Q fever – cut the bull!
Stephanie Hendry B Biomed Sci* |

*Graduate Entry Medical Program III, Flinders University

Abstract

Q fever is a zoonotic infectious disease with a large occupational association, predominately with meat workers and the agriculture industry. Although often asymptomatic, it can have various short term and long term sequelae, including infective endocarditis. An effective vaccine was developed in 1989 but was of limited use until 2001 when the Australian Government established the National Q Fever Management Program (NQFMP) for high risk occupations. This program was associated with a halving of the reported Q fever cases. The program ceased after three years as funding was spent, and has not been followed by any similar initiatives. The meat industry continues to have a strong vaccination culture despite a lack of funding. However this movement was not seen in the more independent agriculture industry. Further monitoring is required to determine the success and cost-effectiveness of the NQFMP. Once this occurs, a re-establishment of the NQFMP may be indicated.

Introduction

In Australia, Q fever is largely an occupation-associated infectious disease.  It can result in significant morbidity and time off work.  A relatively effective vaccine has been available since 1989, but there are still 300 cases reported annually.  After introduction of the National Q Fever Management Program (NQFMP) there was a halving of reported cases, but with cessation of the vaccination program in 2006, a further drastic reduction cannot be expected.  The aim of this article is to explore the impact of the NQFMP and review the available trends since its cessation. This helps to identify current gaps in the data on vaccination and Q fever, and therefore suggests further areas of research.

The Organism
Q fever is an infectious disease caused by the obligate intracellular bacteria Coxiella burnetii.  The disease was first recognised in the mid-1930s amongst a group of abattoir workers and farmers in Brisbane.  Edward Derrick documented the disease and isolated an unknown organism responsible for causing fevers in this group of workers.  Hesitant to name it, he called it “Query Fever” which was shortened to Q fever.  Derrick sent infected tissue to Macfarlane Burnet in Melbourne, who identified the organism to be Rickettsiae-like.  Herrald Cox in Montana, USA subsequently identified and classified it as a new genus, Coxiella burnetii, in recognition of his and Burnet’s work (1).

Q fever is a zoonotic disease acquired from wild and domestic animals.  In Australia it is most commonly acquired from cattle, sheep and goats however other animal reservoirs exist including kangaroos, bandicoots, camels and rabbits (1-4).  The bacteria are present within urine, faeces, milk products, or animal birth products.  Humans are inoculated directly via aerosol inhalation of these products or indirectly through inhalation of contaminated products such as dust (1). The spore-like properties of Coxiella burnetii explain the high level of physical resistance it displays.  It is thought to survive in the environment for months to years (5).

Clinical Manifestations
The effects of Q fever vary from country to country and host to host.  It is estimated that 60% of cases are asymptomatic (2,6,7). Acute Q fever has a variable incubation period of approximately three weeks (1,8) and symptoms last for one to three weeks without treatment (8).  In Australia the common clinical manifestation is of a non-specific, flu-like presentation which can lead to misdiagnosis and underestimation of disease rates (1,9). Complications can occur with acute Q fever and include hepatitis, pneumonia, headaches and, in rare cases, meningitis and encephalitis (2,10).  In Switzerland and Spain, pneumonia is the most common presentation, whereas in France and Ontario, Canada, hepatitis predominates.  Q fever occurs worldwide with the exception of New Zealand (10). 

After acquiring acute Q fever some individuals may progress to chronic Q fever.  Those that progress often have pre-existing valvular disease, immunosuppression and other co-morbidities (11).  The most common forms of chronic Q fever are infective endocarditis (60-70%) and post-Q fever fatigue syndrome (10-20%) (6). Both forms are very difficult to treat, carry significant morbidity, and have a mortality rate of less than 5% (2,12,13). 

Diagnosis and Management
Diagnosis of Q fever is usually made by serological detection of IgM and IgG levels to phase II (acute) and phase I (chronic) antigens (2). Acute Q fever can also be detected by Polymerase Chain Reaction in the first eight to ten days after exposure (1). Treatment for acute Q fever involves two weeks of antibiotics, commonly doxycycline (14). Infective endocarditis management requires a minimum of 18 months of antibiotics (doxycycline and hydroxychloroquine), five years monitoring and in selected cases cardiac surgery (11).

Occupational Exposure
The highest reported occupational occurrence is seen in the meat industry (60%), followed by the agricultural industry (30%) (13). Any occupation where employees are exposed to cattle, sheep, goats, camels and kangaroos, or their biological fluids, are at high risk (8).  This includes sheep shearers, stockyard workers, animal transporters, veterinarians, agricultural staff and laboratory personnel (8).  The occupational data recorded reflects these associations, as does the typical patient demographics (1,4).

Costs to Industry
There is a significant financial cost associated with Q fever.  Occupation-acquired, laboratory-proven Q fever is largely compensable (15).  Work Cover compensation claims are estimated to cost $1.3 million per year (13).   Legal payouts can be substantial with a $1.1 million payout from an isolated case of occupation-acquired chronic Q fever recorded (13). Other costs include medical expenses and replaced labour, estimating 1700 weeks of work are lost annually from the disease (1).  

Vaccine Efficacy
Since 1989 a whole-cell, formalin-inactivated vaccine has been available for use.  The Q-VAX® vaccine can have serious adverse reactions if given to a previously exposed or vaccinated individual (1,8).  Therefore, a thorough history of previous infection or vaccination, skin testing and antibody titres are required before vaccination can occur (7).  A literature review by Chiu and Durrheim analysed seven studies to determine the efficacy of the vaccine in Australia.  Although the vaccine efficacy ranged between 83-100% and none of the studies were conducted under ideal conditions (3), the general consensus was that the vaccine is highly protective (>95%) for individuals with high exposure risk, as long as it is given fifteen days prior to exposure (15).

The National Q Fever Management Program
In the early 1980s, before the release of the Q-VAX® vaccine, between 600 and 800 new cases were being reported each year (16). 

Stroke death rates by sex, 1987-2007. Sourced from AIHW (6, p. 81.)
Figure 1. Q fever notification annual rates from 1991-2010 (Data from the National Notifiable Diseases Surveillance System)

Figure 1 shows the disease trend since 1991.  Although the vaccine was available from 1989 there was limited uptake until 1994.  This was when the vaccine manufacturer, CSL Limited, ran a national campaign to inform and help establish vaccine programs in large abattoirs (12,16).  This vaccination uptake was not followed elsewhere and the reported rates reflected this (7,12). During 2001-2002 the Australian Government established the NQFMP which ran in two phases to provide free vaccination to some high risk occupations.  Phase I included abattoir workers, contractors and sheep shearers.  Phase II included sheep, dairy and beef cattle farmers, employees and unpaid family members working on farms (4,7).  Funding was only supplied for three years, and so the program ceased during 2004-2006.  Although the full success of the program is hard to estimate, the greater than 50% reduction in notification rates seen from 2002-2010 has been largely attributed to it (7,17). In 2003 an economical analysis was performed to determine the potential cost effectiveness of the NQFMP.  This assumed 100% vaccination uptake among meat workers and 20% among agricultural workers, and showed this to be very cost effective (13).

The response to the NQFMP
The response to the NQFMP varied between states and occupations.  The overall uptake of the vaccine was estimated at 50-54% nationally (7), with a higher uptake in Phase I than Phase II. A Southern Queensland study by Palmer et al. (2007) demonstrated the consequences of a low vaccine uptake during 2000-2006.  At least 71% of occupation-acquired Q fever cases were unvaccinated despite the majority (92%) being eligible under the NQFMP (12).  Massey et al. (2009) displayed similar results in a New South Wales (NSW) study from 1993-2007, with all 38 cases unvaccinated despite the majority being aware of the vaccine.  Being naive to risk and access problems were the most common reasons for not being vaccinated (18).

Change in Occupational Incidence
The meat industry appears engaged in Q fever prevention with 95% maintenance of vaccination programs after cessation of the NQFMP (4,13) and continuous employee registration of vaccination status via the National Q Fever Register.  This is in significant contrast to the agriculture industry.  Monitoring in NSW showed a possible change in the leading occupation from meat workers to agricultural workers during 1993-2007 (18).  However, monitoring of occupational trends was difficult as occupation was reported in less than 50% of cases and the difference was not statistically significant. 

Trends since NQFMP cessation
Previous data shows low vaccination rates occur without a vaccination program.  Now that the NQFMP has been established and subsequently ceased, the onus is on the employers to provide staff vaccination.  Fear of litigation is a strong incentive for employers to provide vaccination but vaccination is not mandatory (19).  In the 2007-2008 the national health budget of $16.6 million was committed to the “National Immunisation Program – Q Fever Vaccine” which solely assists CSL Limited to continue to produce and supply the vaccine until 2016 (20).  No other funded vaccination programs exist.

Conclusion
Following termination of the NQFMP the future epidemiology of Q fever remains unclear.  Nearly five years after complete NQFMP cessation there are still 300 cases of Q fever reported annually.  The meat industry has shown significant declines in Q fever notification rates and continues to provide vaccination programs for the majority of workers.  However, the agriculture industry is behind.  Further surveillance is needed to determine the effectiveness of the NQFMP and the association with the agriculture industry.  A cost-effective analysis determining the value in a vaccination program among agriculture workers is needed.  This could determine if re-introduction of a government-funded or subsided vaccination program is warranted. 

Acknowledgements

None declared

Conflicts of Interest
None declared

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