Brucellosis is an infectious disease caused by a type of bacteria called Brucella. The bacteria can spread from animals to humans.
There are several different strains of Brucella bacteria. Some types are seen in cows. Others occur in dogs, pigs, sheep, goats, and camels. Recently, scientists have seen new strains in the red fox and certain marine animals, including seals. Brucella in animals cannot be cured.
Brucellosis is rare in the U.S. because of effective animal disease control programs. Fewer than 200 people get sick with the disease each year in the U.S. It is most often seen in the spring and summer months in:
Brucellosis is considered a significant health threat in other parts of the world. The disease has been reported in more than a half-million people each year in 100 countries, according to the World Health Organization.
What Causes Brucellosis?
Brucellosis in humans occurs when a person comes into contact with an animal or animal product infected with the Brucella bacteria.
Very rarely, the bacteria may spread from person to person. Breastfeeding moms with brucellosis may pass the bacteria to their baby. Brucella may also be spread through sexual contact.
The bacteria can enter your body:
- Through a cut or scratch in the skin
- When you breathe in contaminated air (rare)
- When you eat or drink something contaminated with the bacteria, such as unpasteurized milk or undercooked meat
Four types of Brucella bacteria cause the majority of brucellosis infections in humans:
B. melitensis . This type causes most cases of human brucellosis and is mainly found in sheep and goats. It is most often seen in:
- Latin America
- Middle East
B. suis . This infection found in wild pigs is the most common type of Brucella seen in the U.S. Brucellosis due to this strain most often occurs in the Southeast and California. It also occurs in Europe, South America, and Southeast Asia.
B. canis. The infection from this type of bacteria spreads from dogs. It is most often seen in:
- North, Central, and South America
- Central Europe
B. abortus . This infection comes from cattle. It occurs worldwide. It has been wiped out in several European countries, Japan, Israel, Canada, Australia, and New Zealand.
Can I Get Brucellosis From My Dog?
Dogs can become infected with B. canis. Some pet owners have developed brucellosis this way but the disease is usually mild. There is at least one known case of brucellosis spreading to a human by a dog bite. But spreading brucellosis this way is uncommon. Most dogs infected with Brucella do NOT spread the bacteria to their owners.
You are more likely to get brucellosis from an infected dog if you come in contact with blood or other fluids from the animal. Veterinarians have an increased risk of brucellosis.
If you have a weakened immune system due to medications or certain diseases, you should not touch dogs that are infected with Brucella.
What Are the Risk Factors for Brucellosis?
In the U.S., brucellosis is more common in men. Men who become sick with the disease most often work or have worked around livestock. Brucellosis is uncommon in children.
You are more likely to get brucellosis if you:
- Eat or drink unpasteurized dairy products from cows, goats, or other animals that are infected with the bacteria
- Eat other unpasteurized cheeses called "village cheeses." These come from high-risk regions, including the Mediterranean
- Travel to areas where Brucella is common
- Work in a meat-processing plant or slaughterhouse
- Work on a farm
Brucellosis has also been reported in:
- Hunters in the U.S.
- Veterinarians who have immunized cattle with the Brucellavaccine
What Are the Symptoms of Brucellosis?
General symptoms of brucellosis are often vague and similar to the flu. They may include:
- Fever (the most common symptom, with high "spikes" that usually occur in the afternoon)
- Back pain
- Body-wide aches and pains
- Poor appetite and weight loss
- Night sweats
- Abdominal pain
Symptoms usually appear within five to 30 days after you come in contact with the bacteria. How bad your symptoms are depends on what type of Brucella is making you sick:
- B. abortus usually causes mild or moderate symptoms, but they are more likely to become chronic (long-lasting).
- B. canis symptoms may come and go. They are similar to B. abortus infection, although people with B. canis often have vomiting and diarrhea.
- B. suis may cause areas of infection (called abscesses) in different organs.
- B. melitensis may cause sudden and severe symptoms, which may lead to disability.
How Is Brucellosis Diagnosed?
Your doctor will examine you. You may have:
- A swollen liver
- Swollen lymph nodes
- A swollen spleen
- Unexplained fever
- Joint swelling and pain
- A rash
Blood tests will be done to diagnose the infection and determine what type of Brucella is making you sick. Proper identification of the bacteria helps pinpoint the source of the infection.
How Is Brucellosis Treated?
You will generally be given doxycycline and rifampin a in combination for 6-8 weeks.
You must take the antibiotics for many weeks to prevent the disease from returning. The rate of relapse following treatment is about 5-15% and usually occurs within the first six months after treatment.
Recovery can take weeks, even months. Patients who receive treatment within one month of the start of symptoms can be cured of the disease.
What Are the Complications of Brucellosis?
Severe brucellosis may cause:
- Infection of the central nervous system
- Endocarditis (infection of the lining of the heart or valves)
- Liver abscess
Brucellosis can cause long-lasting symptoms that are similar to systemic exertion intolerance disease. SEID is formerly known as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. The symptoms can lead to disability. They may include:
Brucellosis in a pregnant woman may lead to:
Death from brucellosis is uncommon. Most brucellosis-related deaths are due to endocarditis.
How Can I Prevent Brucellosis?
Brucellosis may be prevented with the following steps:
- Do not drink or eat unpasteurized dairy products.
- Wear rubber gloves if you work in the animal processing industry.
If you have come in contact with an animal infected with Brucella, tell your health care provider -- even if you do not have symptoms. You will need to be monitored for at least six months. There is no effective human vaccine to prevent brucellosis.