Mystery bug proves tough to defeat

PUBLISHED : Tuesday, 18 October, 2011, 12:00am
UPDATED : Tuesday, 18 October, 2011, 12:00am


Electrical technician Chan Man-ching had a history of good health, until a persistent two-week fever forced the Macau resident to check himself into a hospital in the former Portuguese enclave.

On examination, doctors found that Chan (name changed for patient confidentiality reasons), a 52-year-old father of two, had a swinging fever, an enlarged liver and inflammation of the iris - the coloured part of the eye - and the ciliary body, which comprises the muscles and tissues that make fluid in the eye. A succession of blood tests showed that he had progressive anaemia, a raised white blood cell count, abnormal liver function and his blood was slow to clot.

Chan was extensively examined to determine the underlying cause of his fever. Tumour marker levels were found to be normal, no bacterial or fungal growth was detected in the blood, urine, stool or cerebrospinal fluid cultures, and other investigations for viral infections all came back within normal ranges. However, a liver scan suggested hepatitis, since the liver was swollen, enlarged and inflamed. In the meantime, the fever persisted despite Chan being given two successive courses of intravenous antibiotics every eight hours for 13 days.

After his condition failed to improve despite being in the hospital for 17 days, Chan was transferred to Queen Mary Hospital in Hong Kong. A liver biopsy revealed multiple doughnut-shaped granulomas (small areas of inflammation due to tissue injury), and a cardiac ultrasound showed that some of the fibrous strings that control the movement of one of the heart valves had ruptured.

Further, an elevated level of antibodies due to bacteria called Coxiella burnetii was detected in two sets of blood samples taken two weeks apart.

With these findings, Chan was diagnosed with chronic Q fever. The 'Q' stands for 'query: the name was coined when little was known about what caused the fever. It was first described in slaughterhouse workers in Brisbane, Australia. Q fever is common in parts of Australia, North America and Europe, but is seldom seen in Hong Kong.

Q fever can cause acute or chronic illness in humans, who usually pick up the condition after coming into contact with infected animals or being exposed to a contaminated environment. Cattle, sheep and goats are commonly infected with C. burnetii, which gets excreted in the milk, urine and faeces of infected animals. The bacteria is extremely robust and is resistant to common disinfectants, heat or dehydration, which means it can survive for long periods in infected environments.

Humans are thought to be very susceptible to Q fever and only a small number of bacteria is needed to cause infection. It's likely that Chan became infected with C. burnetii after cleaning up bird droppings while repairing outdoor electrical wires four to six months prior to his hospital admission.

Chan was treated with two different oral antibiotics: doxycycline twice a day and hydroxychloroquine three times a day. His condition improved over the next week, with the fever, liver malfunction, blood clotting response and iris inflammation all subsiding. Chan has to continue taking the antibiotics for at least 18 months, depending on how his blood serum responds, and must have regular follow-ups at an outpatient clinic.

University of Hong Kong researchers, in a report in the Hong Kong Medical Journal, believe that the incidence of Q fever, both in its acute and chronic forms, have been underestimated in Hong Kong. This is due to a number of reasons, including geographical uniqueness, clinical bias, diagnostic difficulty and suboptimal surveillance.

Dr Jasper Chan Fuk-woo, attending physician and honorary assistant professor of HKU's department of microbiology, says: 'The incidence of Q fever seems low in Hong Kong. It is often under-diagnosed because most patients with acute fever present with a self-limiting illness and are misdiagnosed as having influenza.

'Only 3 to 5 per cent of affected individuals [like Chan] progress to the chronic form. Diagnosis is often missed if an antibiotic like doxycycline is used [to treat] atypical bacterial infections.'