Persistent efficacy of abamectin and doramectin against gastrointestinal nematodes of cattle.
OBJECTIVE
To assess the persistent activity of injectable formulations of abamectin and doramectin against gastrointestinal nematodes of cattle.


METHODS
Controlled slaughter study assessing residual efficacy.


METHODS
Nematode-free calves were treated with abamectin or doramectin (each at a dose of 200 micrograms/kg) and infections then induced with repeated doses of infective larvae of Trichostrongylus axei, Haemonchus placei, Ostertagia ostertagi and Cooperia species. The duration of challenge ranged from 14 to 28 days. The calves were slaughtered at either 38/39 or 45/46 days after the treatments and nematodes recovered from the gastro-intestinal tract.


RESULTS
Significant reductions in numbers of O ostertagi occurred for both abamectin and doramectin treatments (> 93%) relative to counts in untreated calves, when challenge was administered up to 21 days after treatment. For T axei and Cooperia spp significant reductions occurred when the challenge occurred for 14 days after treatment (99%). Although differences from untreated animals were not significant, the results for H placei suggested high efficacy (> 85%) for up to 21 days for doramectin and up to 28 days for abamectin.


CONCLUSIONS
There was no significant difference between abamectin and doramectin for any parasite at any challenge point, indicating that there is equivalent persistent activity of doramectin and abamectin against important gastrointestinal nematodes of cattle.
Rolfe
P F
PF
NSW Agriculture, Elizabeth Macarthur Agricultural Institute, Camden.
Dawson
K L
KL
Soll
M D
MD
Nichols
G K
GK
Ryan
W G
WG
D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D004064:Digestive System / Q000469:parasitology; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000469:parasitology; D006188:Haemonchiasis / Q000188:drug therapy / Q000662:veterinary; D006189:Haemonchus / Q000302:isolation & purification; D007411:Intestinal Diseases, Parasitic / Q000188:drug therapy / Q000662:veterinary; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008297:Male; D009348:Nematoda / Q000302:isolation & purification; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*; D010028:Ostertagia / Q000302:isolation & purification; D010029:Ostertagiasis / Q000188:drug therapy / Q000662:veterinary; D010270:Parasite Egg Count; D013997:Time Factors; D014253:Trichostrongylosis / Q000188:drug therapy / Q000662:veterinary; D014254:Trichostrongylus / Q000302:isolation & purification
D000871:Anthelmintics; C048324:abamectin; D007559:Ivermectin; C084101:doramectin