Strongyle egg shedding and egg reappearance periods in horses with pituitary pars intermedia dysfunction.
Abstract: Pituitary pars intermedia dysfunction (PPID) is the most common endocrine disorder of older horses. Immune dysfunction in horses with PPID could increase susceptibility to infectious diseases, including strongyle infections; however, few data are available. The aim of this study was to determine if horses with PPID had increased strongyle faecal egg counts (FEC) compared with control horses, over a fourteen-week period in Victoria, Australia. Clinical signs and plasma adrenocorticotropic hormone (ACTH) concentrations were used to categorise horses into PPID (n=14) or control (n=31) groups. Faecal samples were collected for FEC determination prior to anthelmintic treatment, and fortnightly post-treatment for each horse. Generalised linear mixed modelling, using a gamma distribution, was used to compare differences between groups in the repeated measures study. The confounding variable of age was controlled for as a fixed effect. Following anthelmintic treatment, mean FEC was greater for the PPID group compared to the control group on day 56 (405 ± 756 eggs per gram [EPG] vs 40 ± 85 EPG, p=0.05) and day 70 (753 ±1598 EPG vs 82 ±141 EPG, p=0.04). There were no differences in mean FEC between groups on days 84 and 98. Cumulative FEC (day 14 to day 98) was significantly greater for the PPID horses than control horses (2118 ± 4016 EPG vs 798 ± 768 EPG, p<0.0001). Group egg reappearance period was shorter for PPID horses (day 56 post-anthelmintic treatment) compared to control horses (day 70) and 30% of the PPID horses reached a FEC threshold of >200 EPG on day 42, compared to 0% of control horses (p=0.02). These results suggest that the rate of a re-established patent infection between groups could be different due to a comprised immune response in PPID horses or differences in the host-parasite relationship regarding encysted stage larvae. However, despite differences between groups, some horses with PPID consistently had no detectable or low FEC (<200 EPG) during the study period. These findings highlight the importance of individual FEC monitoring to determine if anthelmintic treatment is required, in line with sustainable parasite management practices.
Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.
Publication Date: 2024-03-28 PubMed ID: 38603926DOI: 10.1016/j.vetpar.2024.110176Google Scholar: Lookup
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Summary
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The research investigates whether horses stricken with Pituitary pars intermedia dysfunction (PPID), a common endocrine disorder in older horses, have higher strongyle faecal egg counts (FEC) compared to healthy horses. The findings indicate that the PPID-afflicted horses presented higher FEC and also experienced a faster reoccurrence of the parasite eggs post-anthelmintic treatment. The researchers conclude that individual FEC monitoring is essential to determine the need for anthelmintic treatment.
Aim and Methodology
- The research goal was to compare the strongyle FEC in horses with PPID and control horses, across a fourteen-week period in Victoria, Australia.
- Horses were categorized into two groups, PPID (n=14) and control (n=31), based on their clinical signs and plasma adrenocorticotropic hormone (ACTH) levels.
- Faecal samples were collected before anthelmintic treatment and then every fortnight post-treatment for each horse.
- The researchers adjusted for age as a fixed effect to control for confounding variables, and they used a generalized linear mixed model with a gamma distribution to compare differences between the groups.
Results
- PPID horses showed a higher mean FEC compared to the control group on the 56th and 70th days post-treatment. There were no significant differences on the 84th and 98th days.
- Between the 14th and 98th days post-treatment, PPID horses exhibited greater cumulative FEC than the control horses.
- Re-occurrence of strongyle eggs was faster in the PPID group. 30% reached a FEC threshold of >200 eggs per gram (EPG) on the 42nd day, compared to none in the control group.
Interpretation and Conclusion
- The results indicate a potential immune compromise or host-parasite relationship in the case of PPID horses, leading to the quicker reemergence of strongyle eggs.
- Not all horses with PPID had consistently high FEC, with some presenting no detectable or low FEC throughout the study, emphasizing the importance of individual monitoring.
- These findings imply the necessity of personal FEC monitoring for determining anthelmintic treatment’s necessity, promoting sustainable parasite management practices.
Cite This Article
APA
Horner A, Bamford NJ, Stear MJ, Piedrafita D, Jabbar A, Hughes KJ, El-Hage CM, Preston S.
(2024).
Strongyle egg shedding and egg reappearance periods in horses with pituitary pars intermedia dysfunction.
Vet Parasitol, 328, 110176.
https://doi.org/10.1016/j.vetpar.2024.110176 Publication
Researcher Affiliations
- Institute of Innovation, Science and Sustainability, Federation University, Victoria 3350, Australia.
- Melbourne Veterinary School, The University of Melbourne, Parkville, Victoria 3010, Australia.
- School of Life Sciences, La Trobe University, Melbourne, Victoria 3086, Australia.
- Institute of Innovation, Science and Sustainability, Federation University, Victoria 3350, Australia.
- Melbourne Veterinary School, The University of Melbourne, Parkville, Victoria 3010, Australia.
- School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
- Melbourne Veterinary School, The University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: cmeh@unimelb.edu.au.
- Institute of Innovation, Science and Sustainability, Federation University, Victoria 3350, Australia. Electronic address: s.preston@federation.edu.au.
Conflict of Interest Statement
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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