Abstract
Uterine diseases in cattle occur at all stages of the reproduction cycle but the majority of cases is found in the postpartum period. The inflammation of the uterus is generally defined as metritis or endometritis, with several graduations, e.g. puerperal metritis, clinical metritis, clinical or subclinical endometritis. Whether uterine diseases have a negligible, moderate or detrimental effect on fertility is still under discussion and depends on definitions and classification. In the past, it was assumed that the pregnant uterus is free of pathogens, but recent studies found several species including pathogens in the uterus and endometrium of pregnant cows. After parturition, a broad diversity of bacteria with >200 different species has been found in the early postpartum period. Not all of these bacteria, however, are considered as pathogens. Furthermore, bacteriological findings provide only evidence for infection but not for inflammation. For some bacteria, particularly Escherichia coli and Trueperella pyogenes pathogenic mechanism resulting in metritis and endometritis have been elucidated in detail. The role of bacteria that can be regarded as opportunistic or potential pathogens, e.g. Bacillus pumilus, is still under investigation. The understanding of the uterine microbiota and its interactions is increasing with the use of modern high-resolution techniques such as Fourier- transform infrared spectroscopy. Endometrial cytology provides additional information about alterations in the endometrium. Knowledge of innate uterine defense mechanism in cattle has increased a lot in the recent past. It can be speculated that improving or modulating uterine defense mechanism will be part of future prevention and treatment approaches beyond the use of antimicrobials. In this context, cellular and molecular defense mechanisms have been in the focus of interest, e.g. the role of interleukins or mucins. This review gives a short overview on some aspects of recent research on uterine diseases in cattle.
Highlights
Reproductive performance of cows and heifers is one of the key parameters reflecting the economic success of dairy farming
Recent studies indicate that S. uberis and B. pumilus (Wagener et al, 2014b, 2015) might represent such bacterial candidates with a hitherto unknown role in uterine pathology
Hailemariam et al (2014) found miRNAs that were differentially expressed in cows with subclinical endometritis, and that are involved in inflammatory responses, cellular proliferation, cell movement, the cell cycle and apoptosis
Summary
Reproductive performance of cows and heifers is one of the key parameters reflecting the economic success of dairy farming. Recent studies indicate that S. uberis and B. pumilus (Wagener et al, 2014b, 2015) might represent such bacterial candidates with a hitherto unknown role in uterine pathology Both bacteria are prevalent in postpartum dairy cows. As shown in some of the above mentioned studies (Santos et al, 2011; Santos and Bicalho, 2012; Wagener et al, 2015), it has to be underlined that in several cows with clinical signs of metritis and endometritis, neither E.coli nor T. pyogenes can be detected In this context, the role of anaerobic bacteria, e.g. Porphorymonas spp., as a causing factor as well as a factor for cure rates after antibiotic treatment of metritis needs to be elucidated more in detail (Jeon et al, 2017, 2018). Further research is required to understand the association between uterine diseases and hitherto unknown species (Santos et al, 2011; Wagener et al, 2014a)
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