Causes of equine abortion, stillbirth, and perinatal mortality in Brazil

ABSTRACT Abortion and complications in reproduction are important causes of economic loss in horse breeding. Studies of its causal agents can help to identify the primary pathogens or other factors involved and define appropriate measures to reduce its occurrence. This research aimed to investigate the primary causes of equine abortion, stillbirth, and perinatal mortality in regions of Brazil. Tissue from aborted fetuses, stillbirths, neonates and foals submitted to the Biological Institute of São Paulo, Brazil, from January 2010 to July 2013 were processed for viral and bacterial isolation, polymerase chain reaction (PCR), histology, and immunohistochemistry. Bacterial infection was the primary detected cause of abortion, found in 16 of the 53 animals submitted for bacterial analysis followed by viruses analysis in 2 of 105 animals, and noninfectious causes (neonatal isoerythrolysis) in 2 of 105 animals. Fungi were found in a single sample of 53 tested. The most frequent bacteria recovered were Escherichia coli, Enterobacter aerogenes, combined E. coli and Streptococcus spp., Staphylococcus spp., and Bacillus spp. The following agents were each observed in a single sample: Arcanobacterium pyogenes, Streptococcus spp., Corynebacterium spp., Actinobacillus spp., and Rhodococcus equi. The predominant identification of fecal and other opportunistic bacteria as opposed to pathogens commonly associated with equine abortion, such as Leptospira spp. and equine herpesvirus type 1 (EHV-1), suggests the need of improving hygiene management of breeding mares to prevent bacterial infection that may cause fetal loss, stillbirth, and perinatal mortality.

摘要：马繁育过程中的流产及繁殖并发症是造成经济损失的重要诱因。对其致病因子开展研究，有助于明确相关主要病原体或其他影响因素，并制定适宜措施以降低此类事件的发生率。本研究旨在探究巴西部分地区马流产、死产以及围产期死亡的主要致病原因。2010年1月至2013年7月期间，送交至巴西圣保罗生物研究所的流产胎儿、死产幼崽、新生马驹及驹体组织样本，被用于病毒与细菌分离、聚合酶链反应（polymerase chain reaction，PCR）、组织学以及免疫组织化学检测。细菌感染是本次检测中发现的主要流产诱因：在53份接受细菌检测的样本中，16份检出细菌感染；105份接受病毒检测的样本中，2份检出病毒感染；另有105份样本中检出2例非感染性病因（新生马同种红细胞溶解症）。53份检测样本中仅1份检出真菌。检出率最高的细菌为大肠埃希菌（Escherichia coli）、产气肠杆菌（Enterobacter aerogenes）、大肠埃希菌与链球菌属（Streptococcus spp.）混合感染、葡萄球菌属（Staphylococcus spp.）以及芽孢杆菌属（Bacillus spp.）。另有以下病原体各在1份样本中检出：化脓隐秘杆菌（Arcanobacterium pyogenes）、链球菌属、棒状杆菌属（Corynebacterium spp.）、放线杆菌属（Actinobacillus spp.）以及马红球菌（Rhodococcus equi）。本次研究中，检出的病原体以粪便来源及其他机会致病菌为主，而非马流产相关的常见病原体（如钩端螺旋体属（Leptospira spp.）及马疱疹病毒1型（equine herpesvirus type 1，EHV-1）），这提示需优化繁育母马的卫生管理措施，以预防可能引发胎儿丢失、死产及围产期死亡的细菌感染。