Brucellosis is an infection of domesticated and wild animals that can be transmitted to humans. It is caused by an organism of the genus Brucella. The organism infects mainly cattle, sheep, goats, and other similar animals causing death of developing fetuses and genital infection. Humans, who usually are infected incidentally by contact with infected animals, may develop numerous symptoms in addition to the usual ones of fever, general illness, and muscle pain.
The disease often becomes long-term and may return, even with appropriate treatment. The ease of transmission through the air suggests that these organisms may be useful in biological warfare.
Each of 6 different species may tend to infect certain animal species. Four are known to cause illness in humans. Animals may transmit organisms during a miscarriage, at the time of slaughter, and in their milk. Brucellosis is rarely, if ever, transmitted from human to human.
Certain species can enter animal hosts through skin abrasions or cuts, the eye membranes, the respiratory tract, and the GI tract. Organisms grow rapidly and eventually go to the lymph nodes, liver, spleen, joints, kidneys, and bone marrow.
Signs and symptoms
Victims may have a fever or a long-term infection or just a local inflammation. The disease may appear suddenly or develop slowly anywhere from 3 days to several weeks after exposure. Symptoms include fever, sweats, fatigue, loss of appetite, and muscle or joint aches. Depression, headache, and irritability occur frequently. In addition, infection of bones, joints, or the genitourinary tract may cause pain. Cough and chest pain also may be noted.
Symptoms often last 3-6 months and occasionally for longer than a year. Different species of the organism can cause different symptoms from skin sores to low back pain to liver disease.
The doctor will want to know about any exposure to animals, animal products, or environmental exposures in making the diagnosis. Military troops exposed to a biological attack and who have fever are likely candidates for this illness. Environmental samples may show the presence of this organism in the attack area. Laboratory tests and cultures of blood or body fluid samples including bone marrow may be performed.
Therapy with a single drug has resulted in a high relapse rate, so a combination of antibiotics should be prescribed. A 6-week course of doxycycline along with streptomycin for the first 2 weeks is effective in most adults with most forms of brucellosis.
Animal handlers should wear appropriate protective clothing when working with infected animals. Meat should be well cooked, and milk should be pasteurized. Laboratory workers need to take appropriate cautions in handling the organism.
In the event of a biological attack, the standard gas mask should protect adequately from airborne species. No commercially available vaccine exists for humans.
Q fever is a disease that also affects animals and humans. It is caused by the bacteria Coxiella burnetii. A sporelike form of the organism is extremely resistant to heat, pressure, and many cleaning solutions. This allows the germs to live in the environment for long periods under harsh conditions. In contrast, the disease it causes in humans is usually not harmful, although it can be temporarily disabling. Even without treatment, most people recover.
The organism is extremely infectious. The potential of the organism as a biological warfare agent is related directly to its ability to infect people easily. A single organism is capable of producing infection and disease in humans. Different strains have been identified worldwide.
- Humans have been infected most commonly by contact with domestic livestock, particularly goats, cattle, and sheep. The risk of infection is increased greatly if humans are exposed while these animals are giving birth to young. Large numbers of the germs may be released into the air as an animal gives birth. Survival of the organism on surfaces, such as straw, hay, or clothing, allows for transmission to other people who are not in direct contact with infected animals.
- People can become infected by breathing the organisms.
Signs and symptoms
Humans are the only hosts that commonly develop an illness as a result of the infection. The illness may begin within 10-40 days. There is no typical pattern of symptoms, and some people show none at all. Most people appear mildly to moderately ill.
Fever (can go up and down and last less than 13 days), chills, and headache are the most common signs and symptoms. Sweating, aches, fatigue, and loss of appetite are also common. Cough often occurs later in the illness. Chest pain occurs in a few people. Sometimes there is a rash. Other symptoms such as headache, facial pain, and hallucinations have been reported.
Sometimes problems in the lungs are seen on chest x-rays. And some people may seem to have acute hepatitis because of their liver involvement. Others may develop a heart condition called endocarditis.
Blood tests may help in making the diagnosis of Q fever.
Tetracycline has been the main drug used since the 1950s. When initiated within the first few days of the illness, treatment significantly shortens its course. Other antibiotics, such as erythromycin and azithromycin, are also effective.
People with chronic Q fever who develop endocarditis may die, even with appropriate treatment.
Although an effective vaccine (Q-Vax) is licensed in Australia, all Q fever vaccines used in the United States are under study. Q fever can be prevented by immunization.