Abstract
The bacterium Coxiella burnetii has been detected in the fetal membranes, birth fluids and vaginal mucus, as well as in the milk and other excretions of several domestic mammals. The finding of C. burnetii in association with abortion, parturition and in the postpartum period has led to the hypothesis that C. burnetii causes a range of reproductive diseases. This review critically evaluates the scientific basis for this hypothesis in domestic mammals.The review demonstrates a solid evidence for the association between C. burnetii infection and sporadic cases of abortion, premature delivery, stillbirth and weak offspring in cattle, sheep and goats. C. burnetii induced in-herd epidemics of this complete expression of reproductive failure have been reported for sheep and goats, but not for cattle. The single entities occur only as part of the complex and not as single events such as generally increased stillbirth rate. Studies show that C. burnetii initially infects the placenta and that subsequent spread to the fetus may occur either haematogenous or by the amniotic-oral route. The consequences for the equine, porcine, canine and feline conceptus remains to the elucidated but that infection of the conceptus may occur is documented for most species. There is no solid evidence to support a hypothesis of C. burnetii causing disorders such as subfertility, endometritis/metritis, or retained fetal membranes in any kind of domestic animal species.There is a strong need to validate non-pathology based methods such as polymerase chain reaction for their use in diagnostic and research in relation to establishing C. burnetii as the cause of abortion and to adapt an appropriate study design and include adequate control animals when linking epidemiological findings to C. burnetii or when evaluating effects of vaccination in production herds.
Highlights
Coxiella burnetii is a zoonotic obligate intracellular bacterium that has an almost worldwide distribution
In a diagnostic survey based on 211 cases of abortions and stillbirths submitted to diagnostic examination in California, USA, C. burnetii was determined as the cause in 19% and in a diagnostic survey performed in Switzerland, C. burnetii was identified as the cause of abortion in 10% of 144 abortions [83,90]; figures that are far higher than found in cattle and sheep [32,33,39,40,41,82]
A number of studies have focused the prevalence of caprine abortions and other disorders due to C. burnetii using polymerase chain reaction (PCR) or serology [24,27,35,53,79,92,93] with the same limitations as for cattle and sheep as healthy goats may excrete the bacterium in e.g. vaginal mucus [15,26,94,95] and as bacteria may be present in the genital tract of normal does [96]
Summary
Coxiella burnetii is a zoonotic obligate intracellular bacterium that has an almost worldwide distribution. A number of studies have focused the prevalence of caprine abortions and other disorders due to C. burnetii using PCR or serology [24,27,35,53,79,92,93] with the same limitations as for cattle and sheep as healthy goats may excrete the bacterium in e.g. vaginal mucus [15,26,94,95] and as bacteria may be present in the genital tract of normal does [96]. None of the kittens have been examined as the association between the cat’s parturition and outbreak of Q fever was established in retrospective epidemiological investigations and it remains unknown if C. burnetii is associated with the APSW complex in cats
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