Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 21, 1996
Publication Date: N/A
Interpretive Summary: Lyme disease is a tick-borne ailment that can seriously debilitate humans. Its principal vector in the eastern U.S. is the black-legged tick, which in the adult stage waits on vegetation for passing hosts. Previous laboratory studies suggested that substances rubbed from external leg glands of white-tailed deer may influence host-seeking adult female black-legged ticks in their selection of host-ambushing sites. In a field study, involving the release of wild black-legged ticks in host- free enclosures, we showed that under natural conditions adult ticks of both sexes used simulated ambush sites treated with gland-associated substances rather than untreated ambush sites. Also, in laboratory tests female black-legged ticks responded similarly to substances rubbed from preorbital glands of deer. These results help explain how unfed black- legged ticks, and probably other species of ticks as well, find hosts, and also explain the presence of host-seeking ticks along animal trails. Researchers will benefit from this knowledge, which may ultimately be used in developing strategies for reducing the risk of tick bites.
Technical Abstract: In a field test released wild adult blacklegged ticks, Ixodes scapularis Say, of both sexes exhibited an arrestant response to substances associated with external glands on the legs of white-tailed deer, Odocoileus virginianus (Zimmermann), their principal host. Substances rubbed from the pelage covering tarsal and interdigital glands were applied to artificial vantage points simulating vegetation on which I. scapularis adults wait for host contact. A combination of tarsal substances (applied to the apex of the simulated vantage point) and interdigital gland substances (applied to the horizontal base) elicited a greater response than either treatment alone. A minimal response was observed on untreated vantage points. In laboratory bioassays using glass tubing as vantage points, substances associated with preorbital glands of deer elicited a strong arrestant response among I. scapularis females, whereas samples rubbed from the forehead, back and a nonglandular area on deer tarsi evoked weak arrestant responses. These results support the hypothesis that the kairomonal properties of host-generated residues, either in conjunction with or in lieu of the effects of carbon dioxide, help account for the prevalence of host-seeking ticks along animal trails.