|Common Name(s)||Brucellosis, Malta Fever, Bang's Disease|
|Physical Attributes||Small gram-negative, aerobic, non-motile coccobacilli that grow within monocytes and macrophages|
|Mode(s) of Transmission||Eating or drinking (especially milk products); inhalation; enter the body through skin wounds; breast-feeding; sexual intercourse; tissue transplants|
|Likely BW Form(s)||Aerosol|
|Pathology||Flu-like and may include fever, sweats, headaches, back pains, anorexia and physical weakness; severe infections affect central nervous systems or lining of the heart; can cause chronic symptoms that include recurrent fevers, joint pain, and fatigue; symptoms last for months|
|Host(s)||Human; animals (vertebrates)|
|Vector/Dormant Form||Cows as reservoirs; bacteria in domestic animals|
|Fatality||As high as 6% but usually less than 2%|
|Incubation Period||Ranges from 1 week-1 year|
|Vaccine||5 vaccines (RB51, strain 19, strain 2, Rev-1 and 45/20) for cattle and bison and|
|Treatment||Antibiotics: doxycycline (200 mg/day) plus rifampin (900 mg/day) for 6 weeks to prevent reoccuring infection|
Brucellosis is a systemic zoonotic disease caused by one of four species of bacteria: Brucella melitensis, B. abortus, B. suis, and B. canis; virulence for humans decreases somewhat in the order given. These bacteria are small gram-negative, aerobic, non-motile coccobacilli that grow within monocytes and macrophages. They reside quiescently in tissue and bone-marrow, and are extremely difficult to eradicate even with antibiotic therapy. Their natural reservoir is domestic animals, such as goats, sheep, and camels (B. melitensis); cattle (B. abortus); and pigs (B. suis). Brucella canis is primarily a pathogen of dogs, and only occasionally causes disease in humans. Humans are infected when they inhale contaminated aerosols, ingest raw (unpasteurized) infected milk or meat, or have abraded skin or conjunctival surfaces that come in contact with the bacteria. Laboratory infections are quite common, but there appears to be no human-to-humantransmission; isolation of infected patients is, therefore, not required.
Brucella species long have been considered potential candidates for use in biological warfare. The organisms are readily lyophilized, perhaps enhancing their infectivity. Under selected environmental conditions (for example, darkness, cool temperatures, high C02), persistence for up to 2 years has been documented. When used as a biological warfare agent, Brucellae would most likely be delivered by the aerosol route; the resulting infection would be expected to mimic natural disease.
Brucellosis presents after an incubation period normally ranging from 1-4 weeks, but may be as short as 1 week or as long as a year. Clinical disease presents typically as an acute, non-specific febrile illness with chills, sweats, headache, fatigue, myalgias, arthralgias, and anorexia. Cough occurs in 15-25%, but the chest x-ray usually is normal. Complications include sacroiliitis, arthritis, vertebral osteomyelitis, epididymo-orchitis, and rarely endocarditis. Physical findings include Iymphadenopathy in 10-20% and splenomegaly in 20-30% of cases. Untreated disease can persist for months to years, often with relapses and remissions. Disability may be pronounced. Lethality may approach 6% following infection with B. melitensis, but the disease is rarely fatal (0.5% or less) after infection with other serotypes (usually after endocarditis develops).
The initial symptoms of brucellosis are usually nonspecific, and the differential diagnosis is therefore very broad and includes bacterial, viral, and mycoplasmal infections. The systemic symptoms of viral and mycoplasmal illnesses, however, are usually present for only a few days, while they persist for prolonged periods in brucellosis. Brucellosis may be indistinguishable clinically from the typhoidal form of tularemia or from typhoid fever itself. The disease in humans is characterized by a multitude of somatic complaints, including fever, sweats, anorexia, fatigue, malaise, weight loss, and depression. Localized complications may involve the cardiovascular, gastrointestinal, genitourinary, hepatobiliary, osteoarticular, pulmonary and nervous systems. Without adequate and prompt antibiotic treatment, some patients develop a 'chronic' brucellosis syndrome with many features of the 'chronic fatigue' syndrome.
The recommended treatment is doxycycline (200 mg/day) plus rifampin (900 mg/day) for 6 weeks. Alternative effective treatment consists of doxycycline (200 mg/day) for 6 weeks plus streptomycin (1 gm/day) for 3 weeks. Trimethoprimsulfamethoxazole given for 4-6 weeks is less effective. In 5-10% of cases, there may be relapse or treatment failure. Laboratory infections with brucellosis are quite common, but there is no human-to-human transmission and isolation is not required.
Five vaccines are manufactured for cattle and bison. Killed and live attenuated human vaccines have been available in many countries but are of unproven efficacy. There is no information on the use of antibiotics for prophylaxis against human brucellosis.
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