Q Fever as a Cause of Fever of Unknown Origin and Thrombocytosis: First Molecular Evidence of Coxiella burnetii in Brazil

Q fever is a worldwide zoonosis caused by Coxiella burnetii, a small obligate intracellular Gram-negative bacterium of the order Legionellales. The disease has a broad spectrum of clinical manifestations, ranging from a limited febrile illness, pneumonia, and hepatitis to life-threatening forms such as endocarditis and meningoencephalitis (Tissot-Dupont and Raoult 2008, Cunha et al. 2009). Ticks, farm animals, pets, and many wild animals are possible reservoirs of infection. Transmission to humans is usually via inhalation of contaminated aerosols from urine, feces, milk, and birth products or less commonly by ingestion of unpasteurized milk from infected farm animals. Occupational groups such as veterinarians, farmers, and slaughterhouse workers are at highest risk. Although Q fever is distributed throughout the world, its distribution in Brazil, where it is not a reportable disease, is poorly defined.

Since the first seroepidemiologic study was published in 1953, little additional information has become available and only four cases associated with endocarditis have been confirmed by serology or Gimenez staining of valves (Brandão et al. 1953, Travassos et al. 1954, Ribeiro do Valle et al. 1955, Riemann et al. 1974, Costa et al. 2006, Siciliano et al. 2008, Lamas et al. 2009).

On October 13, 2008, a 47-year-old man from Itaboraí, state of Rio de Janeiro, in southeastern Brazil, was admitted to the Gaffrée Guinle University Hospital/UNIRIO with a fever of >40 days duration, associated with abdominal pain, headache, nausea, fatigue, malaise, and depression. Physical examination was unremarkable, except for abdominal pain on palpation.

Laboratory exams revealed a high erythrocyte sedimentation rate (82 mm in the first hour), leukocytosis (13,100/mm³) with neutrophilia (74%), and thrombocytosis (611,000/mm³). Bone marrow aspiration showed slight hyperplasia of the monocyte–macrophage system and granulocytic cells. Echocardiogram and tomographic scans of the abdomen and thorax were normal. Treatment with a fourth-generation cephalosporin (cefepime 4 g/day) was begun, but without improvement.

The patient reported that 3 months before falling ill he had purchased 12 goats (Saneen breed), some of them for personal milk supply and some to sell to the community. The goats were kept together with other animals, 14 dogs and 2 cats. Additionally, the patient had a history of contact with the birth products of three goats that had aborted, 3 weeks before the onset of the symptoms.

Because of a high clinical suspicion of brucellosis, treatment with doxycycline (200 mg/day) and rifampin (600 mg/day) was begun and the fever disappeared in 4 days.

Serological testing for brucellosis, toxoplasmosis, leishmaniasis, cytomegalovirus, hepatitis B and C, syphilis, bartonellosis, ehrlichiosis, rickettsiosis, and histoplasmosis and detection of circulating capsular polysaccharide antigen from Cryptococcus neoformans performed on the first available serum sample collected on 40th day after onset of illness were negative. Mycobacteria, leishmania, and fungi cultures were also negative. Two serum samples collected 40 and 70 days after onset of the illness were tested for C. burnetii using a commercial indirect immunofluorescence assay for IgG (Panbio). Titers of specific antibodies to phase II antigen of 256 and 1024 were detected in the first and second serum samples, respectively. After DNA extraction using a commercial kit (QIAamp DNA; Qiagen), polymerase chain reaction (PCR) was performed and heat shock proteins genes (htpAB) of C. burnetii (687 bp) were amplified from the first serum sample DNA (Hoover et al. 1992). The PCR was repeated without a positive control and the result was confirmed, but DNA sequencing of the amplicon detected was not possible because of insufficient serum samples (Fig. 1). Rifampin was discontinued and the patient was treated with doxycycline for 21 days.

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FIG. 1.

Agarose gel electrophoresis of Coxiella burnetii polymerase chain reaction product amplified from total DNA of serum sample. S, sample from the patient with Q fever; M, molecular size markers (100-bp ladder); N, negative control. The arrow indicates the amplification of a 687-bp htpAB fragment.

In December 2008, a field investigation was carried out in the patient's home and blood samples from his family (wife and daughter) and 13 dogs were collected for analysis. His wife, who handled and fed them goat milk, told the investigators that one of their dogs (a 7-month-old female) had died, and another had aborted puppies, while the patient was in hospital. The wife was seroreactive for C. burnetti (titer of anti-phase II IgG of 128) and 2 of the 13 dogs showed indirect immunofluorescence assay (IFA) reactivity (titers of anti-phase II IgG of 64 and 128) but displayed no clinical manifestations. Unfortunately, the goats had been sold to another farmer so biological samples from these animals were not available for analysis.

All the symptoms were resolved and the patient was discharged at 4 weeks after admission. A third sample of the patient's serum collected at 6 months after the onset of illness was analyzed and showed an IgG titer of 128 against phase II antigens of C. burnetii.

Although several classical clinical descriptions of Q fever have been recognized in different regions of the world, some atypical and severe forms can be difficult to identify. Fever of unknown origin, clinical pictures mimicking systemic inflammatory disease, or lymphoproliferative disorders have also been described (Tissot-Dupont and Raoult 2008, Cunha et al. 2009). This article reports a case of Q fever presenting as fever of unknown origin and thrombocytosis that recovered after 3 weeks of treatment with doxycycline. Although thrombocytopenia occurs in about 25% of patients in the early phase of the illness, the presence of reactive thrombocytosis has also been described during its later phase (Tissot-Dupont and Raoult 2008, Cunha et al. 2009).

Studies of C. burnetii in humans and animals are frequently based on serologic tests, and the prevalence of C. burnetii infection varies widely from one country to another (Tissot-Dupont and Raoult 2008). Our findings provide definitive confirmation of Q fever in Brazil, where there are no molecular studies documenting C. burnetii infection in humans or animals. Anti-C. burnetii antibodies were also detected in the patient's wife and in two dogs, providing further evidence of the circulation of C. burnetii in Itaboraí, Rio de Janeiro, Brazil.

Although the PCR results were positive, DNA sequencing of the detected amplicon was not possible because of lack of sufficient biological material in the first serum sample.

Further studies including molecular characterization of C. burnetii are necessary to establish the extent and the importance of Q fever in Brazil.