Investigation of the Bi-Weekly Administration of Diclazuril on the Antibody Kinetics to Sarcocystis Neurona in Healthy Horses.
Abstract: The aim of this study was to determine if bi-weekly administration of diclazuril at half the label dose would reduce seroprevalence and magnitude of titers to S. neurona in healthy horses naturally exposed to the apicomplexan protozoal parasite. 12 healthy adult horses were moved from a low-risk exposure to a farm with high exposure rate to S. neurona in their horse population. The horses were randomly assigned to either a treatment or a control group. Treatment consisted in the administration of half the label dose (0.5 mg/kg) of diclazuril (Protazil) pelleted top dress twice weekly (every 3-4 days) for 12 months. Prior to initiation of treatment and monthly thereafter, blood was collected for the detection of antibodies to S. neurona using a quantitative immunoassay. Further, trough plasma diclazuril levels were determined every 60 days. All 20 horses remained healthy during the entire study period. Seroprevalence to S. neurona decreased initially in the treatment group to 50% at 30 days post-treatment commencement. This was followed by a slow increase in seroprevalence in the treatment group before reaching 100% in both groups by 90 days post-treatment commencement. The seroprevalence remained 100% in both groups from 90 to 360 study days. While titer distribution between the two groups was similar at study commencement, treated horses had significantly lower titers throughout the treatment period (P < 0.05). All treated study horses had detectable plasma trough diclazuril levels at the 6 time points and the levels were above the concentration known to inhibit S. neurona in vitro (1.0 ng/mL). The administration of diclazuril pelleted top dress at half the label dose twice weekly was able to maintain low titers to S. neurona in healthy adult horses naturally exposed to the protozoal parasite. Further, trough diclazuril levels were in excess of the minimal concentration known to inhibit S. neurona.
Copyright © 2021. Published by Elsevier Inc.
Publication Date: 2021-07-16 PubMed ID: 34416990DOI: 10.1016/j.jevs.2021.103713Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
- Veterinary
- Research Support
- Non-U.S. Gov't
Summary
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This research assessed the impact of a bi-weekly, reduced-dose delivery of the drug Diclazuril on healthy horses exposed to the parasite Sarcocystis neurona. The study indicates that the drug may limit the proliferation of this parasite.
Study design and Participants
- The study involved 12 healthy adult horses which were transferred from a farm with a low incidence of S. neurona infestation to one with higher exposure levels.
- These horses were arbitrarily separated into a control group and a treatment group.
- Both groups were monitored for a period of 12 months, during which they were regularly tested for antibody levels against S. neurona.
Treatment Administration
- The horses in the treatment group received a bi-weekly dose of Diclazuril at half the standard recommended dosage.
- This treatment plan was maintained throughout the study period.
- In addition to monitoring the exposure levels and health of the horses, the researchers also quantified the level of Diclazuril in the subjects’ plasma every 60 days.
Findings
- All of the subjects remained healthy throughout the study.
- Initially, only half of the treatment group developed antibodies to the parasite, but this rose to 100% within 90 days of commencing the treatment. This level remained constant for the duration of the study.
- However, the horses which received Diclazuril treatment had significantly lower antibody titers throughout the study, indicating a reduced level of parasitic activity within their systems.
- At all points measured, Diclazuril levels within the plasma of the treated subjects were higher than the minimum concentration needed to inhibit S. neurona, providing further evidence of the treatment’s effectiveness.
Conclusion
- The research suggests that the administration of Diclazuril at half the label dose, twice weekly, can help maintain low antibody titers to S. neurona.
- Its effectiveness is also indicated by measured plasma levels of Diclazuril, which remained consistently higher than the minimum concentration known to inhibit S. neurona.
- As such, this method of administration might be effective for combating S. neurona infestation in healthy adult horses.
Cite This Article
APA
Pusterla N, James K, Bain F, Barnett DC, Chappell D, Gaughan E, Craig B, Schneider C, Vaala W, Papich M.
(2021).
Investigation of the Bi-Weekly Administration of Diclazuril on the Antibody Kinetics to Sarcocystis Neurona in Healthy Horses.
J Equine Vet Sci, 104, 103713.
https://doi.org/10.1016/j.jevs.2021.103713 Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California. Electronic address: npusterla@ucdavis.edu.
- Department of Obstetrics, Gynecology and Reproductive Biology, Massachusetts General Hospital, Boston, Massachusetts.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- Merck Animal Health, Madison, New Jersey.
- College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina.
MeSH Terms
- Animals
- Antibodies
- Horse Diseases
- Horses
- Kinetics
- Nitriles
- Sarcocystis
- Sarcocystosis / veterinary
- Seroepidemiologic Studies
- Triazines
Citations
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