Brucellosis is an infectious disease caused by the bacteria of the genus Brucella. 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. 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.

Causes

Brucellosis is caused by the bacterium Brucella. This bacterium infects domesticated animals. It can be spread to humans through:

• Drinking unpasteurized milk

• Eating dairy foods from infected cows, sheep, or goats

• Having direct contact with the secretions, excretions, or carcasses of infected animals

• Inhaling the bacteria

• Breastfeeding (passed from mother to infant)

• Sexual transmission

• Tissue transplantation

Risk Factors

A risk factor is something that increases your chances of getting a disease or condition. Risk factors for brucellosis include:

• Eating or drinking unpasteurized dairy foods, especially when traveling

• Working with domesticated animals and livestock, especially sheep, goats, cattle, deer, elk, and pigs, or their excretions, secretions, or carcasses

• Sex: male (possibly due to occupational exposure among farmers, ranchers, veterinarians, people working in tanneries, and slaughterhouse workers)

Symptoms

Symptoms of brucellosis usually appear within two weeks of infection. Symptoms can appear from five days to several months after infection.

In early stage, symptoms may include:

• Malaise

• Lethargy

• Headache

• Muscle pain

• Fever

• Chills

• Severe headache and backache

• Nausea, vomiting, and diarrhea

As it progresses, brucellosis causes a severe fever (104-105° F). This fever occurs in the evening along with severe sweating. It becomes normal or near normal in the morning, and usually begins again at night.

This intermittent fever usually lasts 1-5 weeks, after which symptoms usually subside or disappear for two days to two weeks. Then the fever recurs. In some patients, this fever recurs only once. In others, the disease becomes chronic, and the fever recurs, subsides, and then recurs again repeatedly over months or years.

In later stages, brucellosis can cause:

• Loss of appetite

• Weight loss

• Abdominal pains

• Headache

• Backache

• Joint pain

• Weakness

• Irritability

• Insomnia

Patients usually recover within 2–5 weeks. Rarely, complications can develop. These may include:

• Abscesses within the liver or spleen

• Enlargement of the liver, spleen, or lymph nodes

• Inflammation and infection of organs in the body, such as:

• • Heart (endocarditis)

• • Brain and brain lining (meningitis)

• • Bones (osteomyelitis), especially the spine

Brucellosis is also believed to cause a high rate of miscarriage during early pregnancy in infected women.

Diagnosis

Brucellosis is diagnosed in a laboratory by finding Brucella organisms in samples of blood or bone marrow. 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.

Treatment

Many patients recover from brucellosis on their own. However, early diagnosis and treatment can reduce the risk of complications and infection. Talk with your doctor about the best treatment plan for you. Treatment options include:

Antibiotics – your doctor may prescribe one or more antibiotics (usually doxycycline and rifampin) to control and prevent relapses of brucellosis. Antibiotics are given for up to six weeks.

Corticosteroids – these drugs, including prednisone, can help control symptoms (especially inflammation). They may be used for severe cases of brucellosis.

Prevention

To help reduce your chances of getting brucellosis, take the following steps:

• Avoid eating or drinking unpasteurized milk and dairy foods. If you are unsure if a dairy product is pasteurized, don’t eat it.

• Wear rubber gloves and goggles, and securely cover open wounds when handling domesticated animals including their secretions, excretions, or carcasses.

• Wear a protective mask when dealing with brucellosis cultures in the laboratory.

• Have cattle and bison that live in areas heavily infected with brucellosis vaccinated by an accredited veterinarian or government health official (the vaccine contains a live virus and is dangerous to humans). For best results, calves should be vaccinated when they are 4-6 months old. There is no brucellosis vaccine for humans as of yet.

RESOURCES:

Centers for Disease Control and Prevention
http://www.cdc.gov

National Foundation for Infectious Diseases
http://www.nfid.org

United States Department of Agriculture
http://www.usda.gov/

References:

Brucellosis. Division of Bacterial and Mycotic Diseases, Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/brucellosis_g.html. Accessed November 11, 2005.

Facts about brucellosis. US Department of Agriculture website. Available at: http://www.aphis.usda.gov/vs/nahps/brucellosis/. Accessed November 11, 2005.

The Merck Manual of Medical Information. Simon and Schuster, Inc.; 2000.

CDC