Serological evidence of Coxiella burnetii infection in beef cattle in Queensland A Cooper, a * R Hedlefs, b M McGowan, c N Ketheesan a and B Govan a Background Queensland has the highest incidence of Q fever in Australia. The aim of this study was to undertake a cross-sectional seroprevalence survey of Coxiella burnetii, the causative agent of Q fever, in beef cattle in Queensland. Methods Serum samples were tested by ELISA for both phase II and phase I antigens of the organism using an Australian isolate. Blood samples were collected at an abattoir that processes beef cattle originating from northern and north-western Queensland, in addition to blood samples taken from beef cattle across Queen- sland as part of a second survey. Results Seropositivity was 16.8% (95% confidence interval 16.7– 16.8%). Conclusion Evidence of C. burnetii infection in beef cattle has public health implications for occupational exposure of primary producers and veterinarians and for the proximity of beef cattle properties to residential areas in regional Queensland. This study is the first known investigation of C. burnetii seroprevalence in beef cattle in Queensland and the first known use of an Australian C. burnetii isolate for screening using both phase II and phase I antigens. Keywords Australia; beef cattle; Coxiella burnetii; Q fever; Queen- sland; serology Abbreviations CI, confidence interval; ddH2O, double-distilled water; ELISA, enzyme-linked immunosorbent assay; Ig, immunoglo- bulin; LPS, lipopolysaccharide; OD, optical density; PBS, phosphate- buffered saline Aust Vet J 2011;89:260–264 doi: 10.1111/j.1751-0813.2011.00794.x Q fever is a worldwide zoonosis caused by Coxiella burnetii, an obligate intracellular bacterium. 1 In animals the infection is referred to as coxiellosis. The organism is ubiquitous, with a geographical spread extending worldwide, with the exception of New Zealand. 2 Coxiella burnetii exists in two antigenically different phases, which are characterised by transition of lipopolysaccharide (LPS) from a smooth form with full-length O-side chains in phase I to a rough form with truncated O-side chains in phase II. In humans, differences in the titres of immunoglobulin (Ig) subsets to phase I or II antigens form the basis for diagnosis of acute (antibodies to phase II antigens) or chronic (antibodies to phase I antigens) Q fever. 1 It has been demonstrated that animals infected with C. burnetii produce antibodies to both phase I and phase II antigens. 3 Most commercial animal Q fever enzyme-linked immunosorbent assays (ELISAs) consist of a mixture of phase I and phase II antigens. The domestic reservoir, consisting of cattle, sheep and goats, is con- sidered the major source of transmission of C. burnetii infection to humans in Australia. Coxiella burnetii is thought to be initially trans- mitted to livestock via ticks, which form part of the natural transmis- sion cycle of the organism in wildlife. Kangaroos 4,5 and bandicoots 6 have been identified as potential reservoirs of Q fever in Australia. Human infection is usually acquired by inhalation of contaminated material from infected animals. Less commonly, infection may result from consumption of infected animal products, such as unpasteurised milk.Very rarely, it may result via sexual transmission following expo- sure to infected body fluids. 7 Those most at risk of Q fever infection include individuals with occupational contact with reservoir animals, particularly those in the meat and livestock industries, veterinarians and laboratory workers. 1 The organism is capable of long-term envi- ronmental persistence, it being suggested but not conclusively shown that this persistence may be in a spore-like form. 1 As a result of environmental contamination, a number of outbreaks of Q fever are reported to have occurred following strong winds blowing through areas where livestock are bred, held or transported. 8,9 Since 1934, when sporadic cases of fever with a typhoid-like presen- tation became apparent to medical practitioners in Brisbane, out- breaks of Q fever in Australia have been predominantly associated with abattoirs. 10 In a recent series of cases over a 20-year period in southern Australia, 92% of the 111 cases of Q fever were among abattoir workers. 11 In North Queensland, a study of Q fever cases during 1994–2006, found that 22% of acute and 33% of chronic Q fever patients reported exposure to cattle. 12 This trend extends internationally, where an occupation in the meat-processing indus- tries has been associated with increased risk of Q fever infection. 1 Infections in animals are usually subclinical, although infection can be associated with abortions and reproductive disorders. 13–15 Seropositiv- ity is believed to be seasonal in livestock, particularly sheep, as sero- logical studies indicate the presence of recurring annual cycles of antibody prevalence in response to C. burnetii exposure during lamb- ing. 16 More recent studies in dairy cattle indicate that seropositivity is related to changes in endocrine patterns during gestation. 17 However, these studies were performed overseas and no comparable data are available for Australia. In epidemiological studies during the past 6 years, the seroprevalence of C. burnetii in cattle populations has varied according to geographical location: 6.2% in Northern Ireland, 18 87.9% in Albania, 19 10.75% in Iran, 20 14.3% in the Central African Republic, 21 24% in Newfoundland 22 and Cyprus 23 and 25.6% in Korea. 24 Previous serological investigations of the prevalence of C. burnetii infection in Australian cattle *Corresponding author. a School of Veterinary & Biomedical Sciences, James Cook University, Townsville, Queensland, Australia; Alanna.Cooper@jcu.edu.au b Department of Employment, Economic Development & Innovation, Townsville, QLD, Australia c School of Veterinary Science, University of Queensland, Gatton Campus, QLD, Australia PRODUCTION ANIMALS PRODUCTION ANIMALS © 2011 James Cook University Australian Veterinary Journal © 2011 Australian Veterinary Association Australian Veterinary Journal Volume 89, No 7, July 2011 260