Equis ISSN 2398-2977

Abortion: overview

Contributor(s): Annalisa Barrelet, Terry Blanchard, Graham Munroe, Madeleine L H Campbell

Abortion

Print off the Owner factsheets on Abortion and The pregnant mare - health and well-being to give to your clients.

Definition

  • Expulsion of non-viable fetus before day 300 of gestation   Fetus: abortion 03 - pathology  .
  • If after 40 days may be classified as early fetal death (EFD) Abortion: early embryonic / fetal death.
  • If after the first pregnancy diagnosis and before 40 days, it is classified as early embryonic death (EED) - the distinction between an embryo and a fetus being made at 40 days, when organogenesis is complete in the mare.

Incidence

  • Vary according to different studies 2-14%.
  • Usually sporadic, with the exception of EHV-1 Abortion: EHV-1 which may cause groups of abortions, or abortion 'storms'.
  • Unusual for a mare to abort in consecutive years, except in individuals that repeatedly conceive twins Twinning which are not diagnosed as such and reduced to a singleton.
  • May be more common in older mares due to abnormal uterine changes or embryo abnormalities.

Clinical signs

  • May be none, and if the expelled material is not observed, the mare may abort without observation. In these cases the mare will fail to deliver a foal, without explanation.
  • In late pregnancy abortions, first stage labor may not be observed. Instead, in most cases, the mare expels the abortus standing and with little apparent effort or distress. The membranes are often delivered with the fetus although retained fetal membranes sometimes occur Placenta: retained.
  • ​Clinical signs of impending abortion are:
    • Premature mammary development or lactation   Mammary gland: teat - waxing up  .
    • Premature relaxation of the perineal ligaments.
    • Premature lengthening of the vulva, with or without mucopurulent or blood-tinged vulval discharge.
    • Dystocia is uncommon, except with late-term abortions (particularly of a dead fetus).
  • Mammary secretion electrolyte analysis may predict abortion. In normal mares mammary secretion potassium and calcium levels increase progressively towards parturition and sodium levels decrease from serum-like levels. When sodium and potassium have crossed over and calcium exceeds 10 mmol/l, foaling will occur within the next 24 h.
  • In aborting mares, sodium and potassium values may fluctuate and while calcium increases, it seldom reaches levels predictive of impending parturition.

Pathogenesis

  • Infectious.
  • Non-infectious.
  • The fetus may die in utero and be expelled, or may be born alive but be too compromised and/or premature to survive, eg if a twin.

Causes: non-infectious

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Causes: nutritional

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Causes: infectious

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Clinical signs

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Causes: viral

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General approach to management of an aborting mare

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Diagnostic procedures

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Cawdell-Smith A J, Todhunter K H, Perkins N R & Bryden W L (2013) Exposure of mares to processionary caterpillars ( Ochrogaster lunifer) in early pregnancy: An additional dimension to equine amnionitis and fetal loss. Equine Vet J 45 (6), 755-760 PubMed.
  • Cawdell-Smith A J et al (2012) Equine amnionitis and fetal loss: Mare abortion following experimetnal exposure to Processionary caterpillars (Ochrogaster lunifer). Equine Vet J 44 (3), 282-288 PubMed.
  • Marenzoni M L et al (2012) Causes of equine abortion, stillbirth and neonatal death in cental Italy. Vet Rec 170 (10), 262 PubMed.
  • Frazer G S (2007) Umbilical cord compromise as a cause of abortion. Equine Vet Educ 19 (10), 535-537 VetMedResource.
  • Jores J et al (2004) Isolation of Serratia marcescensfrom an equine abortion in Germany. Vet Rec 154 (8), 242-244 PubMed.
  • Ricketts S W, Barrelet A & Whitwell K E (2003) Equine abortion. Equine Vet Educ 15 (Suppl 6), 18-21 VetMedResource.
  • Smith K C et al (2003) A survey of equine abortion stillbirth and neonatal death in the UK from 1988 to 1997. Equine Vet J 35 (5), 496-501 PubMed.
  • Murray M J, del Piero F, Jeffrey S C, Davies M S, Furr M O, Dubovi E J & May J A (1998) Neonatal equine herpesvirus type 1 infection on a Thoroughbred breeding farm. J Vet Intern Med 12 (1), 36-41 VetMedResource.
  • Sutton G A, Viel L, Carman P S & Boag B L (1998) Pathogenesis and clinical signs of equine herpesvirus-1 in experimentally infected ponies in vivo. Can J Vet Res 62 (1), 49-55 PubMed.
  • Madic J, Hajsig D, Sostaric B, Curic S, Seol B, Naglic T & Cvetnic Z (1997) An outbreak of abortion in mares associated with Salmonella abortus equiinfection. Equine Vet J 29 (3), 230-233 PubMed.
  • Smith K C (1997) Herpesviral abortion in domestic animals. Vet J 153 (3), 253-268 PubMed.
  • Tengelsen L A, Yamini B, Mullaney T P, Bell T G, Patterson J S, Steficek B A, Fitzgerald S D, Kennedy F A, Slanker M R & Ramos-Vara J A (1997) A 12-year retrospective study of equine abortion in Michigan. J Vet Diagn Invest (3), 303-306 PubMed.
  • McCartan C G, Russell M M, Wood J N L & Mumford J A (1995) Clinical, serologic and virologic characteristics of an outbreak of paresis and neonatal foal disease due to equine herpes virus-1 on a stud farm. Vet Rec 136 (1), 7-12 PubMed.
  • Giles R C et al (1993) Causes of abortion, stillbirth, and perinatal death in horses - 3,527 cases (1986-1991). JAVMA 203 (8), 1170-1175 PubMed.

Other sources of information

  • Horserace Betting Levy Board (2016) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email: enquiries@hblb.org.uk; Website: http://codes.hblb.org.uk.

Organization(s)


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