PCR investigation of the vertical transmission of Mycobacterium bovis in Montbéliarde cattle in Gonbad, northeast of Iran

Bovine tuberculosis is an important global zoonosis. The causative agent of the disease is Mycobacterium bovis, belonging to the Mycobacterium tuberculosis complex. This study aimed to identify vertical transmission of Mycobacterium bovis in tuberculin positive pregnant dairy cows referred to the slaughterhouse and commercial sperm used to inseminate them in Gonbad, Gorgan province, Iran, by PCR assay. From March to September 2016, one thousand and seven hundred artificially inseminated cows were subjected to the tuberculin test; then, tuberculin positive cows were referred to the Gonbad slaughterhouse. Samples containing milk, lymph node, placenta, foetal abomasal fluid, and amniotic fluid were prepared from all affected cows and stored at -80 °C until analysis. Bacterial DNA was extracted from all specimens by a commercial kit. Detection was performed by amplifying pncATB gene using special primers via the polymerase chain reaction method. Results of tuberculin test revealed 144 positive cases (8.47%). PCR results for 48 milk samples, 120 biopsy samples, 63 samples of foetuses showed 9, 93 and 43 positive cases, respectively which all belonged to tuberculin positive samples. No positive sperm samples were identified. It was concluded that the infection rate with M. bovis in Montbéliarde cattle was high and also, that vertical transmission was not seen.