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Brucellosis
Brucellosis is an infectious disease caused by bacteria in the genus Brucella. Brucella are aerobic, gram-negative coccobacilli. Brucellosis is a zoonotic infection, occurring mainly in animals but occasionally transferring to humans. It has various names such as Mediterranean fever, Malta fever, undulant fever, Crimean fever, Bang’s disease, and gastric remittent fever. Brucellosis is found in North-American wild animals (elk, bison) and occasionally in domesticated animals (cattle, pigs, sheep, and goats). The major species of Brucella that cause the disease are B. melitensis, B. suis, B. abortus, and B. canis, associated with sheep, pigs, cattle, and dogs respectively. The most pathogenic species are B. melitensis and B. suis.
Brucellosis was first described by Hippocrates and the Romans more than 2,000 years ago. In 1887, Dr. David Bruce isolated the organisms from patients on the island of Malta, hence the name Malta fever. The disease is found worldwide, with high-risk areas including Mediterranean countries, South and Central America, Eastern Europe, Africa, Asia, the Middle East, and the Caribbean. Fortunately, the annual number of infections in the United States is only about 100-200. California and Texas have the highest infection rates.
Highly pathogenic strains of Brucella can be used as a biological weapon since they can be aerosolized and easily inhaled.
Causes of brucellosis
Brucellosis is caused by bacteria. Brucella bacteria can enter the human body through mucous membranes, breaks in the skin, the respiratory tract, gastrointestinal tract, and even the conjunctiva. These bacteria can survive well within the body’s cells and be transported via the lymphatic system or bloodstream to other organs. They can also replicate inside host cells and then be released upon cell death to infect other cells.
The most common way individuals become infected with brucellosis is by consuming unpasteurized or raw dairy products from infected animals. Inhalation of bacteria is another possible route, mainly for those working in laboratories or meat-processing areas. The bacteria can also enter through breaks in the skin or mucous membranes. Infected animals that are hunted, such as caribou, moose, wild hogs, elk, and bison, may contain Brucella and pose a risk for transmission. Person-to-person transmission is rare but can occur through various means, such as sexual contact, blood transfusions, transplacental transfer, or contact with menstrual blood.
The U.S. Centers for Disease Control and Prevention (CDC) states that brucellosis is weakly contagious. However, it can be easily contracted by consuming unpasteurized or raw dairy products, inhaling aerosolized bacteria, or through breaks in the skin or mucous membranes.
Brucellosis remains contagious as long as living bacteria are present in domestic and wild animals and their secretions, including milk products. The bacteria can also survive in the environment for up to two years under favorable conditions and still cause disease.
Symptoms of brucellosis
Brucellosis can cause a wide range of symptoms. Some early symptoms include fever, fatigue, sweating, muscle and joint pain, abdominal pain, back pain, loss of appetite, weight loss, cough, headache, and swollen lymph nodes. Over time, fevers may become recurrent with night sweats, joint pain may worsen, and organ swelling may occur in the heart, testicles, liver, and spleen, leading to decreased organ function. Skin rash, micro-abscesses in the skin, chronic fatigue, depression, and neurologic symptoms may also develop. Symptoms typically appear two to four weeks after initial exposure, but the incubation period can vary widely.
Diagnosis of brucellosis
Diagnosis is based on the patient’s history of exposure and clinical symptoms. Confirmation is made through culturing Brucella bacteria from the patient and serological tests for specific antibodies. These tests help differentiate brucellosis from other similar diseases.
Treatment of brucellosis
Doxycycline and rifampin are the recommended antibiotic combination for treating brucellosis, usually for a minimum of six to eight weeks. Long-term treatment is necessary due to the ability of Brucella to survive within human cells. Immunosuppressed individuals and pregnant patients should be treated in consultation with specialists. Home remedies for brucellosis lack scientific evidence of effectiveness and should be discussed with healthcare providers.
Prognosis for brucellosis
If treated appropriately within the first few months of symptom onset, the prognosis for brucellosis is generally good, with complete resolution of symptoms within two to six months. However, chronic organ damage can occur in some individuals, affecting the heart, nervous system, or genitourinary system. The mortality rate for brucellosis is low.
Prevention of brucellosis
Brucellosis can be prevented by avoiding infected animals, not consuming unpasteurized milk, and taking precautions when in contact with potentially infected animals. Vaccines for livestock are available, but no vaccine exists for human use.
