Etiology and pathology of equine placentitis.

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.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1993-01-01 PubMed ID: 8466982DOI: 10.1177/104063879300500113Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't


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The research article is about a study conducted during 1988 and 1989, examining the origins and disease progression of placentitis in horses, including the key pathogens identified, common characteristics and findings, and differences based upon gestational stage.

Objective of the Research

  • The main goal of this study was to investigate the causes and nature of placentitis in aborted, stillborn, and premature foals during the 1988 and 1989 breeding seasons. This involved understanding the microorganisms linked to placentitis and outlining the primary diseases present, as well as tracking the differing appearances and effects of the condition based on the gestational period.

Key Findings

  • The researchers discovered that placentitis occurred in 24.7 percent of the cases (236 out of 954). They further identified microorganisms linked to placentitis in 68.6 percent of the placentitis instances (162 out of 236).
  • Two new bacteria associated with equine placentitis, namely Leptospira spp. and a nocardioform actinomycete, were discovered during this study.
  • The major pathogens found include Streptococcus zooepidemicus, Leptospira spp., Escherichia coli, a nocardioform actinomycete, Pseudomonas aeruginosa, fungi, and others. However, in 27.1 percent of the cases, pathogens were not found.

Diversity in Appearance and Conditions

  • The research highlights two types of appearance for placentitis cases arising from bacteria (with the exception of Leptospira spp. and the nocardioform actinomycete).
  • One type is acute and associated with bacteremia, found either in localized or widespread form, often observed in fetuses expelled before or at mid-gestation.
  • The other type, typically noted in foals expelled later in gestation, is chronic and often located at the cervical star area. It is characterized by necrosis of chorionic villi, presence of eosinophilic amorphous material on the chorion, and infiltration of various inflammatory cells.

Cite This Article

Hong CB, Donahue JM, Giles RC, Petrites-Murphy MB, Poonacha KB, Roberts AW, Smith BJ, Tramontin RR, Tuttle PA, Swerczek TW. (1993). Etiology and pathology of equine placentitis. J Vet Diagn Invest, 5(1), 56-63.


ISSN: 1040-6387
NlmUniqueID: 9011490
Country: United States
Language: English
Volume: 5
Issue: 1
Pages: 56-63

Researcher Affiliations

Hong, C B
  • Livestock Disease Diagnostic Center, University of Kentucky, Lexington 40511.
Donahue, J M
    Giles, R C
      Petrites-Murphy, M B
        Poonacha, K B
          Roberts, A W
            Smith, B J
              Tramontin, R R
                Tuttle, P A
                  Swerczek, T W

                    MeSH Terms

                    • Abortion, Veterinary
                    • Allantois / microbiology
                    • Allantois / pathology
                    • Animals
                    • Bacteria / isolation & purification
                    • Bacterial Infections / pathology
                    • Bacterial Infections / veterinary
                    • Chorion / microbiology
                    • Chorion / pathology
                    • Female
                    • Fetal Death / veterinary
                    • Horse Diseases / etiology
                    • Horse Diseases / pathology
                    • Horses
                    • Inflammation
                    • Placenta / microbiology
                    • Placenta / pathology
                    • Placenta Diseases / etiology
                    • Placenta Diseases / pathology
                    • Placenta Diseases / veterinary
                    • Pregnancy


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