Term of Award

Summer 1986

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Committee Chair

James H. Oliver, Jr.

Committee Member 1

Sturgis McKeever

Committee Member 2

Richard L. Osburn

Abstract

Ivermectin was injected into hosts and evaluated for effectiveness against the argasid tick, Ornithodoros parkeri (Cooley) and the chicken mite Dermanyssus gallinae (DeGeer). Ornithodoros parkeri second stage nymphs (N2s), fed on ivermectin injected mice, showed a marked increase in mortality at a dose between 0.100, and 0.200 yg/g host body weight. For adults of O. parkeri and D. gallinae, a dose between 0.400 and 0.500 pg/g host body weight was necessary for control. These findings support data reported on other tick species, but differ with those reported for the northern fowl mite. Further testing narrowed the effective range for O. parkeri adults to between 0.425 and 0.450 pg/g host body weight. The time interval (4, 8, & 24 hours) between ivermectin injection of the host and tick feeding had only a slight influence on the overall effectiveness of the drug. Doses of 0.0125 to 0.1000 pg/g body weight produced no visible effect on gross morphology of internal structures (reproductive system and synganglion) or histological changes of the reproductive system; they also do not affect fecundity or hatchability. Contrary to reports of irreversibility of effects of ivermectin on GABA mediated neurotransmission, many ivermectin paralyzed ticks recovered partial mobility over time.

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