Steven Graves shows how big a problem Q fever has become in the Netherlands
[plenary lecture; notes by the MicroGnome]
In 2007 over 180 new cases of Q fever were detected in the Netherlands. The annual total of cases rose during the following two years to over 2000 cases and there were almost 200 in the first two months of 2010. As most of these infections occurred during the summer months, a significant rise is expected during the European summer this year.
This series of cases constitutes the single largest outbreak of Q fever in the world so far. It has been concentrated in southern Holland and associated with goat farms where goat’s milk is produced for cheese manufacture. In some communities the incidence is as high as 1 in 200.
The first unusual observation was an increase in miscarriages in goats during 2005. The first increase in human cases occurred in 2007, but it was 2008 before a human epidemic had been properly recognised. Vaccination of goats was introduced, at first on a voluntary basis, then in 2009 it was made compulsory. Unfortunately, vaccination does not eliminate the infection from goats. Other control measures now in use include euthanasing all pregnant goats, bulk milk testing by nucleic acid amplification (PCR), composting of goat manure.
Clinical features are normally fever with headache, and around 50% progress to features of pneumonia. 3.5% have gone on to develop hepatitis (as compared with 20% in NSW). 80% vets are seropositive. A high C-reactive protein was useful as a non-specific indicator of Coxiella infection in acute cases in the Dutch outbreak.
Q fever (‘query fever) was first described by Derrick in 1937 following an investigation into an unusual infection of meat workers in Brisbane. The differential diagnoses included typhus, typhoid fever and leptospirosis but this was recognised as something new and different. Derrick was assisted by MacFarlane-Burnet, who successfully isolated the infective agent, now known as Coxiella burnetii, in 1937. A year later David & Cox isolated a similar organism from a tick in Montana, USA. The principal animal species associated with Q fever are cattle, goats, and sheep, kangaroos and bandicoots. The disease is widely distributed around the world, with New Zealand being the only Q fever free country. Its main concentration in Australia is in Southeast QLD and Northern NSW. A recognised host is the kangaroo tick, Amblyomma triguttatum though its role in human infection is unclear. Most human infections result from the inhalation of airborne animal products. The disease is notifiable but underdiagnosed.
Diagnosis is by a combination of
- recognition of the possibility by the attending physician
- nucleic acid amplification test (PCR) in the first week of acute illness
- serological methods in the later stages of acute disease and during chronic illness: MIF, EIA, CFT
The infection is notifiable but clearly under-diagnosed.
