title: Control of lone star ticks (Acari: Ixodidae) on Spanish goats and white-tailed deer with orally administered ivermectin.
abstract: Ivermectin administered orally to Spanish goats, Capra hircus (L.), or to white-tailed deer, Odocoileus virginianus (Zimmerman), was highly effective against lone star ticks, Amblyomma americanum (L.). For Spanish goats, daily oral doses of 20 micrograms/kg resulted in greater than or equal to 2 ppb ivermectin in the blood. This level was sufficient to cause greater than 95% reduction of estimated larvae from feeding ticks. A bioassay with horn flies, Haematobia irritans (L.), was developed to estimate oral intake of ivermectin. Probit analysis of dose-mortality data indicated that a 50% reduction in adult horn fly emergence can be expected when the manure from goats treated orally with ivermectin at 10, 20, 35, and 50 micrograms/kg/d was mixed with untreated cow manure at a rate of 0.345, 0.110, 0.100, and 0.092%, respectively. In studies with white-tailed deer, daily oral doses of 35 and 50 micrograms/kg/d provided 100% control of adult and about 90% control of nymphs that were placed on treated fawns. A single oral dose of 50 micrograms/kg gave greater than 90% control of adult and nymphal ticks attached to treated fawns at the time of drug administration and 70% control of ticks placed on treated deer three days thereafter. When ticks were placed on fawns treated with a single dose of ivermectin (50 micrograms/kg) the engorgement period was longer, ticks were lighter in weight, and females laid fewer eggs than ticks detaching from control fawns. A single oral dose of ivermectin at 20 micrograms/kg prevented about 60% of the adult and nymphal ticks attached at the time of drug administration from engorging, but did not affect other ticks placed on the animals after treatment.
authors.forename: J A
authors.initials: JA
authors.lastname: Miller
authors.forename: G I
authors.initials: GI
authors.lastname: Garris
authors.forename: J E
authors.initials: JE
authors.lastname: George
authors.forename: D D
authors.initials: DD
authors.lastname: Oehler
mesh_terms: D000284:Administration, Oral; D000818:Animals; D003670:Deer / Q000469:parasitology*; D005260:Female; D015511:Goat Diseases / Q000517:prevention & control*; D006041:Goats; D007559:Ivermectin / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D013984:Tick Infestations / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D007559:Ivermectin