Doxycycline is the first line treatment for all adults, and for children with severe illness. Treatment should be initiated immediately whenever Q fever is suspected. Use of antibiotics other than doxycycline or other tetracyclines is associated with a higher risk of severe illness. Doxycycline is most effective at preventing severe complications from developing if it is started early in the course of disease. Therefore, treatment must be based on clinical suspicion alone and should always begin before laboratory results return.
If the patient is treated within the first 3 days of the disease, fever generally subsides within 72 hours. In fact, failure to respond to doxycycline suggests that the patient’s condition might not be due to Q fever. Severely ill patients may require longer periods before their fever resolves. Resistance to doxcycline has not been documented. There is no role for prophylactic antimicrobial agents in preventing Q fever after a known exposure and prior to symptom onset; attempts at prophylaxis will likely extend the incubation period by several days but will not prevent infection from occurring.
Q fever is a worldwide disease with acute and chronic stages caused by the bacteria Coxiella burnetii. Cattle, sheep, and goats are the primary reservoirs although a variety of species may be infected. Organisms are excreted in milk, urine, and feces of infected animals. During birthing the organisms are shed in high numbers within the amniotic fluids and the placenta. The organism is extremely hardy and resistant to heat, drying, and many common disinfectants which enable the bacteria to survive for long periods in the environment.
Infection of humans usually occurs by inhalation of these organisms from air that contains airborne barnyard dust contaminated by dried placental material, birth fluids, and excreta of infected animals. Other modes of transmission to humans, including tick bites, ingestion of unpasteurized milk or dairy products, and human to human transmission, are rare. Humans are often very susceptible to the disease, and very few organisms may be required to cause infection.
Coxiella Burnetti is a single species of genus Coxiella, family Rickettsiaceae, a short, rod-shaped bacterium. The gram-negative bacterium that grows preferentially in the vacuoles of the host cell and causes Q fever. It is distributed globally. Humans are very susceptible to infection, and the infectious dose may be very low.
There are several aspects of Q fever that make it challenging for healthcare providers to diagnose and treat. The symptoms vary from patient to patient and can be difficult to distinguish from other diseases. Treatment is more likely to be effective if started in the first three days of symptoms. Diagnostic tests based on the detection of antibodies will frequently appear negative in the first 7-10 days of illness.
The healthcare provider should also look at routine blood tests, such as a complete blood cell count or a chemistry panel. Clues such as a prolonged fever with low platelet count, normal leukocyte count, and elevated liver enzymes are suggestive of acute Q fever infection, but may not be present in all patients. After a suspect diagnosis is made based on clinical suspicion and treatment has begun, specialized laboratory testing should be used to confirm the diagnosis of Q fever.