Q fever is an infectious disease affecting livestock and humans that’s caused by the bacteria Coxiella burnetii. Sheep, goats and cattle can all carry the organism. Ticks are rarely the source of transmission, but they’re still viable carriers. Regular treatment for and prevention of external parasites is just as important as internal parasites in the case of Q fever.
C. burnetii can be shed in infected animals’ urine, feces and milk, as well as in vaginal secretions and uterine fluids released from infected animals during birthing and in the days and weeks following. During this time, the dam, offspring, and birthing membranes and fluids can all appear perfectly healthy, despite carrying the bacteria.
Q fever can also result in visible signs of disease in infected animals, especially with does and ewes. Infected animals might give birth to weak offspring or abort. When a doe or ewe aborts because of Q fever, C. burnetii is present in extremely high concentrations in the aborted fetus, uterine fluids and placenta—the latter of which might be visibly thickened. If there’s an abortion outbreak in a herd or flock, Q fever should be considered a possible cause. Definitive diagnosis requires testing of aborted fetuses and placentas. While owners can submit samples directly to their state veterinary diagnostic lab for analysis, it’s much more prudent to have a veterinarian do so, as he or she is trained on how to safely handle, package and transport infectious materials. A veterinarian can also examine the animals and offer potential treatments and preventive strategies for specific diseases that cause abortion in livestock.
Although a vaccine has been developed in Australia, there is no licensed vaccine to prevent Q fever in livestock in the U.S. Once infection is confirmed as a cause of abortion, treatment of other pregnant does or ewes with tetracycline might decrease the risk of further abortions, but it’s unlikely to eliminate the problem entirely.
Because most animals infected with Q fever are asymptomatic, prevention is difficult. However, good biosecurity practices can reduce chances of the disease spreading within your herd or flock. Quarantine any newly purchased or acquired animals from pregnant cows, does or ewes until all animals have birthed; it’s generally safer to add new animals to the herd when cows, ewes or does are not pregnant. If there’s an abortion, dispose of any bedding or equipment that came into contact with tissues or fluids as hazardous, infectious waste. Clean contaminated surfaces with dish soap and water and sterilize with a phenolic disinfectant, such as Lysol. Immediately isolate animals that abort from the remainder of the herd until diagnostic testing is complete.
C. burnetii can also infect humans. Transmission typically occurs through inhalation of microorganisms that become airborne when an infected animal gives birth or spontaneously aborts. Pasteurization eliminates the organism from milk, cheese, yogurt and other dairy products; therefore, ingestion of non-pasteurized milk or milk products represents a potential risk of infection.
Most (about 60 percent) of healthy humans infected with Q fever develop no symptoms and eliminate the infection through a successful immune response. If symptoms develop, they’re typically flu-like in nature (fever, headache, cough, fatigue, muscle aches, diarrhea and vomiting) and usually appear one to three weeks after exposure. Acute cases that don’t resolve spontaneously often resolve after two or three weeks of antibiotic treatment.
Complications, such as pneumonia and liver infection, can occur in people with impaired immune systems, and Q fever can also cause endocarditis in people with heart-valve defects or coronary vascular grafts. Q fever can cause complications during pregnancy. Individuals at high risk of developing complications should consider limiting or avoiding contact with livestock during kidding, calving or lambing time; they should also avoid contact with materials and clothing contaminated with livestock manure or birthing fluids.
It’s vital that people at risk of contracting Q fever disclose this to their physician, as Q fever resembles many common ailments, such as influenza. Further, “flu season” typically overlaps with lambing, calving and kidding season, so clarification of your exposure to birthing or aborting livestock is essential for a rapid diagnosis.
In the U.S., Q fever in humans is a notifiable disease, primarily because of its status as a possible bioterrorism agent. Reporting usually isn’t required for animals unless associated with human infection.
Protect yourself by wearing disposable obstetric gloves and coveralls during kidding, lambing or calving. Consider adding eye protection and a protective mask when handling livestock, their manure or bedding, and soil from premises where they’ve been kept if you are at higher risk. All of this gear should always be worn when handling and disposing of aborted fetuses, stillborn or weak neonates, and birthing membranes. Contaminated clothing should be placed in a trash bag until it can be put into the washing machine and washed with hot water and laundry detergent; be sure to keep contaminated clothing out of the reach of children and pets until washed.
About the Authors: Dave Van Metre, DVM, DACVIM, is a professor at the Animal Population Health Institute in the College of Veterinary and Biomedical Sciences at Colorado State University. Dr. Lyle G. McNeal is a livestock specialist in the Department of Animal, Dairy and Veterinary Sciences at Utah State University.
This article first appeared in the January/February 2013 issue of Hobby Farms.