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Q Fever Facts

We recently diagnosed Q Fever as the confirmed cause of placentitis resulting in still birth in dairy calves. We also have had 2 further cases in aborted lambs where Coxiella burnetii has been demonstrated in both smear examinations and by PCR. This is an unusual diagnosis locally and since we are approaching the peak lambing/calving period a quick refresher is opportune.

  • Q fever is caused by the gram negative intracellular bacteria Coxiella burnetii.
  • Most infections in livestock are asymptomatic however it can cause late abortions and still births in cattle, sheep and goats.
  • It is considered endemic in UK dairy herds with 70% of 155 bulk tank samples testing PCR positive for C. burnetii.
  • The organism is shed in milk, urine, faeces, and in particularly large numbers around abortion/parturition when recrudescence of latent infection can occur.
  • C. burnetii survives as spores in the environment for many months and is resistant to drying, heat and most disinfectants. It is killed by pasteurisation. Windborne spread and ticks are other possible sources of human infection.
  • Q fever is zoonotic via inhalation of the spores on contaminated dust particles or through skin abrasions. Most infections are asymptomatic but it can cause fever, headache, malaise and more serious disease such as pneumonia, hepatitis, meningitis or endocarditis.
  • Q fever infected placentas can look similar to EAE and the organism is detectable on routine MZN smears. As it is an environmental organism, and can be shed by latently infected animals, this does not prove causality. Any positive smears are followed up with PCR testing, histopathology and immunohistochemistry.
  • The genotype of C. burnetii can determine the likelihood of zoonotic spread. Dairy goats were thought to be the source of a Q Fever epidemic in the Netherlands. Over a 4 year period almost 4,000 human cases were reported and abortion storms affecting up to 80% of goats occurred on infected farms. We are looking into getting our isolates genotyped.
  • The most recent data we could find on human infections in the UK was from 2013 when 44 cases of Q fever were confirmed in humans by laboratory diagnosis in England and Wales, with only 2 confirmed cases in Scotland.
  • A study reported in 2008 in Northern Ireland demonstrated that 12.8% of the general population were seropositive for Coxiella burnetii. 48.8% of the farmers within the survey population were seropositive for Coxiella burnetii. Thankfully infection and antibody production in many cases is asymptomatic.

References

Valergakis et al. (2012) Coxiella burnetii in bulk tank milk of dairy cattle in south-west England. Veterinary Record, 171, 156-157

Q Fever: Information for farmers. PHE publications gateway number 2015500.

http://www.gov.uk/government/uploads/system/uploads/attachment_data/file/487806/Q_fever_information_for_farmers_2015.pdf

Roest et al. (2011) Molecular epidemiology of Coxiella burnetii from ruminant in Q Fever outbreak, the Netherlands. Emerging Infectious Diseases, 17(4), 668-675

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