Bovine tuberculosis in pigs
What is bovine tuberculosis?
Bovine tuberculosis (bTB) is an infectious disease of cattle. It’s caused by the bacterium Mycobacterium bovis (M. bovis), which can also infect and cause disease in many other mammals, including humans, pigs, deer, goats, cats, dogs and badgers. In pigs, tuberculosis is most often caught during slaughter as clinical signs are rare.
How is it spread?
Pigs are classed as a spill-over host. This means when levels of bTB circulating among wildlife and cattle in the local environment become very high, it spills over into other species, which are not usually infected with bTB.
This situation is most likely to occur in bTB hotspots, such as the South West and the Midlands. However, it is essential that all producers are vigilant due to ‘off-site’ contract growing and finishing, and pigs being moved between regions for finishing.
How do pigs get bTB?
Infected badger urine or mucus is the most likely cause. This can contaminate farrowing beds so that when newborn piglets inhale into the bed or suckle, they become infected.
Another route of contamination includes home mill and mix units using grain from their own or other stores that have been contaminated by bTB-infected badgers. It can also happen through direct contact with other infected animals, e.g. cattle, deer or wild boar. Contaminated crops pre-harvest is not thought to be a likely source of infection.
Why should I be concerned about bTB?
Bovis infection in pigs is a notifiable disease. TB in animals caused by M. bovis is a zoonotic disease and, therefore, where TB in pigs is disclosed, the Animal and Plant Health Agency (APHA) will inform the consultant in communicable disease control (CCDC) of the local health authority, or the relevant consultant in public health medicine (CPHM) in Scotland, so that any risks to human contacts can be investigated.
If TB is confirmed, or if there is a strong suspicion of TB infection in pigs, movement restrictions will be imposed (if not already in place) and will remain until APHA is satisfied there is freedom from TB.
What can I do to prevent bTB?
The key to prevention is to stop infected badgers and cattle from encountering pigs or pig feed.
Many other species can be infected with bTB so it’s important to look at how close other species are to your pigs. This is particularly important in pedigree and small herds, where nose-to-nose contact with other species is more common.
How do I know if bTB is present on my unit?
Pigs rarely show any clinical signs of bTB so infection is usually not discovered until the pigs are slaughtered. UK legislation requires that all animals must be inspected for TB during routine post-mortem meat inspection. If TB lesions are found in the lymph glands of the head, the head will be condemned. If suspect TB lesions are found in more than one part of the carcase site (e.g. head and chest), the whole carcase will be condemned.