Identifying the cause of respiratory infection

A case with symptoms typical of a URTI turned out to be caused by a zoonotic infection.

Transmission electron micrograph showing Coxiella burnetii (Photograph: SPL)
Transmission electron micrograph showing Coxiella burnetii (Photograph: SPL)

A 37-year-old woman presented with a seven-day history of illness. Initially the patient had a high temperature for two days and felt feverish, with aching in her neck, shoulders and legs.

After a general improvement in her condition, she had then felt a little breathless, with a dry cough, a mildly sore throat and a blocked nose for two days prior to the consultation.

This history seemed to be of a typical URTI and I was therefore surprised to find a number of fine crepitations in her right lung base. At the time of presentation she was apyrexial and had a dry cough.

Initial investigations
These findings seemed to be out of proportion to her symptoms, and I wondered whether the diagnosis might be some form of atypical pneumonia. I initially treated her with a high dose of clarithromycin 500mg twice daily, and arranged for a chest X-ray and blood tests.

Her chest X-ray showed an ill-defined patchy, round opacity in the right costophrenic region. CRP was mildly raised at 44mg/L and ESR also mildly raised at 38mm/hr.

Upon review a week later, the patient felt a little better and her temperature was 36.8oC. Chest auscultation showed a definite reduction in the crepitations in the right base but still some present in the right axilla.

On further enquiry, she admitted that she had recently visited a friend's farm and helped deliver a stillborn calf. With this history I thought about Q (which stands for Query) fever. I telephoned the local microbiologist to arrange for appropriate serology.

The microbiologist also suggested checking urine for pneumococcal and legionella antigens. I started the patient's treatment with doxycycline 100mg twice daily, initially as a two-week course.

Serology showed no evidence of pneumococcal or legionella infection but titres against Q fever (Coxiella burnetii) were positive. This triggered a number of discussions with our local microbiology department and also the Health Protection Agency (HPA), which sent over guidelines on the management of Q fever.

The main reservoirs for Q fever are arthropods and farm animals, such as cattle, and this diagnosis should be considered in unusual cases of pneumonia related to such contact.

A further week of doxycycline was prescribed, making three weeks' treatment in total. The patient's clinical course has been one of continual improvement, although it took four weeks before she was fit enough to return to work, initially on a part-time basis. Her CRP and ESR returned to normal.

It was also felt that endocarditis should be ruled out. Repeated auscultation and searching for splinter haemorrhages, and repeating her inflammatory markers all showed no evidence of this. I performed an echocardiogram, which showed no signs of endocarditis.

Guidelines on Q fever
The HPA guidelines indicate that while Q fever has a lower mortality rate than other atypical pneumonias, a significant proportion of patients go on to develop chronic Q fever and this typically involves endocarditis in 60-70% of cases. This can occur from one month to several years later, even when appropriate treatment has been given in the first instance.

Initial diagnosis is often only picked up some weeks after the patient contracts the illness and this may be a factor in developing chronicity. Chest X-ray typically shows single or multiple opacities, most commonly in the lower lobes.

Hepatitis is common; it is usually mild but rarely, can be severe. Neurological symptoms occur in up to 22% of acute cases, most commonly meningitis, meningoencephalitis or myelitis.

The patient is now very well and her inflammatory markers are normal. A second set of serology is being reviewed by the HPA, which is comparing paired titres to look for evidence of recovery rather than chronicity.

However, we will need to remain vigilant with any illness that she might develop and consider the possibility of chronic Q fever.

  • Dr Cotterell is a GP in Thrapston, Northants

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