Q- fever (Coxiella burnetti) has both acute and chronic stages. Modes of transmission to humans, include tick bites, ingestion of unpasteurized milk or dairy products, and human to human transmission. Humans are often very susceptible to the disease, and very few organisms (even one) are all that are needed to cause infection.
Cattle, sheep, and goats are the primary host reservoirs although a variety of animals may be infected. C. burnetti organisms are excreted in milk, urine, and feces of infected animals. During birth, organisms are shed in high numbers within the aborted amniotic fluids and the placenta.
The hardy organism is resistant to heat, drying and many common disinfectants, which enables 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 with dried placental material, birth fluids and excreta of infected animals.
The following is a list of symptoms commonly seen with acute or chronic Q-fever. It is important to note that the combination of symptoms varies greatly from person to person.
- high fevers (up to 104-105°F)
- flu-like symptoms
- severe headache
- general malaise
- upper respiratory problems
- chills and/or sweats
- non-productive cough
- loss of appetite
- liver enlargement
- abdominal pain
- chest pain
- atypical pneumonia
- difficulty sleeping
- retinal vasculitis
- mood changes
- severe fatigue
- infections in bones
- infections in reproductive organs
- aortic aneurysms
Although most people with Q-fever infection recover, others may experience serious illness with complications that may include pneumonia, granulomatous hepatitis (inflammation of the liver), myocarditis (inflammation of the heart tissue) and central nervous system complications. Pregnant women who are infected may be at risk for pre-term delivery or miscarriage.
Chronic Q-fever is a severe disease occurring in <5% of acutely infected patients. It may present soon (within 6 weeks) after an acute infection, or may manifest years later. The three groups at highest risk for chronic Q-fever are pregnant women, immunosuppressed persons and patients with a pre-existing heart valve defects. Endocarditis is the major form of chronic disease, comprising 60-70% of all reported cases. The estimated case fatality rate in untreated patients with endocarditis is 25-60%.
Patients with endocarditis require early diagnosis and long-term antibiotic treatment (at least 18 months) for a successful outcome. Other forms of chronic Q-fever include aortic aneurysms and infections of the bone, liver or reproductive organs.
Coxiella burnetii has the ability to persist for long periods of time in the host after infection. Although the majority of people with acute Q-fever recover completely, a post-Q-fever fatigue syndrome has been reported to occur in 10-25% of some acute patients. This syndrome is characterized by constant or recurring fatigue, night sweats, severe headaches, photophobia (eye sensitivity to light), pain in muscles and joints, mood changes, and difficulty sleeping.
Diagnosis and Treatment
Q-fever can be diagnosed by antibody testing of blood. Antibiotics commonly used for treatment are doxycycline, tetracycline, chloramphenicol, ciprofloxacin, ofloxacin, and hydroxychloroquine. The chronic form of Q-fever is more difficult to treat and can require up to four years of doxycycline and quinolones, or doxycycline with hydroxychloroquine.