Comments
INITIAL SYMPTOMS:
Asymptomatic in up to 60% of cases; [ABX Guide] Flu-like illness with headache & nonproductive cough; Other syndromes are pneumonia, hepatitis (usually following ingestion of contaminated milk), encephalitis, & endocarditis; [PPID, p. 3272]
FINDINGS:
About 60% of cases in the USA are manifest as hepatitis. The three types of hepatitis are acute hepatitis, persistent fever associated with granulomas of the liver, and incidental hepatitis in patients with pneumonia. Pneumonia may be atypical, rapidly progressive, or incidental. Of patients with lung infiltrates by chest x-ray, only 28% have a cough. Other findings of patients with Q fever pneumonia are headache (75%), sweats (84%), myalgia (68%), nausea (49%), pleural effusions (35%), leukocytosis (33%), pleuritic chest pain (28%), diarrhea (21%), and splenomegaly (5%). Almost all patients with pneumonia have slight elevation of liver enzymes (2-3 times). Thrombocytopenia may occur. [PPID, p. 2210] "Unlike rickettsial diseases, acute Q fever does not cause a rash." [Merck Manual, p. 1287] A nonspecific rash occurs in 4-18% of cases. Patients with endocarditis may have hepatomegaly, splenomegaly, purpuric rash, increased gamma-globulin, renal insufficiency, stroke, and heart failure. [Harrison ID, p. 738]
COMPLICATIONS:
Chronic disease (culture negative endocarditis often without fever) may be difficult to diagnose. Rare complications are pericarditis, myocarditis, meningitis, encephalitis, osteomyelitis, and chronic fatigue (debated). [ABX Guide: Coxiella burnettii] About 1% of Q fever cases are complicated by meningoencephalitis, which may be accompanied by meningismus, cranial nerve palsies, seizures, and coma. Other possible complications are osteomyelitis, hemolytic anemia, optic neuritis, and erythema nodosum. [PPID, p. 2215] Complications of chronic endocarditis include cerebral emboli, renal insufficiency, splenomegaly, and hepatomegaly. [Cecil, p. 1963] Coxiella burnettii can cause uveitis. [Guerrant, p. 1005]
EPIDEMIOLOGY:
Q fever is an occupational hazard for farmers, veterinarians, and abattoir workers. "Infected animals are often asymptomatic but shed massive numbers of organisms in placental tissues and birth fluids at parturition." Infectious airborne particles may be present in straw, wool, and laundry or carried downwind a kilometer or more. The case-mortality rate is <1% in untreated cases. The primary reservoirs are sheep, cattle, and goats; also cats, dogs, birds, wild mammals, and ticks. Some cases may be transmitted by raw milk from infected cows or goats. [CCDM, p. 493-7] The organism has a spore form that can survive on meat in cold storage for 1 month and in infected tissue stored in formaldehyde for 4-5 months. There are case reports of infections transmitted by handling contaminated laundry or living next to a road used by farm vehicles hauling contaminated dust and straw. Other animals that carry the infection are horses, pigs, and rabbits. [PPID, 2208-9] Person-to-person transmission has been reported (sexual, transfusion, and during delivery). A vaccine is available in Australia. [Cecil, p. 1963]
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