Brucellosis in Cattle

Although most states are now brucella-free, brucellosis still causes abortion and infertility in some regions. It is important to understand that not all brucellosis-infected cows abort, produce weak calves, retain placenta or have trouble breeding back. A brucellosis reactor cow may be normal in every observable aspect. However, each time she calves or produces a genital discharge, millions of brucella organisms may be present on the surface of the placenta, calf or discharge. The discharges then contaminate the pasture and other feeds, such as hay, threatening other cattle. If susceptible animals ingest these bacteria, they are likely to become infected.

Although infection usually occurs via the digestive tract, a susceptible animal may also pick up bacteria through the skin or eye. Contaminated feed, bedding, water or the premises may remain infective for a few days up to a few weeks, depending on environmental conditions.

The infection is spread mainly when infected cattle are introduced into the herd, either through purchase or when they break into a pasture with “clean” cattle. To keep your herd “Bang’s free,” maintain a closed herd by raising all your own replacements if possible. If you must buy replacement cattle, know the seller’s reputation. Be sure that all cattle you buy originate from clean herds, and that the females were vaccinated as calves and are negative to the Bang’s test if they are of testable age.

Isolate breeding stock for 30 to 60 days upon arrival at the farm and retest at the end of the isolation period. A lot of trouble? Yes, but not if a lifetime’s effort is risked in building a quality herd. At the same time, test the new animals for other reproductive diseases as recommended by the local veterinarian.

It is recommended to have an accredited veterinarian vaccinate all heifers between 4 and 12 months old. The calves should be properly identified, with an official ear tag and tattoo in the right ear.

Be sure that bulls are free of brucellosis and all reproductive diseases. Although brucellosis is rarely spread through breeding, it is still dangerous for a bull to breed an infected cow and then breed a clean cow soon thereafter. Bulls occasionally become infected; this is usually exhibited by a swollen testicle or scrotum. Producers using artificial insemination should avoid semen from brucellosis infected bulls. Their semen can infect cows.

Source:

Reproductive Diseases in Cattle

EDITED BY L. R. SPROTT AND ROBERT W. FIELD