Mycobacterium Bovis - Pathogenesis

Pathogenesis

During the first half of the 20th century, M. bovis is estimated to have been responsible for more losses among farm animals than all other infectious diseases combined. Infection occurs if the bacterium is ingested.

M. bovis is usually transmitted to humans via infected milk, although it can also spread via aerosol droplets. Actual infections in humans are rare, mainly because pasteurisation kills any bacteria in infected milk; also, cattle are randomly tested for the disease and immediately culled if infected, but can still be used for human consumption. However, in areas of the developing world where pasteurisation is not routine, M. bovis is a relatively common cause of human tuberculosis.

Bovine TB is a chronic infectious disease which affects a broad range of mammalian hosts, including humans, cattle, deer, llamas, pigs, domestic cats, wild carnivores (fox, coyotes) and omnivores (possums, mustelids and rodents); it rarely affects equids or sheep. The disease can be transmitted in several ways; for example, badgers excrete M. bovis in exhaled air, sputum, urine, faeces and pus, so the disease can be transmitted by direct contact, contact with the excreta of an infected animal, or inhalation of aerosols, depending on the species involved.