine tuberculosis is one of the important diseases of dairy and wild animals. The disease is prevalent all over the world, though developed countries have tremendously reduced the prevalence through eradication campaigns. The prevalence of disease in Pakistan on the basis of tuberculin testing or culture isolation of the organism has been reported previously. It is, however, important to use the latest diagnostic tools, i.e. PCR to confirm the type of Mycobacterium infecting the animals in Pakistan. Therefore, the present study was carried out to assess the utility of direct PCR on milk samples and nasal swabs to confirm the type of Mycobacterium infecting the animals. This study was carried out on 215 cattle and buffaloes of more than 2 years of age present at two livestock farms. The tuberculin results showed 22.5% prevalence at one farm and 25.9% at the other with an overall prevalence of 24.7%. The 92.5% of milk samples and/or nasal swabs showed positive PCR for Mycobacterium genus, 86.8% for Mycobacterium tuberculosis complex and 77.4% for Mycobacterium bovis. The M. bovis by PCR was detected in 13.2% of milk samples, 24.5% of nasal swabs and 39.6% of both milk samples + nasal swabs. The results suggested that there are 60% higher chance for a nasal swab to yield a positive PCR for M. bovis than the milk sample. It can be concluded from the present study that tuberculin testing is a useful method in studying the prevalence of disease as the PCR for Mycobacterium genus was positive in 92.5%, M. tuberculosis complex in 86.8% and Mycobacterium bovis in 77.4% cases.