What is Q fever (Query fever)?

From the Guidelines

Q fever, also known as Cattleman's disease, is an infectious disease caused by the bacterium Coxiella burnetii that primarily affects people who work with livestock, especially cattle, sheep, and goats, and is characterized by high fever, severe headache, muscle pain, fatigue, and sometimes pneumonia or hepatitis. The disease spreads when humans inhale dust particles contaminated with infected animal fluids or waste. Symptoms typically include high fever, severe headache, muscle pain, fatigue, and sometimes pneumonia or hepatitis.

Key Characteristics of Q Fever

• The incubation period for Q fever is dose dependent, with the majority of infected persons having symptom onset 2–3 weeks after exposure, although onset can occur up to 6 weeks after exposure 1.
• Treatment usually involves doxycycline 100mg twice daily for 2-3 weeks, which is highly effective when started early, and should be administered immediately if fever occurs during the monitoring period 1.
• For pregnant women, trimethoprim-sulfamethoxazole is often used instead 1.
• Prevention measures include wearing protective equipment when handling livestock, proper disposal of animal birth products, and pasteurizing milk.
• The disease got its name from its common occurrence among cattle ranchers and farm workers who have regular contact with livestock.

Chronic Q Fever

• While most cases resolve with proper treatment, some patients may develop chronic Q fever, which can lead to serious complications like endocarditis and requires longer treatment courses of antibiotics, sometimes for years 1.
• Adults who receive a diagnosis of chronic Q fever should receive a treatment regimen of doxycycline and hydroxychloroquine, with a duration of treatment that might vary by the site of infection 1.
• Treatment for chronic Q fever should continue for at least 18 months for native valve infections and at least 24 months for prosthetic valve infections.

Monitoring and Treatment

• Baseline serologic testing can be performed to evaluate previous infection status with a convalescent sample drawn 6 weeks later to determine whether asymptomatic seroconversion has occurred 1.
• Serologic monitoring is recommended following acute Q fever infection to assess possible progression to chronic infection, with the recommended schedule for monitoring based on the patient’s risk for chronic infection 1.

From the Research

Definition and Cause of Q Fever

• Q fever is a zoonotic disease caused by the ubiquitous pathogen Coxiella burnetii, responsible for acute and chronic clinical manifestations 2, 3, 4, 5, 6.
• It is an obligate intracellular pathogen with a high infection capacity that proliferates exclusively in an acidified medium, forming a lysosome-like vacuole 3.

Transmission and Reservoirs

• The main reservoirs of infection are farm animals and pets, and transmission to humans is mainly accomplished through inhalation of contaminated aerosols 2, 3, 4, 6.
• Wild animals, domestic animals, and ticks are also principal reservoirs of the disease 3.
• Inhalation is the primary method of C. burnetii transmission in both people and animals, with smaller amounts occurring through milk and milk product ingestion 4.

Clinical Manifestations

• Q fever can manifest as an acute disease (mainly as a self-limited febrile illness, pneumonia, or hepatitis) or as a chronic disease (mainly endocarditis), especially in patients with previous valvulopathy and to a lesser extent in immunocompromised hosts and in pregnant women 2, 5, 6.
• The acute disease is more frequent and often asymptomatic, while a persistent focalized infection occurs in 4 to 5% of patients, generally with a poor evolution 3.
• Individuals presenting risk factors such as patients with valvular heart diseases and vascular prostheses, as well as pregnant women and immuno-suppressed patients represent a population at risk of chronic infection, with endocarditis as the most common clinical form 6.

Diagnosis and Treatment

• The diagnosis of Q fever is mainly made by indirect methods such as serology or by direct methods such as microbiological cultures or tests that detect the specific DNA 3, 4, 5.
• The treatment is effective and well tolerated, but must be adapted to the acute or chronic pattern, with tetracyclines and doxycycline being considered the mainstay of antibiotic therapy 2, 3, 5.
• Vaccination of animals in infected flocks, as well as in uninfected ones close to them, with an efficient vaccine can prevent abortions and shedding of the bacteria 2.
• Several measures should be undertaken to minimize exposure among people working with animals or handling birth products, and hygienic precautions should be put in place during an outbreak to lessen the spread of disease to animals 3, 4.