A sustained release gel formulation of doramectin for control of lone star ticks (Acari: Ixodidae) and horn flies (Diptera: Muscidae) on cattle.
A gel formulation formed by incorporating technical doramectin into a 10% hydroxypropyl methylcellulose aqueous solution was used to subcutaneously inject steers at varying dosages. Doramectin serum concentration of steers receiving 600 microg (AI)/kg body weight declined from 21.9 ppb at 0.5 wk to below detectable at 8 wk postinjection. The 1,200 microg (AI)/kg injection resulted in serum concentrations of 29.1 ppb at 0.5 wk and declined to 0.5 ppb at 8 wk postinjection. Both the 600 and 1,200 microg (AI)/kg injections provided 100% inhibition of index of fecundity (IF) in adult lone star ticks, Amblyomma americanum L. (Acari: Ixodidae) through week 8, after which inhibition declined to 79.4 and 45.3%, respectively, during the 12th week posttreatment. For steers treated at 600 microg (AI)/kg, mortality of adult horn flies, Hematobia irritans L. (Diptera: Muscidae), declined from 16.9% during week 2 to 3.1% during week 7 postinjection. The blood from steers treated at 1,200 microg (AI)/kg resulted in a similar decline in mortality of blood fed adult horn flies from 29.4% during week 1 to 4.0% during week 7. The 600 microg (AI)/kg treatment provided complete control of larval horn flies in the manure for 9 wk, whereas the 1,200 microg (AI)/kg injection gave complete control for 14 wk posttreatment. The doramectin gel formulation provided long-lasting delivery of doramectin to cattle and extended control of lone star ticks and larval horn flies. Such a simple and inexpensive formulation could be useful in tick eradication programs by reducing the frequency of gathering cattle.
Lohmeyer
K H
KH
USDA-ARS, Knipling Bushland U.S. Livestock Insect Research Laboratory, 2700 Fredericksburg Road, Kerrville, TX 78028, USA. kim.lohmeyer@ars.usda.gov
Miller
J A
JA
Pound
J M
JM
Klavons
J A
JA
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D005782:Gels; D007279:Injections, Subcutaneous; D007306:Insecticides / Q000008:administration & dosage / Q000494:pharmacology; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D026863:Ixodidae / Q000187:drug effects*; D009117:Muscidae / Q000187:drug effects*; D009198:Myiasis / Q000517:prevention & control / Q000662:veterinary*; D013984:Tick Infestations / Q000517:prevention & control / Q000662:veterinary*; D013995:Time
D003692:Delayed-Action Preparations; D005782:Gels; D007306:Insecticides; D007559:Ivermectin; C084101:doramectin