Management of drug-resistant cyathostominosis on a breeding farm in central North Carolina.
BACKGROUND
Possible anthelmintic resistance on a breeding farm where a rapid rotation anthelmintic programme had been implemented for 9 years was investigated. Cyathostomins resistant to fenbendazole and pyrantel were documented by faecal worm egg count reduction test (FWECRT).


OBJECTIVE
To 1) manage small strongyle transmission in a herd of horses in which resistance to both pyrantel pamoate and fenbendazole was identified and thereby reduce the risk of clinical disease in the individual animal, 2) monitor the change in resistance patterns over time and 3) monitor the efficacy of ivermectin over the study period.


METHODS
Targeted ivermectin treatment of horses on the farm was instituted for mature horses with faecal worm egg counts (FWEC) > 200 eggs/g (epg) and for horses < age 2 years with FWEC > 100 epg.


RESULTS
Over a 30 month period, targeted ivermectin treatment achieved acceptable control in mares, as judged by FWEC, and improved control of patent cyathostome infection in consecutive foal crops. Egg reappearance time (ERT) after treatment with ivermectin was < 8 weeks in mares and foals more frequently in the second year of the study than in the first year. Numbers of anthelmintic treatments were reduced by 77.6 and 533% in the mare and foal group, respectively.


CONCLUSIONS
Targeted ivermectin treatment may be an economically viable method of managing multiple drug resistant cyathostominosis.


CONCLUSIONS
Use of ivermectin should be monitored closely for development of resistance.
Little
D
D
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27606, USA.
Flowers
J R
JR
Hammerberg
B H
BH
Gardner
S Y
SY
D000818:Animals; D000969:Antinematodal Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004351:Drug Resistance; D018432:Drug Resistance, Multiple; D005243:Feces / Q000469:parasitology; D005260:Female; D005273:Fenbendazole / Q000494:pharmacology / Q000627:therapeutic use; D006736:Horses; D007411:Intestinal Diseases, Parasitic / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D007559:Ivermectin / Q000494:pharmacology* / Q000627:therapeutic use; D009657:North Carolina; D010270:Parasite Egg Count / Q000662:veterinary; D021261:Parasitic Sensitivity Tests / Q000662:veterinary; D011715:Pyrantel / Q000494:pharmacology / Q000627:therapeutic use; D013319:Strongyle Infections, Equine / Q000188:drug therapy* / Q000469:parasitology; D013320:Strongyloidea / Q000187:drug effects*; D016896:Treatment Outcome
D000969:Antinematodal Agents; D011715:Pyrantel; D005273:Fenbendazole; D007559:Ivermectin