Infection rates of Amblyomma americanum (Acari: Ixodidae) by Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) and prevalence of E. chaffeensis-reactive antibodies in white-tailed deer in southern Indiana, 1997.
To monitor the percentage and stability of Ehrlichia chaffeensis-infected ticks in southern Indiana over time, pools of Amblyomma americanum (L.) ticks were screened for infection in southern Indiana for a 2nd time. Nested polymerase chain reaction (with 6% DMSO included only in the 2nd reaction) was performed on 920 ticks in pools of 5 individuals from 9 sites (5 sites previously examined and 4 new ones) in 6 counties. The average minimum infection rate for all sites for 1997 was 1.6%, lower than that of 4.9% previously observed for 1995. However, when only the 5 sites that were positive for infected ticks in 1995 were reexamined, the average minimum infection rate was even more disparate (1.4% in 1997 and 5.1% in 1995). To correlate the presence of infected ticks with the presence of exposed deer, which serve as a reservoir, dried blood samples collected from hunter-killed deer at 2 locations in southern Indiana were tested for E. chaffeensis-reactive antibodies using an indirect immunofluorescent assay. Antibodies were detected in 45 and 47% of 98 samples examined from the 2 stations. These data provide support to our previous report of a population of E. chaffeensis-infected A. americanum in southern Indiana and the high proportion of deer previously exposed to E. chaffeensis suggests a stable maintenance of E. chaffeensis in this tick-vertebrate zoonotic system.
Steiner
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Department of Biology, Ball State University, Muncie, IN 47306, USA.
Pinger
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Vann
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D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D003670:Deer / Q000276:immunology / Q000382:microbiology*; D018469:Ehrlichia chaffeensis / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D019084:Fluorescent Antibody Technique, Indirect; D007196:Indiana; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D013987:Ticks / Q000382:microbiology*
D000907:Antibodies, Bacterial