Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins

J. A. Scare; D. M. Leathwick; C. W. Sauermann; E. T. Lyons; A. E. Steuer; B. A. Jones; M. Clark; M. K. Nielsen

doi:10.1016/j.ijpddr.2019.12.002

Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins

J. A. Scare, D. M. Leathwick, C. W. Sauermann, E. T. Lyons, A. E. Steuer, B. A. Jones, M. Clark, M. K. Nielsen

Veterinary Science

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient.

Original language	English
Pages (from-to)	28-34
Number of pages	7
Journal	International Journal for Parasitology: Drugs and Drug Resistance
Volume	12
DOIs	https://doi.org/10.1016/j.ijpddr.2019.12.002
State	Published - Apr 2020

Bibliographical note

Funding Information:
The field study was financially supported by Zoetis, and individual donors who supported Dr. Nielsen's latest crowdfunding campaign in support of the ‘Historic Parasitology Herds.’ We are grateful to the farm staff who provide continuous care for this special research herd. This study would not have been possible without the help from numerous very dedicated undergraduate students, namely Libby Wehling, Taylour Butler, Haley Zynda, Haley Anderson, Megan Bauer, Avery Martin, John Hines, Deanna Muscarello, Alyssa Carpenter, Morgan McVey, Samantha Naughton, Liz Bennett, and Aly McGuire.

Publisher Copyright:
© 2019

Keywords

Combination
Cyathostomin
Deworming
Equine
Moxidectin
Oxibendazole

ASJC Scopus subject areas

Parasitology
Infectious Diseases
Pharmacology (medical)

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.ijpddr.2019.12.002

Cite this

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title = "Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins",

abstract = "An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient.",

keywords = "Combination, Cyathostomin, Deworming, Equine, Moxidectin, Oxibendazole",

author = "Scare, {J. A.} and Leathwick, {D. M.} and Sauermann, {C. W.} and Lyons, {E. T.} and Steuer, {A. E.} and Jones, {B. A.} and M. Clark and Nielsen, {M. K.}",

note = "Funding Information: The field study was financially supported by Zoetis, and individual donors who supported Dr. Nielsen's latest crowdfunding campaign in support of the {\textquoteleft}Historic Parasitology Herds.{\textquoteright} We are grateful to the farm staff who provide continuous care for this special research herd. This study would not have been possible without the help from numerous very dedicated undergraduate students, namely Libby Wehling, Taylour Butler, Haley Zynda, Haley Anderson, Megan Bauer, Avery Martin, John Hines, Deanna Muscarello, Alyssa Carpenter, Morgan McVey, Samantha Naughton, Liz Bennett, and Aly McGuire. Publisher Copyright: {\textcopyright} 2019",

year = "2020",

month = apr,

doi = "10.1016/j.ijpddr.2019.12.002",

language = "English",

volume = "12",

pages = "28--34",

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AU - Scare, J. A.

AU - Leathwick, D. M.

AU - Sauermann, C. W.

AU - Lyons, E. T.

AU - Steuer, A. E.

AU - Jones, B. A.

AU - Clark, M.

AU - Nielsen, M. K.

N1 - Funding Information: The field study was financially supported by Zoetis, and individual donors who supported Dr. Nielsen's latest crowdfunding campaign in support of the ‘Historic Parasitology Herds.’ We are grateful to the farm staff who provide continuous care for this special research herd. This study would not have been possible without the help from numerous very dedicated undergraduate students, namely Libby Wehling, Taylour Butler, Haley Zynda, Haley Anderson, Megan Bauer, Avery Martin, John Hines, Deanna Muscarello, Alyssa Carpenter, Morgan McVey, Samantha Naughton, Liz Bennett, and Aly McGuire. Publisher Copyright: © 2019

PY - 2020/4

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AB - An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient.

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KW - Deworming

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KW - Moxidectin

KW - Oxibendazole

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Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

UN SDGs

Access to Document

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