Ticks (Acari: Ixodidae) and spirochetes (Spirochaetaceae: Spirochaetales) recovered from birds on a Georgia Barrier Island

From September 1997 through July 1999, 300 individuals and 46 species of birds were mist-netted and screened for ticks and spirochetes on St. Catherine's Island, Liberty County, GA. Seventy-six (25%) of the birds were parasitized by a mean intensity of 4.6 ticks. Seasonally, more birds were infested with ticks during the summer (50% in 1998, 34% in 1999) than in spring (15% in 1998, 11% in 1999) or fall (21% in 1997, 20% in 1998), mainly because of severe infestations on some birds by immature stages of the lone star tick, Amblyomma americanum (L.), during this season. Eight species of ticks were recovered from 14 species of birds during this study: A. americanum (74 nymphs, 168 larvae); the blacklegged tick, Ixodes scapularis Say (11 nymphs, 28 larvae), the Gulf Coast tick, Amblyomma maculatum Koch (two nymphs, 29 larvae); Ixodes minor Neumann (16 larvae); the rabbit tick, Haemaphysalis leporispalustris (Packard) (one nymph, 14 larvae); the bird tick Ixodes brunneus Koch (two larvae); the American dog tick, Dermacentor variabilis (Say) (one nymph); and Ixodes affinis Neumann (one larva). The Carolina wren was parasitized by more species of ticks (seven) than any other bird species, followed by the northern cardinal (five), white-throated sparrow (four) and painted bunting (three). Spirochetes were isolated in BSK II medium from one tick (a nymphal A. americanum) and from skin biopsies of 12 (4%) of the individual birds (three downy woodpeckers, three northern waterthrushes, two Carolina wrens, one American redstart, one pine warbler, one Swainson's thrush, and one white-eyed vireo) all in fall 1997. This concentrated phenology of spirochete isolations might reflect periodic amplification or recrudescence of spirochetes in reservoir avian hosts.