What is Q fever and how is it caught?

Q fever is caused by the bacterium Coxiella burnetii, which infects cattle, sheep, goats, kangaroos, and other animals. Humans are infected primarily by inhaling contaminated aerosols — dried birth fluids, placenta, faeces, or wool dust — rather than by direct animal contact. The organism is extraordinarily infectious: a single organism can cause human infection. High-risk occupations include farmers, abattoir workers, shearers, veterinarians, and laboratory workers. Q fever is the most common notifiable zoonosis in Australia, with several hundred to over a thousand cases reported annually, predominantly in Queensland, New South Wales, and Victoria.

Why is the pre-vaccination test for Q-VAX so important?

Q-VAX can cause a severe localised granulomatous reaction — a painful swelling at the injection site lasting weeks — if it is given to someone who is already immune to Q fever, either from a previous infection or a previous vaccination. This reaction can be disabling and is largely preventable with screening. Before any Q-VAX vaccination, two screening tests are mandatory: a skin test (intradermal injection of diluted Q fever antigen, read at 48 hours) and a blood test for Phase I and Phase II Q fever serology. If either test is positive, vaccination is contraindicated. Never administer Q-VAX without performing and interpreting both tests first.

How is acute Q fever treated?

Acute Q fever is treated with doxycycline 100 mg twice daily for fourteen days. Treatment is most effective when started early and significantly shortens the illness duration. Doxycycline is contraindicated in pregnancy and in children under eight years — in these groups, co-trimoxazole or rifampicin are alternatives in consultation with infectious diseases. Most patients with acute Q fever recover fully with treatment. Mandatory notification to the state health department is required for every confirmed case. Serology follow-up at three and six months is recommended to detect progression to chronic Q fever.

What is chronic Q fever and who is at risk?

Chronic Q fever occurs in approximately one to five per cent of people after acute infection, almost always in people with pre-existing conditions that impair local immunity or provide a site for persistent infection. The most common form is endocarditis, affecting people with damaged or prosthetic heart valves — the infection can smoulder silently for months before diagnosis. Other forms include vascular graft infection and chronic hepatitis. Immunocompromised individuals (transplant recipients, HIV, long-term corticosteroids) and pregnant women are also at elevated risk of chronic disease. Treatment requires eighteen months or more of doxycycline combined with hydroxychloroquine, with infectious diseases oversight.

What other Australian zoonoses should GPs know about?

Leptospirosis is the second most important Australian zoonosis, transmitted through contact with water or soil contaminated with urine from infected animals — mainly cattle, pigs, dogs, and rodents. The classic presentation is flu-like with intense myalgia, headache, and conjunctival suffusion (red eyes without discharge), which is a distinctive sign. Severe leptospirosis (Weil's disease) causes jaundice, renal failure, and meningitis. Treatment is doxycycline or penicillin. Hendra virus is a rare but highly lethal paramyxovirus in eastern Australia, transmitted from flying foxes through infected horses to humans — equine handlers who develop febrile illness after contact with a sick or dead horse should be assessed as a Hendra case until proven otherwise.

Who should receive Q-VAX vaccination?

Q-VAX is recommended for people with occupational exposure to Q fever, including abattoir workers, farmers, shearers, livestock handlers, veterinarians, veterinary nurses, and laboratory workers handling Q fever specimens. It is not a routine population vaccination. The Q Fever Management Program (qfever.org) coordinates vaccination nationally. Vaccination is only effective in seronegative, skin-test-negative individuals — screening must come first. The vaccine provides long-lasting protection and is funded under the National Immunisation Program for at-risk workers, subject to state-specific arrangements.

Q fever and Australian zoonoses

Q fever and Australian zoonoses: Q-VAX, treatment, and AU general practice

By Dr HB Lo, FACRRM Reviewed 30 September 2026 13 min read

Q fever (Coxiella burnetii) is Australia's most common notifiable zoonosis — a significant occupational hazard for livestock workers, shearers, and veterinary staff. Q-VAX is the only Q fever vaccine available worldwide, developed in Australia, but requires mandatory pre-vaccination skin testing and serology: a severe granulomatous reaction occurs in previously immune individuals.

Acute Q fever is treated with doxycycline 100 mg twice daily for fourteen days. Chronic Q fever — most often endocarditis in people with valvular disease — requires doxycycline plus hydroxychloroquine for eighteen months or more under infectious diseases oversight. Every case requires mandatory notification.

Q fever is the zoonosis that defines Australian occupational medicine. It is caused by a bacterium so infectious that a single organism can establish human infection, it produces the only commercially available Q fever vaccine in the world (developed in Australia), and it has a chronic form — endocarditis — that is treatable but requires eighteen months of therapy and regular oversight to prevent relapse. Any GP practising in rural or regional Australia, or with a patient population that includes abattoir workers, livestock farmers, or veterinary staff, needs to know this condition well.

A. Core clinical — the AU general-practice framework

Q fever — aetiology and epidemiology

Coxiella burnetii is an obligate intracellular bacterium that is classified as a biosafety level 3 pathogen due to its extreme environmental stability and low infectious dose (eTG complete; Australian Immunisation Handbook). It survives desiccation for months in soil and dust.

Reservoir: cattle, sheep, and goats are the primary reservoirs in Australia. Parturition is the highest-risk event — birth fluids, placenta, and amniotic fluid contain enormous concentrations of organisms. Kangaroos, wallabies, bandicoots, and domestic pets (particularly cats that have given birth) also carry the organism.

Transmission: inhalation of contaminated aerosols — dried birth products, faeces, wool dust, or hides — is the dominant route. Direct animal contact, tick bite (uncommon in Australia), and consumption of raw milk are minor transmission pathways. Person-to-person transmission does not occur under normal circumstances.

Australian epidemiology: Q fever is the most common notifiable zoonosis in Australia, with several hundred to over one thousand cases reported annually. Queensland, New South Wales, and Victoria account for the majority of cases. High-risk occupations: abattoir and meatworks workers, livestock farmers, shearers, veterinarians and veterinary nurses, tannery workers, and laboratory staff handling clinical specimens from ruminants. Occupational health legislation in Australian states requires employers to offer Q-VAX to at-risk workers.

Clinical presentation

Acute Q fever has an incubation period of two to four weeks (range 2–6 weeks). Approximately 60 per cent of infections are subclinical or self-limiting. Symptomatic acute Q fever presents as:

Flu-like illness — abrupt onset of fever (38.5–40°C), severe headache (often retro-orbital), myalgia, and malaise; may last two to six weeks without treatment
Hepatitis — elevated transaminases with or without jaundice; granulomatous hepatitis is characteristic on liver biopsy; abnormal liver function tests are present in up to 85 per cent of symptomatic cases
Pneumonia — atypical pneumonia pattern; bilateral lower zone infiltrates; mild cough; less prominent than in Legionella; dyspnoea is unusual
Rash — macular or maculopapular rash in approximately one-third; non-specific but consistent with the diagnosis
Less common: myocarditis, pericarditis, meningitis, encephalitis, uveitis

Chronic Q fever develops in approximately one to five per cent of those with prior infection, usually months to years later (Parker NR et al, Lancet 2006). Risk factors for chronicity: pre-existing valvular heart disease or prosthetic valve, vascular grafts, immunocompromised states (HIV, organ transplantation, haematological malignancy, long-term corticosteroids), and pregnancy.

Forms of chronic Q fever:

Endocarditis — the most common and most serious form; presents with culture-negative endocarditis, low-grade fever, weight loss, and splenomegaly; vegetation may be small and missed on standard echocardiography; Phase I IgG titre ≥1:800 is highly specific for chronic Q fever per Australian Immunisation Handbook
Vascular graft infection — indolent presentation; often discovered incidentally or with fever of unknown origin
Chronic hepatitis — granulomatous hepatitis; may present with elevated transaminases alone
Post-Q fever fatigue syndrome — prolonged fatigue, cognitive difficulties, and musculoskeletal pain following acute Q fever; not strictly chronic infection; mechanism uncertain; managed with graded exercise therapy and cognitive behavioural therapy

Diagnosis

Serology is the cornerstone of diagnosis. Coxiella burnetii cannot be grown in standard laboratory culture without BSL-3 containment; PCR and immunofluorescence assays on serology are the practical tools.

Phase I and Phase II antigens: in acute Q fever, Phase II IgG and IgM antibodies rise first (Phase II = smooth lipopolysaccharide; triggers early immune response). In chronic Q fever, Phase I IgG titres become markedly elevated (Phase I = rough form; the immune system mounts a persistent response against persisting intracellular bacteria). This phase-based pattern is the key discriminator:

Acute Q fever: Phase II IgG ≥1:200 (or fourfold rise between acute and convalescent specimens)
Chronic Q fever: Phase I IgG ≥1:800

Request paired sera — acute (at time of presentation) and convalescent (2–4 weeks later) — to confirm seroconversion or fourfold titre rise.

MBS items (MBS Online): Q fever Phase I and Phase II serology is MBS-rebatable under item 69303 (complement fixation) or item 69308 (immunofluorescence assay, the preferred method). Baseline: standard consultation item 23/36/44; LFT and transaminases item 71365 range.

Mandatory notification: Q fever is a nationally notifiable condition under the National Notifiable Diseases Surveillance System (NNDSS). Notify the state or territory health department on clinical suspicion pending laboratory confirmation.

Treatment

Acute Q fever (eTG complete; AMH):

First-line: doxycycline 100 mg orally twice daily × 14 days — most effective when started within the first three days of illness; shortens fever duration from approximately fourteen days to less than three days; reduces the risk of progression to chronic disease
Pregnancy and children under 8 years: doxycycline is contraindicated; co-trimoxazole (trimethoprim-sulfamethoxazole) is the alternative in consultation with an infectious diseases physician; rifampicin may be used in certain settings
PBS listing (PBS Online): doxycycline 100 mg capsules — PBS general listing; no Authority Required for this indication

Chronic Q fever (Raoult D et al, Arch Intern Med 1999; eTG complete):

First-line: doxycycline 100 mg twice daily PLUS hydroxychloroquine 200 mg three times daily for a minimum of 18 months (endocarditis: typically 24–36 months)
Hydroxychloroquine alkalinises the phagolysosome, restoring doxycycline’s intracellular activity against the acidophilic Coxiella
PBS: doxycycline PBS general; hydroxychloroquine PBS Authority Required for this indication (chronic Q fever endocarditis)
Monitoring: Phase I IgG titres every three to six months; treatment continues until Phase I IgG falls below 1:200 (usually 18–36 months); ophthalmology review every twelve months for hydroxychloroquine retinopathy
Infectious diseases physician oversight is mandatory for chronic Q fever — do not manage as a GP alone
Cardiac surgery input if valve function deteriorating despite medical therapy

Serology follow-up after acute Q fever: retest at three and six months to detect early-phase elevation of Phase I IgG titres suggesting progression to chronic infection. This is particularly important in patients with valvular heart disease, vascular grafts, or immunosuppression.

Prevention and Q-VAX vaccination

Q-VAX (CSL Behring, Australia) is the only commercially available Q fever vaccine in the world and is an Australian development. It consists of whole-killed Phase I Coxiella burnetii and provides durable protection (estimated 5–10 years or longer based on cohort data) against clinical Q fever in previously seronegative individuals.

Critical prerequisite — pre-vaccination screening (Australian Immunisation Handbook):

Before administering Q-VAX, two tests must be completed and interpreted:

Skin test (intradermal injection of diluted Q fever antigen; read at 48 hours): a positive reaction (induration ≥5 mm) indicates prior sensitisation — vaccination is contraindicated
Blood serology (Phase I and Phase II IgG by IFA): any positive titre contraindicates vaccination

If either test is positive, Q-VAX is absolutely contraindicated. Administering Q-VAX to a previously immune person causes a severe delayed hypersensitivity reaction — a painful, indurated granuloma at the injection site, sometimes accompanied by fever and systemic symptoms, lasting weeks.

Never administer Q-VAX without documented negative pre-vaccination skin test and serology results, regardless of the clinical circumstances or the patient’s insistence that they have not had Q fever. A history-negative prior infection is common.

Who should be vaccinated (Australian Immunisation Handbook):

Abattoir and meatworks workers
Livestock farmers, shearers, and livestock contractors
Veterinarians, veterinary nurses, and veterinary students
Laboratory workers handling Q fever specimens or potentially infected animal material
Workers at rendering plants, tanneries, and hide-processing facilities

The Q Fever Management Program (qfever.org) provides the national framework for occupational Q fever vaccination, tracks pre-vaccination test results, and coordinates with employers under Work Health and Safety legislation. The vaccine is funded under the National Immunisation Program for eligible workers subject to state arrangements.

B. Evidence appraisal

The case for doxycycline in acute Q fever is supported by multiple clinical cohorts and is the international consensus recommendation. The combination doxycycline-plus-hydroxychloroquine regimen for chronic Q fever endocarditis was established by Raoult et al (Arch Intern Med 1999) and remains the standard of care. No RCT has compared regimens (the rarity of chronic Q fever precludes RCT design), but observational data from the Marseille series and subsequent cohorts consistently demonstrate superiority of the combination over doxycycline alone for long-term Phase I IgG titre reduction and relapse prevention.

Q-VAX efficacy is supported by the original Marmion cohorts (Queensland) and subsequent occupational cohort data, demonstrating greater than 83 per cent protection against clinical Q fever in vaccinated seronegative workers. The pre-vaccination testing requirement is not merely procedural — the granulomatous reaction in pre-immune individuals is reproducible, predictable, and has caused significant morbidity in cases where the protocol was not followed.

Post-Q fever fatigue syndrome remains incompletely understood. Randomised trials of doxycycline, cognitive behavioural therapy, and graded exercise therapy have shown modest benefit for some patients; current treatments do not reliably resolve the syndrome. The mechanism is likely post-infectious immune dysregulation rather than active ongoing infection.

C. Australian operations — MBS, notification, and the Q Fever Management Program

Notification: all probable and confirmed Q fever cases must be notified to the relevant state or territory health department under the National Notifiable Diseases Surveillance System. Most states require notification within five working days of a positive serological result; check your state’s requirements.

MBS items (MBS Online):

Consultations: standard item 23/36/44; long consultation appropriate for initial occupational health assessment or vaccination pre-screening
Q fever serology — immunofluorescence assay (IFA) for Phase I and Phase II IgG and IgM: item 69308 (preferred); complement fixation testing item 69303
LFT and transaminases: item 71365 range
Pre-vaccination skin test administration: GP procedural item under item 10990 range or equivalent
ATSI annual health check item 715 for occupational health screening in rural and remote communities

PBS medications (PBS Online):

Doxycycline 100 mg — PBS general listing; dispensed as capsules or dispersible tablets; course: 28 capsules for a 14-day acute treatment course
Hydroxychloroquine — PBS Authority Required for chronic Q fever endocarditis (blood test confirming seropositivity required for Authority); ongoing supply requires six-monthly review

The Q Fever Management Program (qfever.org): GPs who offer occupational Q fever vaccination should register as providers. The program tracks pre-vaccination test results in a national database to prevent inadvertent vaccination of seropositive workers. Consent forms, testing records, and vaccination records are maintained through the program. Employers have a Work Health and Safety obligation to offer vaccination to eligible workers and must retain records.

Workers’ compensation: Q fever acquired in the workplace is a compensable injury under state-based workers’ compensation legislation. Document the occupational exposure history clearly, notify the relevant authority, and advise the worker to notify their employer.

D. Other important Australian zoonoses

Leptospirosis (Leptospira interrogans): Australia’s second most important zoonosis, transmitted by contact with water, soil, or mud contaminated with urine from infected animals — mainly cattle, pigs, rats, and dogs. Tropical northern Queensland accounts for the highest Australian incidence.

Classic presentation: flu-like illness with intense myalgia (muscle tenderness, particularly calf muscles), severe headache, conjunctival suffusion (bilateral red eyes without discharge — a distinctive sign that differentiates leptospirosis from most viral illnesses), and fever. Weil’s disease (severe leptospirosis): jaundice, oliguric renal failure, pulmonary haemorrhage, and aseptic meningitis; mortality approximately five to ten per cent.

Diagnosis: leptospiral serology (microscopic agglutination test, MAT) and PCR of blood or urine in the first week.

Treatment (eTG complete; AMH): mild to moderate — doxycycline 100 mg orally twice daily × 7 days; severe — IV penicillin or IV ceftriaxone. Notify state health department.

Hendra virus: Hendra virus is a paramyxovirus of the Henipavirus genus maintained in Australian flying foxes (fruit bats) and transmitted to horses by direct contact or aerosol from flying fox secretions. Humans acquire infection from close contact with infected horses — particularly during respiratory procedures, handling secretions, or performing necropsies on sick or dead horses.

Human Hendra disease: incubation two to sixteen days; presents with influenza-like illness followed by encephalitis in most cases; case fatality rate approximately 50 per cent in the small number of confirmed human cases to date. No licensed human treatment or vaccine exists; ribavirin and m102.4 antibody have been used experimentally.

Clinical action: any person with febrile illness who has had close contact with a horse in eastern Australia — particularly if the horse was ill or died — should be assessed as a possible Hendra case. Contact the relevant state public health unit immediately; isolation, PPE, and specialist infectious diseases review are required.

A registered equine Hendra vaccine (Equivac HeV) is available for horses in Australia. GP awareness of its existence and encouraging vaccination of horses in high-risk areas (eastern Australian flying fox habitat) is an important community-level prevention message for rural patients who work with horses.

Brucellosis (Brucella spp.): rare in Australia since eradication from cattle in the 1990s, but still occurs in feral pig hunters (B. suis). Presents with undulant fever, night sweats, and myalgia. Diagnosis by culture and serology. Treatment: doxycycline plus rifampicin. Notifiable.

Psittacosis (Chlamydophila psittaci): transmitted from parrots, cockatiels, and other birds; presents as atypical pneumonia with splenomegaly. Diagnosis by serology. Treatment: doxycycline.

E. Special populations

Occupational at-risk workers: the entire Q fever risk-management pathway — pre-vaccination screening, vaccination, post-exposure monitoring — is primarily an occupational health process. GPs practising in rural Queensland, New South Wales, and Victoria with livestock farming communities should be comfortable administering the pre-vaccination skin test and interpreting paired serology. Familiarity with the Q Fever Management Program is essential.

Pregnant women: acute Q fever in pregnancy is associated with adverse outcomes including miscarriage, foetal growth restriction, and premature birth. Doxycycline is contraindicated in pregnancy; co-trimoxazole is the first alternative in conjunction with infectious diseases oversight. Pregnant women in high-risk occupations should be excluded from the highest-risk exposure points (lambing, calving, kidding) until they have either been vaccinated prior to pregnancy or can be confirmed seronegative and managed with enhanced infection control.

Immunocompromised patients: the risk of chronic Q fever is substantially elevated in organ transplant recipients, HIV patients, and those receiving long-term immunosuppression. Extended serological surveillance (Phase I IgG every three to six months for at least two years) following any acute Q fever in these patients is recommended, with a low threshold for infectious diseases referral.

Aboriginal and Torres Strait Islander people in rural and remote settings: occupational exposure through mustering, shearing, and abattoir work is common. Vaccine access through ACCHS is a priority equity issue. Closing the Gap health targets include reducing the infectious disease burden in remote communities.

Children under 8 years: doxycycline is generally avoided in this age group due to dental staining effects; the decision to use doxycycline in severe paediatric Q fever involves an individualised benefit-risk discussion with infectious diseases and the family, given that the risk of dental staining from short-course doxycycline is less than once believed.

When to escalate

Refer to infectious diseases for: confirmed or probable chronic Q fever (endocarditis, vascular graft infection); acute Q fever in immunocompromised patients or pregnant women; any Q fever patient with cardiac valvular disease or prosthetic material (for risk stratification and extended surveillance); post-Q fever fatigue syndrome not resolving with two to three months of standard care.

Notify the state public health unit immediately for: any suspected Hendra virus case; any leptospirosis case requiring hospitalisation; any Q fever outbreak cluster in an occupational setting.

What this article is and is not

This article summarises Australian and international evidence-based guidance on Q fever and other Australian zoonoses to support informed conversations between patients, workers, and clinicians. It is for educational purposes and does not constitute medical advice. Workers in high-risk occupations and their employers should seek advice from their GP, an occupational health physician, or the Q Fever Management Program regarding vaccination and screening. Anyone with suspected Hendra virus exposure should contact the state public health unit before presenting to a clinic, to allow appropriate infection control precautions to be arranged.

Sources cited

Frequently asked questions

What is Q fever and how is it caught?

Q fever is caused by the bacterium Coxiella burnetii, which infects cattle, sheep, goats, kangaroos, and other animals. Humans are infected primarily by inhaling contaminated aerosols — dried birth fluids, placenta, faeces, or wool dust — rather than by direct animal contact. The organism is extraordinarily infectious: a single organism can cause human infection. High-risk occupations include farmers, abattoir workers, shearers, veterinarians, and laboratory workers. Q fever is the most common notifiable zoonosis in Australia, with several hundred to over a thousand cases reported annually, predominantly in Queensland, New South Wales, and Victoria.
Why is the pre-vaccination test for Q-VAX so important?

Q-VAX can cause a severe localised granulomatous reaction — a painful swelling at the injection site lasting weeks — if it is given to someone who is already immune to Q fever, either from a previous infection or a previous vaccination. This reaction can be disabling and is largely preventable with screening. Before any Q-VAX vaccination, two screening tests are mandatory: a skin test (intradermal injection of diluted Q fever antigen, read at 48 hours) and a blood test for Phase I and Phase II Q fever serology. If either test is positive, vaccination is contraindicated. Never administer Q-VAX without performing and interpreting both tests first.
How is acute Q fever treated?

Acute Q fever is treated with doxycycline 100 mg twice daily for fourteen days. Treatment is most effective when started early and significantly shortens the illness duration. Doxycycline is contraindicated in pregnancy and in children under eight years — in these groups, co-trimoxazole or rifampicin are alternatives in consultation with infectious diseases. Most patients with acute Q fever recover fully with treatment. Mandatory notification to the state health department is required for every confirmed case. Serology follow-up at three and six months is recommended to detect progression to chronic Q fever.
What is chronic Q fever and who is at risk?

Chronic Q fever occurs in approximately one to five per cent of people after acute infection, almost always in people with pre-existing conditions that impair local immunity or provide a site for persistent infection. The most common form is endocarditis, affecting people with damaged or prosthetic heart valves — the infection can smoulder silently for months before diagnosis. Other forms include vascular graft infection and chronic hepatitis. Immunocompromised individuals (transplant recipients, HIV, long-term corticosteroids) and pregnant women are also at elevated risk of chronic disease. Treatment requires eighteen months or more of doxycycline combined with hydroxychloroquine, with infectious diseases oversight.
What other Australian zoonoses should GPs know about?

Leptospirosis is the second most important Australian zoonosis, transmitted through contact with water or soil contaminated with urine from infected animals — mainly cattle, pigs, dogs, and rodents. The classic presentation is flu-like with intense myalgia, headache, and conjunctival suffusion (red eyes without discharge), which is a distinctive sign. Severe leptospirosis (Weil's disease) causes jaundice, renal failure, and meningitis. Treatment is doxycycline or penicillin. Hendra virus is a rare but highly lethal paramyxovirus in eastern Australia, transmitted from flying foxes through infected horses to humans — equine handlers who develop febrile illness after contact with a sick or dead horse should be assessed as a Hendra case until proven otherwise.
Who should receive Q-VAX vaccination?

Q-VAX is recommended for people with occupational exposure to Q fever, including abattoir workers, farmers, shearers, livestock handlers, veterinarians, veterinary nurses, and laboratory workers handling Q fever specimens. It is not a routine population vaccination. The Q Fever Management Program (qfever.org) coordinates vaccination nationally. Vaccination is only effective in seronegative, skin-test-negative individuals — screening must come first. The vaccine provides long-lasting protection and is funded under the National Immunisation Program for at-risk workers, subject to state-specific arrangements.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.