Abstract. Placentas from aborted, stillborn, and premature foals were examined during the 1988 and 1989 foaling seasons, and 236 of 954 (24.7%) had placentitis. Microorganisms associated with placentitis were isolated or demonstrated from 162 of 236 (68.6%) placentitis cases. Leptospira spp. and a nocardioform actinomycete were 2 important, newly emerging bacteria associated with equine placentitis. Major pathogens identified in decreasing order were Streptococcus zooepidemicus, Leptospira spp., Escherichia coli, a nocardioform actinomycete, fungi, Pseudomonas aeruginosa, Streptococcus equisimilis, Enterobacter agglomerans, Klebsiella pneumoniae, and alpha-hemolytic Streptococcus. Pathogens were not recovered in 64 cases (27.1%) and overgrowth by saprophytic bacteria was recorded in 10 cases (4.2%). Twenty-seven cases (16.6%) had mixed bacterial growth and 93 cases (57.4%) had bacteria cultured from both placenta and fetal organs. The majority of the placentitis cases caused by bacteria, with the exception of Leptospira spp. and the nocardioform actinomycete, occurred in 2 forms. One was acute, focal or diffuse; had an infiltration of neutrophils in the intervillous spaces or necrosis of chorionic villi; was associated with bacteremia; and frequently occurred in the placenta from fetuses expelled before or at midgestation. The other was observed from foals expelled at late gestation, was mostly chronic and focal or focally extensive, and occurred mostly at the cervical star area. Chronic placentitis was characterized by the presence of 1 or a combination of the following lesions: necrosis of chorionic villi, presence of eosinophilic amorphous material on the chorion, and infiltration of mononuclear inflammatory cells in the intervillous spaces, villous stroma, chorionic stroma, vascular layer, and allantois. Chorangiosis, hyperplasia with or without squamous metaplasia of the chorionic epithelim, and adenomatous hyperplasia of the allantoic epithelium were frequently associated with chronic placentitis. Leptospira spp. induced, regardless of gestational age, a diffuse placentitis with the presence of a large number of spirochetes in the stromal tissues. The nocardioform actinomycete, a gram-positive, filamentous, and branching bacillus, induced an unique chronic-active focally extensive placentitis located at the base of the horn or at the junction between the body and horn of the allantochorion. Fungi, with the exception of Histoplasma sp. and Candida sp., induced a chronic focally extensive placentitis at the cervical star area similar to that seen in chronic bacterial placentitis. Histoplasma sp. induced a multifocal granulomatous placentitis, and Candida sp. induced a diffuse necrotizing and proliferative placentitis.Abortion and stillbirth are major causes of equine mortality and cause a severe economic loss to the equine industry. 8,12,16 Causes of abortion and stillbirth are many, but placentitis was considered by some workers as the single most important cause. 17,18 There are few reports on equine place...

Abstract. Pathologic and microbiologic examinations were performed on 1,211 aborted equine fetuses, stillborn foals, and placentas from premature foals in central Kentucky during the 1988 and 1989 foaling seasons to determine the causes of reproductive loss in the mare. Placentitis (19.4%) and dystocia-perinatal asphyxia (19.5%) were the 2 most important causes of equine reproductive loss. The other causes (in decreasing order) were contracted foal syndrome and other congenital anomalies (8.5%), twinning (6.1%), improper separation of placenta (4.7%) torsion of umbilical cord (4.5%), placental edema (4.3%), equine herpesvirus abortion (3.3%), bacteremia (3.2%), fetal diarrhea (2.7%), other placental disorders (total of 6.0%), and miscellaneous causes (1.6%). A definitive diagnosis was not established in 16.9% of the cases submitted. Streptococcus zooepidemicus, Escherichia coli, Leptospira spp., and a nocardioform actinomycete were organisms most frequently associated with bacterial placentitis, and Aspergillus spp. was the fungus most often noted in mycotic placentitis. No viral placentitis was noticed in this series. Dystocia-perinatal asphyxia was mostly associated with large foals, maiden mares, unattended deliveries, and malpresentations. The results of this study indicate that in central Kentucky, the noninfectious causes of equine reproductive loss outnumber the infectious causes by an approximate ratio of 2:1, placental disorders are slightly more prevalent than nonplacental disorders, Leptospira spp. and a nocardioform actinomycete are 2 new important abortifacient bacteria in the mare, the occurrence of contracted foal syndrome is unusually frequent, the incidence of twin abortion has sharply declined, and torsion of the umbilical cord is an important cause of abortion in the mare.Abortion and stillbirth are major causes of equine oughbred, 123 were Standardbred, 40 were American Sadmortality and cause severe economic loss to the equine dlebred, 59 were unspecified, and the remaining included industry. Causes of equine abortion and stillbirth vary Tennessee Walking horse, Arabian, Morgan, Quarter horse, with geographic area and change with time. 1,4,8,13,14,16 Miniature horse, draft horse, and pony. The submissions In early studies, infectious agents were reported as macovered a wide range of gestation ages: 79 were < 180 days, jor causes of equine reproductive loss 4 whereas later 126 were 181-220 days, 135 were 221-260 days, 203 were reports indicated that the loss from noninfectious caus-261-300 days, 538 were over 301 days, and the remaining es, e.g., twinning and stillbirth, surpassed the prevawere of unknown gestation age (Table 1). The submissions were seasonal; the majority of cases were received from Janlence of those caused by infectious agents. 7,8 This report uary to May (Table 2). presents the results from a comprehensive pathologic and microbiologic study on equine abortion and stillBefore gross examination was performed, the foal, allantochorion, and amnion were weighed, and the leng...

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