Brucellosis in animals and humans
Causes
Brucellosis is an infectious disease that occurs from contact with animals carrying Brucella bacteria. Brucella can infect cattle, goats, camels, dogs, and pigs. The bacteria can spread to humans if you come in contact with infected meat or the placenta of infected animals, or if you eat or drink unpasteurised milk or cheese.
Brucella is highly contagious, spreading very easily between cattle as the calf, the membranes and the uterine fluids all contain large quantities of bacteria.
Natural transmission occurs by ingestion of organisms, which are present in large numbers in aborted fetuses, fetal membranes, and uterine discharges. Cattle may ingest contaminated feed and water or may lick contaminated genitals of other animals. Venereal transmission by infected bulls to susceptible cows appears to be rare. Transmission may occur by artificial insemination when Brucella-contaminated semen is deposited in the uterus but, reportedly, not when deposited in the midcervix. Brucellae may enter the body through mucous membranes, conjunctivae, wounds, or intact skin in both people and animals.
Symptoms
Abortion is the most obvious manifestation. Infections may also cause stillborn or weak calves, retained placentas, and reduced milk yield. Usually, general health is not impaired in uncomplicated abortions.
Seminal vesicles, ampullae, testicles, and epididymides may be infected in bulls; therefore, organisms are present in the semen. Agglutinins may be demonstrated in seminal plasma from infected bulls. Testicular abscesses may occur. Longstanding infections may result in arthritic joints in some cattle.
Signs of disease in people are tiredness, headaches, night sweat, muscle pain and loss of appetite.
Prevention
Prevention of brucellosis in animals
Prevention involves vaccination and testing of the blood of the animals.
All female calves are vaccinated between 4 and 8 months of age. A live vaccine is used and it is best that it is injected by your veterinarian or animal health technician. Pregnant animals must not be vaccinated, because they will abort
Cows should also be bled by your state veterinarian or animal health technician yearly to check if they are free of brucellosis.
Note that abortion can be caused by many different diseases, of which brucellosis is one of the most important. Some of these may be spread by the bull. If your cows are aborting it is very important to get the cause identified by your state veterinarian. Care must be taken when handling aborted calves. Wear gloves to protect you from becoming infected.
Prevention of brucellosis in humans
The prevention of human brucellosis is based on occupational hygiene and food hygiene.
Vaccination is not generally recommended.
All dairy products should be prepared from heat-treated milk.
Consumption of raw milk or products made from raw milk should be avoided.
Meat should be adequately cooked.
Special precautions should be taken by laboratory workers.
Physicians and health workers should be aware of the possibility of brucellosis.
Public health education should emphasize food hygiene and occupational hygiene.