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Q fever

Queensland Health Guidelines for Public Health Units

Revision History

 Version  Date  Changes
 1.0 November 2010  Full revision of guideline. 

Infectious Agent

The infectious agent is Coxiella burnetii, an obligate intracellular Gram negative bacterium. 

Notification Criteria

Clinical Evidence

A clinically compatible disease.

(NB. clinical evidence is required for reporting to NOCS in the absence of definitive laboratory evidence but does not by itself constitute a requirement for clinicians to notify).

Laboratory definitive evidence

Seroconversion or fourfold or greater increase in antibody level to Phase II or Phase I antigens in paired sera tested in parallel (Phase 1 not in national case definition)
OR
detection of Coxiella burnetii by nucleic acid testing
OR
isolation of C. burnetii from a clinical sample (note this practice should be strongly discouraged except where appropriate facilities and training exist).

Laboratory suggestive evidence

Detection of C. burnetii specific IgM (at least 1/160 by IF)
OR
demonstration of a raised serum complement fixation antibody titre (>=1/64) to phase II
antigen of C. burnetii (not in national case definition).

Community outbreak criteria

Two or more epidemiologically linked cases.

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Notification Procedure

Pathology Laboratories

To notify on laboratory definitive or suggestive evidence by usual means.

Laboratory Aspects

Clotted blood is required for serology. Two samples should be collected if Q fever is suspected – one at presentation, and another 1 - 4 weeks later. If acute Q fever is suspected and the patient presents within ten days of illness onset, the second sample should be taken around day 12 - 20. If the patient presents late, or Q fever isn’t suspected within ten days of symptom onset, the second sample should be taken 5 - 7 days after the first. Significant titres may take 3 - 4 weeks from illness onset to appear, so a third sample should be taken three or four weeks after fever onset where the second sample was taken before three weeks. Antibodies to Phase II antigens are high in the acute illness and antibodies to Phase I are high in chronic disease.

Acute Q fever

The organism may be detected in blood up to day 10 after illness onset. If the patient presents within ten days, unclotted blood (EDTA tube) is required for PCR and possible culture.

Chronic Q fever

C burnetii DNA may be detected by PCR in peripheral blood mononuclear cells or in biopsy specimens from granulomatous tissue.

Reporting to NOCS

Report only confirmed cases.

Confirmed case: A confirmed case requires either

1. Laboratory definitive evidence

or

2. Laboratory suggestive evidence and clinical evidence.

NB: Although it is unusual to get high titres after Q fever vaccination, recent immunisation should be excluded as an explanation of serological evidence.

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Public Health Significance and Occurrence

Q fever is a zoonotic disease that occurs around the world. The incidence is greater than that reported because of subclinical infection and limited clinical suspicion and testing. In Australia, the disease is particularly likely to affect meat workers, veterinarians, those working on farms, and those in contact with native animals such as kangaroos. Farm workers are a group particularly likely to be underdiagnosed as they often live at a distance from health services and see little need to have a blood test when they are well, yet serology is often inconclusive until symptoms have resolved. Notification rates in Australia generally reflect the intensity of local cattle, sheep and goat husbandry and associated processing industries. Prior to the National Q Fever Management Program, there were around 500 – 800 cases annually. Q fever notifications and compensation claims have reduced substantially since this program, with 369 and 308 notified cases in Australia in 2008 and 2009 respectively. The incidence remains highest in northwest NSW and southwest/central west QLD. There were 130 notifications of Q fever in Queensland in 2009.

Clinical Features

Reported clinical symptoms vary by country. It is estimated that 60% of cases in adults are asymptomatic. In Australia, acute Q fever most commonly presents as an influenza-like illness with varying degrees of pneumonia and hepatitis.  Fever is not always present.
The case fatality rate is 1-2%. Myocarditis is rare but is one of the more common causes of death. If untreated, the acute illness lasts 2-6 weeks and may be accompanied by substantial weight loss. Despite rapid resolution of the acute illness, return to full health may be slow in many patients. Post Q fever fatigue syndrome, with systemic symptoms that fail to recover more than 12 months after the acute illness, is the most common chronic sequela following acute infection, occurring in 10-20% of notified cases. Chronic disease can occur a month or years after acute illness and sometimes there is no history of acute illness.  Endocarditis accounts for 60-70% of chronic Q fever and nearly always occurs in patients with underlying immunosuppression or cardiac valve abnormalities.

Continuing or recrudescent granulomatous infection may also occur in bone, joints, liver, lung, testes and soft tissues. In children chronic infection may also present as osteomyelitis. Primary infection or recrudescence in pregnancy can lead to abortion, premature birth or neonatal death. 

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Reservoir

A wide variety of animals can be infected with C. burnetii including domesticated animals  such as  cattle, sheep, goats, dogs and cats; non human primates; wild rodents and small mammals; big game wildlife; and non mammalian animals including reptiles, amphibians, birds (domesticated and wild), fish and many ticks.

Mode of Transmission

  • In Australia, cattle, sheep and goats are the main sources of human infection. Most Q fever infections result from inhalation of infectious aerosol particles from parturient or slaughtered animals. The highest risks are associated with birthing and the evisceration part of butchering.
  • Occupational exposure through contact with animal products (hides and wool) is also a risk.  Bacteria are concentrated in tick faeces which contaminate hides and wool.
  • Consuming unpasteurised milk can lead to disease.
  • Inhalation of dust is important as environmental contamination from parturient and slaughtered animals may last for months or years.
  • Contact with contaminated clothing can lead to disease.
  • Windborne spread is well recognised and the organism can travel several km. People can be infected from trucks carrying cattle, sheep or contaminated straw.
  • Person to person transmission is very rare but can occur through:
    • blood or marrow transfusion
    • vertical or perinatal transmission
    • autopsy of infected cadavers
    • sexual transmission
  • Meat workers who exclusively work with pigs and town butchers who receive dressed carcasses (ie. eviscerated and skinned) do not appear to be at occupational risk.

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Incubation Period

Commonly 2 - 3 weeks, depending on the size of the infecting dose (range 4 days to 6 weeks).

Period of Communicability

Person to person spread rarely occurs. Contaminated clothing may be a source of infection. Animals are most infectious when pregnant or birthing.

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Susceptibility and Resistance

  • Infection usually confers life-long immunity.
  • Of workers with prolonged exposure (eg. abattoir workers who have worked for over 10 years), 50% will be immune through clinical or subclinical infection.
  • Antibodies detected by CF persist for 3-5 years; antibodies detected by IF may persist as long as 10 - 15 years. The skin test usually remains positive for much longer than antibody tests.
  • Vaccination is very effective in preventing Q fever (close to 100%). Lack of seroconversion after vaccination is not a reliable marker of lack of immunity. The duration of protective immunity following immunisation is unknown, but is believed to be in excess of 5 years.
  • Vaccination during the incubation period does not prevent the development of disease.

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Management

Cases

Investigation
In the situation of a presumptive case, contact the treating medical practitioner in an attempt to confirm the diagnosis by ascertaining the presence of clinically compatible illness and/or obtaining a second specimen for further serological testing.  In consultation with the case and treating medical practitioner, attempt to identify the source of infection eg. exposure to animals.  If the likely source of infection is the case’s workplace, consider informing Workplace Health and Safety Queensland.
 
Counselling
The case should be advised of the nature of the infection and its mode of transmission, and of appropriate precautions necessary to prevent others from becoming infected from the same source:

  • vaccination as appropriate for contacts
  • disinfection – hands and arms should be washed thoroughly in soapy water after handling animals or carcasses
  • yard facilities for sheep, goats and cattle should be sited well away from domestic living areas
  • personal protective equipment and contaminated clothing should be removed prior to returning to the home environment
  • care should be taken to properly dispose of animal products of conception.  This usually involves burial under a half to one metre of soil or incineration
  • milk should be pasteurised.

Treatment
Refer to latest edition of Therapeutic Guidelines: Antibiotic. A two week course of doxycycline is generally used to treat acute Q fever. Cotrimoxazole can be used in children aged eight years or less and is recommended for pregnant women until delivery, even if recovered, to prevent foetal and maternal complications. In chronic disease or endocarditis, prolonged combination therapy (with addition of rifampicin or hydroxychloroquine) and cardiac surgery may be required. Expert advice eg. from an infectious diseases physician should be sought as appropriate.

Contacts

Definition 
Any person who may have experienced the same exposure as the case or who may have been exposed to contaminated items associated with the case (eg. clothing, transport). Person-to-person transmission is extremely unlikely.
 
Investigation 
Enquire about other possible cases or others with similar exposure in the home and workplace.

Management
Emphasise preventive measures such as those listed above under case management. Recommend vaccination where appropriate (see below).

Community outbreaks

Investigate to identify the likely source of infection.  Identify any other linked cases. Liaise with Workplace Health and Safety Queensland regarding prevention strategies if the outbreak is workplace related.  Provide information on vaccination and other preventive measures for any defined community population identified to be at risk.

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Preventive Measures

Infection control measures as listed above under case management. Q fever vaccination is recommended for those at risk of infection – see current edition of The Australian Immunisation Handbook for recommendations. Workplace health and safety legislation obliges employers to protect exposed workers from preventable disease. New recruits are especially at risk. Ideally, vaccination should occur at least 15 days before the person starts working in an at-risk environment.

Pre-vaccination testing is imperative as a severe reaction can occur if those already immune are vaccinated. A stringent pre-vaccination protocol must be followed, which includes skin testing for cellular immunity, serological testing for humoral immunity, and a detailed history looking for previous disease compatible with Q fever, previous vaccination and occupational/other exposures. Pre-vaccination screening tests require expertise in both administration and interpretation. Expert advice should be sought where the risk of Q fever is high and serology is positive with a negative skin test.

The lower age limit for Q fever vaccination is not known. However, it is not currently recommended for use in anyone aged less than 15 years. Q fever vaccination is not recommended during pregnancy. In general, Q fever testing and vaccination should be avoided in individuals with impaired immunity – if exposure is unavoidable, expert advice on vaccination should be sought.

The National Q Fever Management Program sponsored by the Australian government operated from 2001 to 2006. Free vaccinations were provided first to meatworkers and shearers, then later to farmers, their families and employees in the livestock-rearing industry. While the program has now ceased, the national Q fever register is still in operation and can be accessed at: www.qfever.org. This website has a link to lists of accredited Q fever vaccine service providers and a searchable database of the immune status of workers who choose to submit their details.

Q fever vaccine is available from the Commonwealth Serum Laboratories, phone (07) 3849 6140.

Town planning should consider the potential for windborne spread of Q fever and limit the encroachment of residential dwellings on existing likely sources of Q fever including abattoirs, tanneries, and stockyards. The recommended buffer zone between residential dwellings and these types of facilities is at least 1km.

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Summary

Complete case report form for local unit file and fax to the Communicable Diseases Branch, Queensland Health, on request.

References

Australian Department of Health and Ageing. 2008. The Australian Immunisation Handbook (9th ed). Australian Government: Canberra.

CSL Biotherapies. 2009. A guide to Q fever and Q fever vaccination. CSL Biotherapies: Melbourne, Australia.

Cutler SJ, Bouzid M, Cutler RR. 2007. Review: Q fever. J Infect, 54: 313 – 318.

Heymann D. (Ed). 2008. Control of Communicable Diseases Manual (19th ed). American Public Health Association: Washington.

Maltezou HC, Raoult D. 2002. Q fever in children. Lancet Infect Dis, 2: 686 – 691.

Parker NR, Barralet JH, Bell AM. 2006. Q fever. Lancet, 367: 679 – 687.

Therapeutic Guidelines: Antibiotic.  2010. Melbourne: Therapeutic Guidelines Limited. Accessed online 4 November 2010.


Last updated: 8 December 2010