Reduced Abundance of Ixodes scapularis (Acari: Ixodidae) and the Tick Parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) with Reduction of White-Tailed Deer

• Published in: Journal of medical entomology Vol. 40; no. 5; pp. 642 - 652
• Main Authors: Stafford, Kirby C., Denicola, Anthony J., Kilpatrick, Howard J.
• Format: Journal Article
• Language: English
• Published: Lanham, MD Entomological Society of America 01-09-2003
• Subjects: Animals; Biological and medical sciences; Connecticut; deer; Deer - parasitology; deer reduction; Fundamental and applied biological sciences. Psychology; Geography; host density; host-parasite relationships; Ixodes - growth & development; Ixodes - pathogenicity; Ixodes scapularis; Ixodiphagus hookeri; Larva; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Odocoileus virginianus; parasitism; parasitoid; parasitoids; POPULATION AND COMMUNITY ECOLOGY; population density; Population Growth; population size; temporal variation; threshold density; tick; Tick Infestations - epidemiology; Tick Infestations - veterinary; ticks; Vectors. Intermediate hosts; Wasps - parasitology; Connecticut; United States; North America; America; Host parasite relation; deer reduction; Prevalence; Insecta; Ixodes scapularis; Acari; Chalcidoidea; Ixodiphagus hookeri; Vector; Ixodidae; Ungulata; Odocoileus virginianus; Parasitiformes; tick; Multiyear variation; Population decline; Interannual variation; Arachnida; Vertebrata; Mammalia; Parasitoid; Encyrtidae; Ixodida; Arthropoda; Animal; Cervidae; Population dynamics; Parasitism; Artiodactyla; Hymenoptera; Invertebrata; Population density
• ISSN: 0022-2585; 1938-2928
• DOI: 10.1603/0022-2585-40.5.642

The principal vector for the pathogens of Lyme disease, human granulocytic ehrlichiosis, and human babesiosis is the tick Ixodes scapularis Say. A chalcid wasp, Ixodiphagus hookeri, in the family Encyrtidae parasitizes populations of the tick on several islands or other geographically isolated sites in New England with high densities of these ticks and white-tailed deer (Odocoileus virginianus), the principal host for adult I. scapularis. Deer densities were reduced at a forested tract in Bridgeport and the Bluff Point Coastal Reserve in Groton, Connecticut, from levels exceeding 90 animals per km2 in 1992 (Bridgeport) and 1994 (Bluff Point) to 17 and 10 animals per km2, respectively, by fall 2001. Tick densities declined with sustained reductions in the population of white-tailed deer. Similarly, prevalence of tick parasitism by Ixodes hookeri declined at both sites from 30 to 25% to <1.0% and was significantly correlated with previous year’s deer density at both sites (rs = 0.933 and rs = 0.867, P ≤ 0.0001) and with nymphal tick densities at Bridgeport (rs = 0.867, P ≤ 0.0001), but was not as well correlated with tick densities in Groton. The virtual disappearance of I. hookeri in this study corresponds with a lack of I. hookeri in mainland I. scapularis at comparable deer and tick densities, suggesting that there is a threshold deer density of ≈10–20/km2, with corresponding tick densities necessary for I. hookeri to successfully parasitize I. scapularis.