Coxiella in ruminants

Query fever (Q fever) is a zoonosis caused by gram-negative bacteria of the genus Coxiella. Coxiella burnetii, which is the only Coxiella species, generally causes an asymptomatic infection in domesticated animals such as cattle, sheep and goats. It is also found in various tick species. The organism is highly resilient and survives for a long time in faeces, urine, milk and tissue. Therefore, it quickly leads to infectious dust or aerosols. Infections in humans occur frequently in persons working closely with animals or animal products, i.e. in occupational groups such as farmers, veterinarians, shepherds and slaughterhouse staff. The pathogen is generally transmitted through the inhalation of infectious aerosols or dust or by consumption of raw milk contaminated with the bacteria. C. burnetii is highly infectious and classified as risk group III by the WHO.

In case of coxiellosis, non-pregnant ruminants such as cattle, sheep and goats often show an asymptomatic disease course. However, infected animals secrete the pathogen via body fluids and faeces. The concentrations of bacteria are especially high in the amniotic fluid and placenta. Pregnant animals often have premature births or abortions. Since large amounts of Coxiella enter the environment during the birthing process, the risk of zoonosis is very high.

The diagnosis of C. burnetii infection is based on pathogen detection and serology. The PCR test is generally used to determine the pathogen: Milk samples from collection tanks are analysed to determine the Coxiella status of a herd. Individual animals can only be designated as Coxiella-free if the herd is pathogen-free and no serological and clinical evidence of Q fever can be detected. In the case of abortions or stillbirths, samples of the aborted foetus, placenta or vaginal swabs are examined for C. burnetii using a PCR test. Serological tests are also suitable for herd diagnostics. Anti-C. burnetii antibodies are present in acute and past infections: In acute Q fever, the IgG titer against phase 2 antigens is elevated; in the chronic form, high IgG levels are found against phase 1 and 2 antigens of the bacteria. Recent studies show that phase-specific ELISAs achieve a higher sensitivity in the detection of antibodies against C. burnetii in sheep than those using a mix of phase 1 and phase 2 antigens. Phase-specific serology also provided more accurate information on the immune response in sheep after vaccination against the pathogen.

• Anti-Coxiella burnetii Phase 1 ELISA Ruminant (IgG)
• Anti-Coxiella burnetii Phase 2 ELISA Ruminant (IgG)

The diagnosis of acute or chonic Q fever is made by comparing the titers of IgG antibodies against phase 1 and phase 2 antigens. The test results should not be evaluated individually. Furthermore, information on the age and the vaccination status of the animals is helpful for result interpretation.