A racing start in life? The hurdles of equine feto‐placental pathology

Abstract

SummarySignificant progress has been made in understanding and monitoring the causes of equine abortion over past decades. However, not all in utero pathology results in abortion. It has long been recognised that some in utero pathology, such as twinning or chronic placentitis, can result in the birth of live but growth-retarded foals and there is historical evidence that birth weight may influence future athletic performance. Clinical experience (e.g. from twins) and experimental studies (pony-Thoroughbred embryo transfer) have highlighted the importance of reduced functional placental area in limiting growth in utero in horses. Many other nonfatal in utero pathologies (e.g. umbilical cord-related circulatory compromise) can potentially affect either placental function or other organ systems. Their influence on the short-and long-term health of the foal and its future athletic performance is in many cases poorly documented or understood. This review summarises the main causes of in utero pathology and reflects on how these may potentially affect the foal if born alive, highlighting the need for long-term studies on this important subject.

Pathology of equine amnionitis and foetal lLoss: clinical and experimental studies

“…Equine abortion investigations require the necropsy of the foetus and foetal membranes with collection of tissues and fluids for bacterial culture, virological testing, and histopathology (Foote et al, 2012). The gross lesions visualized during the necropsy can be as important as the testing in determining the ultimate cause of the abortion (Morresey, 2005).…”

“…Histopathology specimens encompass the cervical pole and umbilical insertion areas of the placenta, section of the umbilical cord between the amnion and placenta, amnion, and internal organs (Whitwell, 2011). By taking this minimum number of specimens, it is generally possible to diagnose most of the known causes of abortion (Morresey, 2005;Whitwell, 2011;Foote et al, 2012). Equally important, the set protocol of examination and specimen collection provides a solid base for investigating any "unknown" or new causes of abortion as will be described in both the clinical and experimental chapters of this thesis.…”

“…Thrombosis and hypoxia are likely underlying causes of ischaemic necrosis of the cervical pole of the allantochorion in horses possibly due to long cord length (Foote et al, 2012).…”

“…This usually results in a freshly aborted foetus, which may be growth retarded (placental lesions are very extensive), and with lesions consistent with acute hypoxia due to abrupt placental separation (Foote et al, 2012). Secondary ascending bacterial placentitis may also be present (Smith et al, 2003).…”

“…In one case study the principle change histologically was calcified material in the vasculature of the allantochorion (Williams, 2002). Body pregnancy Body pregnancy is uncommon but occurs when the foetus and foetal fluids do not extend into the uterine horns despite normal implantation (Foote et al, 2012).…”