Last updated: October 19, 2010
Q fever is a disease caused by the rickettsial organism, Coxiella burnetti. Sheep are the most common carriers of the disease agent, but cattle, goats, and other warm-blooded animals, like birds, can also be affected. When animals are infected, Coxiella localizes to organs and tissues associated with reproduction, such as the uterus, placenta, mammary glands, and lymph nodes draining the mammary glands. Infection of the placenta may cause abortion. Large numbers of organisms may be discharged with the placenta, amniotic fluid, and dead fetuses. Some infected animals may become chronic carriers of Coxiella yet show no signs of disease.
Q fever is a concern when humans are working with sheep for research purposes, particularly when sheep are housed indoors. Coxiella burnetti is highly infectious, and only 1 to 10 infectious organisms are required to cause infection in humans. The highest risk of exposure is encountered when working with pregnant sheep, particularly during abdominal or fetal surgery or husbandry associated with lambing. Less commonly, the organism may also be encountered in contaminated animal bedding or human clothing or wool.
The incubation of Q fever in humans is 2 to 4 weeks. Clinical signs are suggestive of flu-like illness, including fever, chills, muscle aches, severe headache (typically behind the eyes), and profuse sweating. Nausea and vomiting is occasionally reported. The fever may last for 9 to 14 days and may recur later. The severity of disease is highly variable between individuals, so some persons with Q fever may show no signs at all while others become very ill. A chronic infection may develop in a small number of infected individuals, causing endocarditis, pneumonitis, pericarditis, and/or hepatitis. Persons at highest risk for cardiac-associated chronic disease are those with valvular disease or implants. Pregnant women infected with Coxiella burnetti may have abortions as a result of infection. The overall mortality rate in humans from Q fever is 1-2% in untreated cases and lower in treated cases.
Diagnosis of Q fever in humans is based on clinical signs, history of possible exposure, and blood testing for antibodies to Q fever. Generally, 2 blood samples collected 2 to 3 weeks apart are necessary for diagnosis. Treatment may be prescribed by a physician and is usually from the tetracycline family of antibiotics. Doxycycline is often used because of its convenient twice daily dosing.
Sheep can also be tested for the presence of antibodies against Coxiella burnetti. However, falsely negative tests are common, so antibody titers are not always reliable at accurately identifying sheep that do not carry the disease. Therefore, the Institutional Animal Care and Use Committee (IACUC) has developed a set of recommended practices to minimize the risk of exposure of research personnel to potentially infected sheep while not overly restricting the availability of research animals.
- All efforts will be made to use either wethers or non-pregnant female sheep in all IACUC sanctioned research projects at The University of Montana.
- If unsure of the pregnancy status, female sheep should have an abdominal ultrasound examination. Pregnant ewes will not be accepted for use in the Health Sciences Building Laboratory Animal Resources (LAR) facility.
- No abdominal or fetal surgical procedures in pregnant sheep are allowed in the Health Sciences Building LAR facility.
- Facilities housing sheep indoors will post a biohazard sign on the doors of rooms housing or using sheep. Surfaces in sheep housing and use areas will be disinfected with a fresh 1:10 dilution of household bleach (starting concentration of 5.25% sodium hypochlorite) as described in LAR facility standard operating procedures for sheep care. These protocols require 3 times weekly complete bedding changes/surface cleaning and 4 times weekly partial bedding changes/surface cleaning.
- If possible, sheep husbandry should be the last task of the day. Personal protective equipment to be used for sheep husbandry tasks in the HSB LAR facility includes shoe covers, scrubs, and latex or nitrile gloves. Personnel should wash their hands and forearms before leaving the sheep room. Personnel should always change into clean scrubs or street clothes after completing sheep husbandry tasks. Personnel experiencing any respiratory distress associated with complete bedding changes are encouraged to seek advice from the Occupational Health physician.
- Research personnel should follow standard operating room recommendations for USDA-regulated species. Personal protective equipment for surgical personnel should include face mask, hair covers, sterile gloves and gown, shoe covers, and surgical scrubs.
- Pregnant women, immunologically compromised individuals, and individuals with valvular heart disease or prosthetic heart valves should consult with the occupational health physician before beginning any work with sheep. If at all possible, these individuals should avoid work with sheep in LAR.
- Risk assessments of Q fever in the sheep housed at the sheep farm are conducted annually (with each new purchase of sheep) by testing for antibodies using complement fixation testing available at the National Veterinary Services Laboratory in Ames, Iowa. Each screening involves at least 25-30% of the new sheep flock, and all test results have been negative to date.