Brucellosis is a zoonotic disease, an infectious disease found in animals transmissible to humans. Brucella is the causative organism of this disease.

The genus Brucella is formed by a variety of species. Each one has a natural host, yet the infection among hosts is frequent. The species Brucella abortus mainly affects bovines. Goats and sheep are a natural host for Brucella melitensis.

Infected animals cannot be detected by the naked eye. In pregnant animals, the most notable features of the disease are: abortions, newborn weakness and infertility. At dairy farms, the largest economic losses are caused by a decrease of milk production, as well as by an alteration in the lactation cycles due to miscarriages and a decline in conceptions per animal. Not all infected animals abort, but those that do, spontaneously abort during the final stages of gestation. Infections called endometriosis occur in the uterus, as a result of the miscarriage.

Infected animals permanently host and shed Brucella bacteria into the environment, which is the source of the disease. Brucella is sensitive to direct sunlight, disinfectants and to pasteurization. Under optimal conditions, it survives in water, wet soil, urine, aborted foetuses and uterine exudates.

Aborted foetuses, placental membranes and other vaginal discharges are highly contaminated with Brucella, which in turn contaminate water and food supply. The main form of infection is via the digestive route; it occurs when animals lick placentas and aborted foetuses, and graze on contaminated fields, leading to a massive ingestion of Brucella bacteria. Brucellosis is also transmitted by direct contact between animals. Farms can also be contaminated by the introduction of infected animals, or wild animals.
 
Many countries are adopting control and eradication programs against Brucellosis. As with other diseases, the success of a control plan depends primarily on the farmer’s support and participation. As part of these programs, animals are subjected to regular diagnostic tests, where the culling of infected animals is carried out in order to isolate the infection at source. In risk areas, animals must be vaccinated to prevent infection. To ensure a program’s success, it is essential that the animal’s movements be controlled.

There is no treatment for brucellosis in animals; this is because Brucella usually lodges in the white blood cells that protect the animal, and consequently antibacterial substances fail to act. However, the disease can be prevented, controlled and even eradicated by using vaccines, coupled with good management and hygiene practices.