Use of molecular methods to detect shedding of mycobacterium bovis in cattle faeces and milk
Sokoine University of Agriculture
Bovine tuberculosis (BTB) is a chronic bacterial disease caused by Mycobacterium bovis. It affects cattle and occasionally other animals and human. Several techniques exist for detection of BTB in animals. In Tanzania, Single Intradermal Comparative Tuberculin Test (SCITT) and abattoir meat inspection are the commonly used methods for screening of BTB. This study has used molecular biology method namely; RD4 Real time PCR (RD4 Rt PCR) to detect shedding M. bovis in milk and faecal samples from cattle tested by SCITT and Bovigam test. The study has also determined the detection limit of Immunomagnetic capture (IMC) and Centrifugation methods of M. bovis cells in spiked milk. A total of 63 cattle dairy form LITA farm Morogoro were tested for BTB with SCITT and Bovigam test. Faecal and milk samples were collected and RD4 Rt PCR was used to detect M. bovis DNA. BTB prevalence detected by SCITT and Bovigam was 3.1% and 3.1% respectively and BTB prevalence detected by RD4 Rt PCR in milk and faeces was 36.1% and 9.5% respectively. The kappa value between the SCITT and Bovigam was 1 and between shedding of M. bovis in milk and faeces detected using RD4 Rt PCR was 0.07. The detection limit of IMC and centrifugation coupled with Real time PCR ranges from 100 to 1 000 M. bovis cells per 500 μl milk and 10 to 100 M. bovis cells per 500 μl milk sample. High number of cattle was detected by Real time PCR to have BTB compared to SCITT or Bovigam. The confirmation of M. bovis in milk indicates potential root of transmission of M. bovis from cow to calf also to human who consume raw milk. Moreover, confirmation of M. bovis in feces indicates possible contamination of cattle carcasses during slaughter process. The study proposes that in order to improve BTB diagnosis for controlling and management of BTB, both conventional, SCITT or Bovigam and molecular methods in feces and milk need to be deployed in parallel but considering their own merits like cost and repeat access to animals.
Molecular methods, Mycobacterium bovis, Cattle faeces, Cattle, Shedding, Shedding detection, Milk