Tuberculosis in apparently healthy milch cows

Area of Science:

• Veterinary Microbiology
• Bovine Tuberculosis Research
• Food Safety

Background:

• Bovine tuberculosis (TB) poses a significant threat to animal health and public safety.
• Early detection of Mycobacterium bovis in dairy cattle is crucial for effective disease control.
• Subclinical infections in apparently healthy animals can contribute to disease transmission.

Purpose of the Study:

• To screen apparently healthy milch cows for the presence of mycobacteria.
• To investigate mycobacterial shedding in milk and presence in supramammary lymph nodes (SLNS) and udder tissue.
• To assess the prevalence of tubercle bacilli in milk from cows suspected of tuberculous mastitis.

Main Methods:

• Samples of milk, SLNS, and udder tissue were collected from apparently healthy and suspected tuberculous milch cows.
• Mycobacterial screening was performed on all collected samples.
• Prevalence rates were calculated for different sample types and animal health statuses.

Main Results:

• Tubercle bacilli were detected in 5% of milk samples from apparently healthy slaughtered cows and 7% from live cows.
• Milk from cows suspected of tuberculous mastitis yielded 8% (slaughtered) and 10% (live) positive results.
• Mycobacteria were isolated from SLNS irrespective of visible lesions, and udder tissue tested positive even without apparent lesions.

Conclusions:

• Mycobacteria can be present in the milk, SLNS, and udder tissue of apparently healthy dairy cows.
• Subclinical mycobacterial infections are detectable and may be more prevalent than indicated by visible lesions.
• These findings underscore the importance of comprehensive screening protocols for bovine tuberculosis in dairy herds.