Brucellosis is an infectious disease caused by the Brucella bacteria. These bacteria are primarily passed among animals, and they cause disease in many different vertebrates. Various Brucella species affect sheep, goats, cattle, deer, elk, pigs, dogs, and several other animals. Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria.
 

Humans generally get infected by either eating or drinking something that is contaminated with Brucella, breathing in the organism (inhalation), or having the bacteria enter the body through skin wounds. Eating or drinking contaminated milk products is the most common way to get infected. When sheep, goats, cows, or camels are infected, their milk is contaminated with the bacteria. If the milk is not pasteurised, these bacteria can be transmitted to persons who drink the milk or eat cheese made from it.

Inhalation of Brucella organisms is not a common route of infection, but it can be a significant hazard for people in certain occupations, such as those working in laboratories where the organism is cultured. Inhalation is often responsible for a significant percentage of cases in abattoir employees.

Contamination of skin wounds may be a problem for persons working in slaughterhouses or meat packing plants or for veterinarians. Hunters may be infected through skin wounds or by accidentally ingesting the bacteria after cleaning deer, elk, moose, or wild pigs that they have killed.

The illness may be chronic and persists for years. People working in occupations requiring frequent contact with animals or meat, such as slaughterhouse workers, farmers, and veterinarians, are at high risk. Brucellosis can be very common in countries where animal disease control programmes have not reduced the amount of disease among animals.

Direct person-to-person spread of brucellosis is extremely rare. Mothers who are breast feeding may transmit the infection to their infants. Sexual transmission has also been reported. For both sexual and breast-feeding transmission, if the infant or person at risk is treated for brucellosis, their risk of becoming infected will probably be eliminated within 3 days. Although uncommon, transmission may also occur via contaminated tissue transplantation.

In humans, brucellosis can cause a range of symptoms that are similar to the flu and may include fever, sweats, headaches, back pains, and physical weakness. Severe infections of the central nervous systems or lining of the heart may occur. Brucellosis can also cause long-lasting or chronic symptoms that include recurrent fevers, joint pain, and fatigue.

Acute brucellosis may begin with mild flu-like symptoms or with fever, chills, sweating, muscle aches (myalgia), joint aches and malaise. Usually, fever occurs every afternoon to levels around 104 degrees Fahrenheit. Other symptoms may include weakness, weight loss, fatigue, headache, abdominal pain, back pain, loss of appetite, joint pain or swollen glands.

Brucellosis is diagnosed in a laboratory by finding Brucella organisms in blood or bone marrow culture. Also, blood tests can be done to detect antibodies against the bacteria. If this method is used, two blood samples should be collected 2 weeks apart. Other tests are:

• Urine culture
   
• CSF culture
   
• Serology detecting brucellosis antigen

A combination antibiotic therapy, such as doxycycline and rifampicin or an aminoglycoside, is recommended to treat and prevent relapse of infection. Usually, doxycycline and rifampicin are used in combination for 6 weeks to prevent recurring infection. Longer courses of therapy may be required for complications. Depending on the timing of treatment and severity of illness, recovery may take a few weeks to several months.

Relapse may occur, and symptoms may persist for years. Reactivation can occur after a long period of time, as with tuberculosis. Mortality is low, and is usually associated with endocarditis.

Pasteurisation of milk and eating only pasteurised cheese are the most important preventive measures. Do not consume unpasteurised milk, cheese, or ice cream while travelling. If you are not sure that the dairy product is pasteurised, don't eat it.

People who handle meat should wear protective glasses and clothing and protect skin breaks from infection. Detecting infected animals controls the infection at its source. Vaccination is available for cattle, but not humans.