The gram-negative bacterium, C. burnetii, causes Q Fever. C. burnetti infects cattle, sheep, and goats, among other animals. The primary reservoir for human exposure to Q Fever are cattle, sheep, and goats. C. burnetii is found in the urine, feces, milk, and birth products such as the placenta of infected animals. Q Fever is spread by inhaling contaminated dust from the soil where infected animals have been. People can also be infected with C burnetii by ingesting contaminated unpasteurized milk and other dairy products. Vertical transmission to the infant during delivery and sexual transmission is also possible. Due to the low infectious dose required to infect humans, as few as ten bacteria, and the environmental stability of C. burnetti, C burnetti is classified as a Category B bioterrorism agent. In the United States, Q Fever is a reportable disease. In the past twenty years, fewer than 200 cases of Q Fever have been reported annually in the United States. However, the seroprevalence of Q Fever in the United States is around 3 percent and over 20 percent in veterinarians. The high seroprevalence rate of Q Fever in the United States suggests that many cases of Q Fever go undiagnosed and unreported. People at the highest risk of developing Q Fever are individuals exposed to cattle, goats, and sheep, such as farmworkers, veterinarians, and slaughterhouse workers, as well as individuals who work in animal laboratories and laboratories with C. burnetti cultures. Initial infection with Q Fever is usually an acute pulmonary infection or hepatitis with flu-like symptoms and a prolonged fever. Treatment for Q Fever is with doxycycline for two weeks with an alternative therapy of cotrimoxazole or rifampin. Up to 30 percent of acute Q Fever infections are associated with Q Fever Fatigue Syndrome that can last for several years or longer. Fewer than five percent of acute Q Fever cases will go on to develop chronic Q Fever. The most common form of chronic Q Fever is endocarditis. Additionally, chronic Q Fever can cause chronic hepatitis, osteomyelitis, osteoarthritis, and chronic pneumonitis. Treatment for chronic Q Fever is with the combination of doxycycline plus hydroxychloroquine for at least a year and a half (18 months). There is a vaccine for Q Fever that is only commercially available in Australia. The Q Fever vaccine is called Q-Vax. Pre-screening for previous Q Fever exposure with antibody titers are required for Q-Vax administration due to the potential for severe complications in the case of prior exposure to Q Fever.

References:

Dragan AL, Voth DE. Coxiella burnetii: international pathogen of mystery. Microbes Infect. 2020 Apr;22(3):100-110. DOI: 10.1016/j.micinf.2019.09.001.

Cherry C, Kersh GJ. Q Fever. In: Boulton ML, Wallace RB. eds. Maxcy-Rosenau-Last Public Health & Preventive Medicine, 16e. McGraw Hill; 2022.