A few things to remember
Q fever is a disease caused by Coxiella burnetii. Many animals are susceptible to Q fever, though the primary reservoirs are cattle, goats, and sheep. It is a zoonotic disease, resulting in mild to severe and possibly chronic disease in people. Though the infection is rarely diagnosed, it may be more common than many veterinarians and physicians realize.
C. burnetii can be found in most places throughout the world. It is a hardy bacterium that can survive in the environment for prolonged periods of time. In livestock, infections tend to be asymptomatic but may cause abortions, decreased fertility, weak newborns, and other primarily reproductive issues. Once infected, animals may intermittently shed viable bacteria in varying amounts indefinitely in milk, feces, and reproductive secretions, with the highest volume of shedding during parturition and in the placenta and birthing fluids. In some livestock species, shedding is highest during the first and second pregnancies.
People are typically exposed to the bacteria while assisting animals with birthing, through close contact with infected animals or their birthing products, or by breathing in contaminated dust or aerosols. Contact with animals and or their contaminated environments are recognized as higher risk exposures for Q fever, but direct contact is not necessary as the organism has the potential to become airborne and travel on wind currents. Less common routes of exposure include consumption of unpasteurized dairy products and tick bites. Roughly half of exposed persons will remain asymptomatic, while others may develop mild flu-like illness, pneumonia, or hepatitis. Chronic disease develops in <5% of all infected persons, manifesting primarily as endocarditis but also as rare vascular infections, granulomatous infections of bone and liver, or recurrent miscarriages. People with heart valve disorders, immunosuppressive conditions, and pregnant women are at increased risk for developing chronic Q fever. Long-term fatigue has also been associated with human infections.
During 2011, a goat-associated outbreak of Q fever occurred in Washington and Montana. Human infections are usually infrequent in both states (0-3 cases per year). In April 2011, C. burnetii was detected in a placenta collected from a goat farm in Washington, where the herd had experienced an increased number of abortions. Soon after this diagnosis, human infections were diagnosed among persons who had purchased goats. An outbreak investigation involving 21 farms in Washington, Montana, and Oregon identified 20 human cases, including goat owners, farm visitors, and neighbors. Evidence of infection in goats was detected in nearly all 17 herds tested. A herd management plan was implemented, advising goat owners to: wear protective clothing and boots while working with animals and remove contaminated or soiled barn clothing prior to entering their homes; use good hand hygiene and thoroughly wash hands after farm work; disinfect birthing areas; compost manure instead of spreading it on the field; segregate newly acquired animals; maintain a detailed animal registry including purchases, sales, and adverse pregnancy events; and report animal abortions to their veterinarians.
Continued community awareness is essential for disease prevention and control. Although the outbreak last year was associated with goats, many animals are susceptible and the infection can be spread between species. Investigation and surveillance of Q fever by both animal health and public health authorities relies on recognition, diagnosis, testing, and reporting by veterinarians, physicians, and other veterinary and healthcare professionals. Already in 2012, two human cases of Q fever have been reported. Although no animal contact has been identified for one, and the other was likely exposed out of the country, the presence of C. burnetii in livestock and the environment in our state warrants awareness of the possibility for exposures to occur especially during the birthing (lambing, kidding, calving) season. Spring fairs, petting zoos, livestock sales, and other venues bringing people and animals together present the potential for exposure to many zoonotic agents including Q fever.
We urge veterinarians to be aware of Q fever, recognizing both animal disease and the zoonotic potential. Animal infections are reportable to the Washington State Department of Agriculture, and warrant collaboration with public health officials to investigate potential human cases, advise owners about the risk of human disease, and provide recommendations for reducing exposure. Human cases are reportable to local health departments.
For more information:
By Nicola Marsden-Haug, MPH (Zoonotic Disease Epidemiologist) and Ron Wohrle, DVM (Public Health Veterinarian), Washington State Department of Health