Q fever, a disease transmitted from animals to humans, is caused by Coxiella burnetii (C. burnetii), an organism belonging to a family of infectious agents known as rickettsia. While often disregarded as being a potential pathogen in the realm of human and veterinary medicine, C. burnetii is distributed globally and a signifi-cant cause of disease around the world.
Coxiella burnetii is commonly found in a wide range of wild and domestic animals. Apart from abortions in sheep and goats, C. burnetii seldom causes clinical disease in domestic animals. However, cattle and small ruminants, in particular sheep and goats, have been associated with large outbreaks of disease in humans. Although domestic cats and horses are considered potential reservoirs for C. burnetii, their role as a potential cause of human disease is not fully understood.
Organisms are shed in feces, urine, placenta, fetal fluids, and milk. Q fever in humans is often associated with contact with cattle, sheep and goats at birthing when large numbers of organisms are shed in the fetal fluids of infected animals. Inhalation of airborne barnyard dust contaminated by
C. burnetii in dried placental material, birth fluids, and excreta of infected animals is another mode of transmission.
C. burnetii are resistant to heat, drying, and many common disinfectants and as a result survive for long periods in the environment.
Humans are very susceptible to Q fever. A small number of organisms (as few as 10 or less) are needed to establish infections in people. While many human infections are inapparent, about one-half of all people infected with C. burnetii show some signs of clinical illness. Most acute cases of Q fever begin with the sudden onset of “flu-like” symptoms including: high fevers (up to 40-40.6C/ 104-105F), severe headache, general malaise, muscle pain, sore throat, chills, sweats, non-productive cough, nausea, vomiting, diarrhea, abdominal pain, and chest pain. In more serious cases, Q fever can progress to pneumonia, hepatitis, brain infections and heart complications. Q fever has been reported as an important cause of atypical pneumonia. During a 1983 outbreak of Q fever in Nova Scotia, 20 per cent of all pneumonia cases admitted to regional hospitals were caused by Coxiella burnetii. More recently, the National Dutch Institute for Public Health and the Environment reported that between January and October 2009, 2,236 cases of Q fever were diagnosed in the Netherlands, primarily the result of contact with goat herds. There were many patients with respiratory and cardiac complications. At least six patients died.
In general, most patients recover to good health within several months without any treatment. Others require long-term treatment and a significant percentage of those eventually develop fatal complications.
Because the signs and symptoms of Q fever are not specific, an accurate diagnosis requires appropriate laboratory testing. Coxiella organisms can be detected microscopically in tissue samples from aborted fetuses.
Q fever outbreaks are frequently the result of occupational exposure. Veterinarians, meat-processing plant workers, sheep and dairy workers, livestock owners, and researchers at facilities housing sheep have all been victims. Farms and ranches with a blend of cattle, sheep and goats are becoming more common. A few basic precautions will help:
Abortions, especially those from sheep and goats, should routinely be reported to a veterinarian and submitted for diagnosis.
Appropriately dispose of placenta, birth products, fetal membranes, and aborted fetuses at facilities housing sheep and goats.
Restrict access to barns during calving/lambing/kidding season and exercise basic biosecurity measures (protective gloves, hand wash stations, clean outerwear).
Avoid unpasteurized milk and milk products.
Ron Clarke is a veterinarian who writes from Stony Plain, Alta.