Q-fever; Its Not a Query Anymore!

Emily Janovyak, DVM, USDA ORISE Fellow

If you keep small ruminants, chances are you’ve heard of Q-fever. But did you know that it can affect many other species, including humans? Q-fever is caused by Coxiella burnetii, a bacteria that infects the cells of host animals. It was recognized as a human disease in the mid 1930’s, when the ‘Q’ stood for ‘query’ (question) because cause of this disease was not known. Q-fever is present worldwide. In the United States, cases of human infection must be reported to health authorities whereas animal cases are monitored but reporting of cases is not required.  Surveys indicate a high prevalence of infected animals in the USA but, according to the CDC, only 1-2 hundred cases in humans each year.

Coxiella burnetii can infect many species of mammals, birds, and arthropods. But it is most significantly a problem with ruminants. Animals can transmit the disease by direct contact, either inhaling or ingesting the bacteria from the amniotic fluid/placenta, milk, urine, or feces of infected animals. It can persist in the environment for weeks to months, so contaminated pastures can be a source of infection. Some ticks can also transmit the disease, although ticks are not a significant source of infections. Most human cases come from populations who have had contact with infected tissues such as veterinarians, farmers, or slaughterhouse workers. Consuming raw (unpasteurized) milk has also been a source of infection in humans.

In animals, infection can cause loss of appetite, late term abortions, and ‘abortion storms;’ high numbers of abortions happening all at once in the same flock or herd. However, infected animals are often asymptomatic even though they still shed the bacterium. In humans it may cause a range of flu-like symptoms and can cause abortion in pregnant women.

The ADDL offers two tests for Q-fever, serology and PCR. Veterinarians attending sick or aborting animals will determine which test is applicable. The serology test is a complement fixation (CF) test, a multi-step process that tests for the presence of antibodies in the patient’s serum. This result indicates if the patient’s body responded to the presence of the bacteria. For PCR testing, which tests for genetic material from the bacteria itself, placenta is the most valuable specimen to test because the bacterium has an affinity for placental tissue. Although it is a bacteria, it is not cultured in the lab due to the high risk to humans directly handling the organisms. Please check the ADDL website for test fees and scheduled testing days.

Treatment is of limited efficacy. If abortions do occur in your herd or flock, carefully collect fetal tissue and fluid, especially placenta, for your veterinarian to submit for testing. The best control comes from practicing careful hygiene, especially around parturition. Clean barns/birthing areas thoroughly, limit human exposure by wearing gloves and masks, and do not have higher-risk individuals, such as pregnant women, handle potentially infected tissues. In short, the best defense against Q-fever is to keep things s-Q-ueeky clean!