What is Cattlemen's disease, also known as Q (Query) fever?

What is Cattleman's Disease (Q Fever)?

Cattleman's disease, also known as Q fever, is a zoonotic bacterial infection caused by Coxiella burnetii that primarily affects people with occupational or residential exposure to livestock, transmitted mainly through inhalation of contaminated aerosols from animal birth products, and presents as either an acute febrile illness (often with pneumonia or hepatitis) or a rare but potentially fatal chronic form characterized by endocarditis. 1

The Causative Organism

• Coxiella burnetii is an obligate intracellular, gram-negative bacterium that is extremely resistant to heat, desiccation, and environmental stresses 1
• The organism can survive in the environment for months to years and becomes airborne, traveling on wind currents for miles 1
• It exhibits "antigenic phase variation" with different lipopolysaccharide complexities that distinguish acute (phase II antibodies) from chronic infection (phase I antibodies) 1, 2

Transmission and Risk Factors

The primary route of transmission is inhalation of aerosols from contaminated soil, animal waste, or birth fluids from infected livestock, particularly cattle, sheep, and goats. 1

High-Risk Populations

• Occupational groups: veterinarians, farmers, slaughterhouse workers, butchers, and laboratory personnel handling C. burnetii 1
• Geographic risk: living within 10 miles of farms housing livestock, even without direct animal contact 1
• Demographic factors: males have higher symptomatic illness rates, and persons aged 60-64 years have the highest age-related risk 1

Important Epidemiologic Context

• Direct animal contact is NOT required for infection—airborne transmission can occur over distances up to 10 miles from infected farms 1
• 60% of reported U.S. cases occur in patients who do not report livestock contact 1
• Cases peak in spring, correlating with livestock birthing seasons 1

Clinical Presentations

Acute Q Fever

Approximately 50% of infected persons develop symptomatic acute disease after a 2-3 week incubation period, characterized by nonspecific febrile illness, often with pneumonia or hepatitis. 1

Cardinal Symptoms

• Fever (median duration 10 days untreated), fatigue, chills, and myalgia are the most frequently reported symptoms 1, 3
• Severe, debilitating retroorbital headaches with photophobia are common and may be misdiagnosed as migraines or meningitis 1, 3
• Nonproductive cough occurs in approximately 50% of pneumonia cases 3
• Prolonged fever (>10 days) with normal leukocyte count, thrombocytopenia, and elevated liver enzymes is highly suggestive 1

Clinical Manifestations

• Pneumonia and hepatitis are the most common organ-specific presentations 1
• Mortality rate is low (<2%) in acute disease 1
• Up to 60% of infections are asymptomatic but result in seroconversion 1

Chronic Q Fever

Chronic Q fever develops in <5% of acute infections, typically manifesting as endocarditis in patients with preexisting valvular or vascular defects, and is always fatal if untreated. 1

High-Risk Groups for Chronic Disease

• Patients with valvular heart disease or prosthetic valves 1
• Persons with vascular grafts or arterial aneurysms 1
• Immunosuppressed individuals 1
• Pregnant women 1

Diagnostic Challenges

• Routine blood cultures are negative 1
• Vegetative lesions are visualized by echocardiography in only 12% of patients 1
• Diagnosis requires rising phase I IgG titers 1

Diagnosis

Serologic testing showing a fourfold change in IgG antibody titer to C. burnetii phase II antigen by immunofluorescence assay (IFA) in paired serum samples is the diagnostic standard for acute Q fever. 3

Diagnostic Criteria

• Single IgG titer ≥1:128 to phase II antigen in a patient ill >1 week indicates probable acute infection 3
• PCR on whole blood or serum during the first 2 weeks of symptoms can provide early diagnosis 3
• Chronic infection is characterized by rising phase I IgG titers 1

Treatment

Doxycycline is the treatment of choice for Q fever at all ages and should be initiated immediately when Q fever is strongly suspected, without waiting for laboratory confirmation. 3, 4

Acute Q Fever Treatment

• Doxycycline should be started within the first 3 days of symptoms for maximum effectiveness 3
• Treatment within 24 hours of fever onset is extremely effective in shortening illness duration and reducing symptom severity 1
• The FDA approves doxycycline for Q fever treatment 4
• Fever typically resolves within 72 hours of appropriate treatment 5

Chronic Q Fever Treatment

• Combination therapy with doxycycline and hydroxychloroquine is used long-term 6, 2
• Early treatment in chronic disease may be lifesaving 1

Common Pitfalls

• Failing to consider Q fever in patients without direct animal contact—airborne transmission can occur miles from the source 1
• Misdiagnosing severe headaches as migraines, meningitis, or dental problems rather than Q fever 1
• Delaying treatment while awaiting serologic confirmation in clinically compatible cases 3
• Missing chronic Q fever risk in patients with valvular disease or vascular abnormalities who had previous acute infection 1
• Assuming negative blood cultures rule out endocarditis in at-risk patients 1

Prevention

• No licensed vaccine is available in the United States 1
• Occupational settings should implement engineering controls, administrative controls, and personal protective equipment 1
• Pasteurization of milk prevents transmission through dairy products 6
• Standard precautions are sufficient for healthcare providers during routine care 1