Investigation of bovine abortion and stillbirth/perinatal mortality - similar diagnostic challenges, different approaches.

Abstract

This pracademic paper reviews current bovine foetopathy (abortion and stillbirth) case definitions, reporting and triage, and causes and time-of-death and proposes veterinary practitioner-focused investigative standard operating procedures (SOPs). Issues of under- and over-triage and intra-institutional SOP harmonisation are also discussed. It is proposed that an 'observable abortion' (120-260 days of gestation) is a more practitioner-friendly definition of abortion for reporting and benchmarking purposes and that the term 'peristillbirth' can replace stillbirth and perinatal mortality. Diagnosis of bovine foetopathy involves an investigative triad of the farmer, veterinary practitioner and the veterinary diagnostic laboratory. However, the poor sensitivity of abortion reporting undermines the value of currently adopted scanning/passive surveillance; parallel active surveillance/sentinel herd models should also be employed. The approach to abortion investigation differs from that of peristillbirth. The former should include collecting a herd and case history, examination and sampling of dam and cohorts and sampling of the foetus and placenta. A sample selection decision tree is provided to assist test selection. In peristillbirths, non-infectious and periparturient causes-of-death are more important hence the anamnesis must focus on peristillbirth risk factors and calving management. The foetopsy, while including the sampling menu appropriate to aborted foetuses, must also include a detailed internal and external examination of the carcass for lesions indicative of periparturient causes-of-death. In addition, for aborted foetuses the time-of-death is not important as the foetus is generally not viable; however, for the peristillbirth the time-of-death is critical as it provides useful information for the farmer to address modifiable risk factors and to alter their perinatal management. Reporting of the ultimate cause-of-death is more useful to prevent future abortions and peristillbirths though the proximate cause-of-death is often reported in the absence of a complete clinical anamnesis. Finally, the common reasons for diagnosis not reached (DNR) and the limitations of current investigative approaches are discussed.