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Equine veterinary journal2013; 45(6); 755-760; doi: 10.1111/evj.12044

Exposure of mares to processionary caterpillars (Ochrogaster lunifer) in early pregnancy: an additional dimension to equine amnionitis and fetal loss.

Abstract: Equine amnionitis and fetal loss (EAFL) is an unusual form of abortion in mid- to late-gestation mares, first identified in Australia in 2004. It has been shown that both whole processionary caterpillars (Ochrogaster lunifer) and their shed exoskeletons can induce abortion in mares during midgestation. These abortions exhibited gross pathology and bacteriology results consistent with field cases of EAFL. Objective: To determine whether exposure of mares to the shed exoskeletons of processionary caterpillars can induce abortion in the preplacentation (<35 days' gestation) and early placentation (45-60 days) stages of pregnancy. Methods: In vivo experimental study. Methods: Mares less than 35 days' gestation and between 45 and 60 days' gestation were exposed to a slurry of shed processionary caterpillar exoskeletons by nasogastric intubation. Mares were monitored by clinical examination daily. Transrectal ultrasonography was performed daily (control and treated preplacentation mares, treated early placentation mares) or every second day (control early placentation mares). Uterine swabs were collected from mares that aborted. All live foals underwent a clinical examination. Placentas were examined, with sampling for bacteriology and histopathology if appropriate. Results: Abortions occurred in treated mares in both experiments without signs of impending abortion. One mare aborted in the embryonic stage experiment and 2 in the early placentation experiment. Embryonic and fetal death was detected on transrectal ultrasonography prior to abortion. In the early placentation experiment, one foal was born 5 weeks preterm and was very small, with laxity of the tendons in all limbs. Enteric or environmental bacteria, consistent with EAFL, were isolated from the mares that aborted. Focal mucoid placentitis lesions were present on the placentas of 2 treated mares, one from each experiment. Conclusions: Processionary caterpillar exposure may be associated with EAFL-related embryonic and early fetal loss in mares. Processionary caterpillars may also play a role in the occurrence of focal mucoid placentitis.
© 2013 EVJ Ltd.
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Publication Date: 2013-03-04 PubMed ID: 23452012DOI: 10.1111/evj.12044Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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This study explores the possibility that exposure to processionary caterpillars and their shed exoskeletons, could affect early stages of pregnancy in mares leading to Equine Amnionitis and Fetal Loss (EAFL). The researchers found that such exposure could induce abortion without any early signs and could also contribute to other issues like focal mucoid placentitis in the mares.

Objective and Approach

  • The primary objective of this study was to ascertain whether exposure to processionary caterpillars can cause abortion in mares during the early stages of gestation. The researchers carried out in-vivo experiments to determine this.
  • Mares were exposed to a mixture of shed exoskeletons of processionary caterpillars through nasogastric intubation. These mares, less than 35 days’ gestation and between 45 and 60 days’ gestation, were observed daily by conducting clinical examinations and transrectal ultrasonography.
  • Uterine swabs were collected from mares that underwent abortion. Clinical examination was performed on all live foals and placentas were closely examined and sampled for bacteriology and histopathology if necessary.

Findings

  • The results indicated that EAFL could indeed be induced through exposure to processionary caterpillars. Abortion was noticed in mares that were part of the study without any early signs of the same.
  • The researchers found embryonic and fetal deaths before abortion, as observed through transrectal ultrasonography. One foal was born preterm five weeks early and was very small with limpness in all limbs, again indicating the negative impact of caterpillar exposure.
  • Bacteriological analysis revealed the presence of enteric or environmental bacteria, which are consistent with EAFL, from the mares that had abortions.
  • There were cases of mucoid placentitis in two mares, one from each experiment. This suggests that exposure to processionary caterpillars could also lead to this placental infection and inflammation.

Conclusions

  • The study concluded that exposure to processionary caterpillars can lead to EAFL-associated embryonic and early fetal loss in mares.
  • Moreover, processionary caterpillars may also be involved in the incidence of focal mucoid placentitis in mares exposed to the caterpillars.

Cite This Article

APA
Cawdell-Smith AJ, Todhunter KH, Perkins NR, Bryden WL. (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. https://doi.org/10.1111/evj.12044

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 45
Issue: 6
Pages: 755-760

Researcher Affiliations

Cawdell-Smith, A J
  • Equine Research Unit, School of Agriculture and Food Sciences, The University of Queensland, Australia.
Todhunter, K H
    Perkins, N R
      Bryden, W L

        MeSH Terms

        • Aborted Fetus
        • Abortifacient Agents / toxicity
        • Abortion, Veterinary
        • Animals
        • Australia
        • Chorioamnionitis / chemically induced
        • Chorioamnionitis / veterinary
        • Female
        • Fetal Death / chemically induced
        • Fetal Death / veterinary
        • Horse Diseases / chemically induced
        • Horses
        • Larva
        • Moths / physiology
        • Pregnancy
        • Pregnancy Outcome / veterinary

        Citations

        This article has been cited 4 times.
        1. Chapuis RJJ, Ragno VM, Ariza CA, Movasseghi AR, Sayi S, Uehlinger FD, Montgomery JB. Septic fibrinous pericarditis in 4 horses in Saskatchewan following an outbreak of forest tent caterpillars in 2017. Can Vet J 2020 Jul;61(7):724-730.
          pubmed: 32655155
        2. Perkins LE, Cribb BW, Pagendam DE, Zalucki MP. Variation in Morphology and Airborne Dispersal of the Urticating Apparatus of Ochrogaster lunifer (Lepidoptera: Notodontidae), an Australian Processionary Caterpillar, and Implications for Livestock and Humans. J Insect Sci 2019 Nov 1;19(6).
          doi: 10.1093/jisesa/iez112pubmed: 31782508google scholar: lookup
        3. Begg AP, Todhunter K, Donahoe SL, Krockenberger M, Slapeta J. Severe amoebic placentitis in a horse caused by an Acanthamoeba hatchetti isolate identified using next-generation sequencing. J Clin Microbiol 2014 Aug;52(8):3101-4.
          doi: 10.1128/JCM.01071-14pubmed: 24829227google scholar: lookup
        4. Hardefeldt L, Thomas K, Page S, Norris J, Browning G, El Hage C, Stewart A, Gilkerson J, Muscatello G, Verwilghen D, van Galen G, Bauquier J, Cuming R, Reynolds B, Whittaker C, Wilkes E, Clulow J, Burden C, Begg L. Antimicrobial prescribing guidelines for horses in Australia. Aust Vet J 2025 Dec;103(12):781-889.
          doi: 10.1111/avj.70003pubmed: 40903020google scholar: lookup
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