Efficacy of eprinomectin against Hypoderma spp in cattle.
OBJECTIVE
To determine the efficacy of a topical formulation of eprinomectin against natural infestations of first (L1)-stage, and second and third (L2/L3)-stage larvae of Hypoderma spp.


METHODS
140 approximately 6- to 18-month-old cattle of various breeds.


METHODS
Cattle, selected from herds with high prevalence of Hypoderma infestation, were treated in 4 experiments: within each replicate, 1 animal received eprinomectin at a dosage of 500 micrograms/kg of body weight against first-stage larvae (L1). The second animal received the same treatment against second or third-stage larvae (L2/L3). The third animal served as an untreated control. In a fifth experiment, visible warbles were treated on half of the cattle. Remaining cattle served as vehicle-treated controls. In 1 experiment, warbles were examined from time of treatment until all lesions were resolved. In 4 experiments, emerging Hypoderma larvae were recovered, speciated, and enumerated, and viability was determined.


RESULTS
Eprinomectin (500 micrograms/kg) efficacy was complete against L1. Hypoderma L2/L3 eradication approached 100% efficacy (1 live larva was recorded). Warbles in treated cattle resolved in a significantly shorter time than did those in controls. Adverse reactions related to treatment were not observed in any of the trials.


CONCLUSIONS
Eprinomectin (500 micrograms/kg) applied topically was safe and highly efficacious for treatment of all larval stages of Hypoderma spp in these trials.


CONCLUSIONS
Attributes of eprinomectin besides antiparasite efficacy allow treatment of all classes of cattle with no need for meat or milk withdrawal.
Holste
J E
JE
Merck & Co Inc, Rahway, NJ 07065, USA.
Colwell
D D
DD
Kumar
R
R
Lloyd
J E
JE
Pinkall
N P
NP
Sierra
M A
MA
Waggoner
J W
JW
Langholff
W K
WK
Barrick
R A
RA
Eagleson
J S
JS
D000287:Administration, Topical; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases; D004175:Diptera; D005260:Female; D007000:Hypodermyiasis / Q000188:drug therapy / Q000662:veterinary*; D007306:Insecticides / Q000008:administration & dosage / Q000627:therapeutic use*; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use; D007814:Larva; D008297:Male
D007306:Insecticides; D007559:Ivermectin; C101434:eprinomectin