J Med Entomol
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The ability of Ixodes scapularis Say and Amblyomma americanum (L.) to remain on drags, once acquired, was tested in sparse and dense shrub layer vegetation. When placed on bottoms of drags, adults of both species remained attached for distances three to four times greater in sparse vegetation compared with dense vegetation. When attached to the tops of drags, the differences in retention of ticks on drags between vegetation densities were significant only for A. americanum. In dense vegetation, drags should be checked at 10-m intervals, whereas in sparse vegetation this distance can be extended to 20 m without significant loss of acquired ticks.
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Field-collected house finches of mixed sex and age were infected experimentally with either western equine encephalomyelitis (WEE) or St. Louis encephalitis (SLE) viruses during the summer or fall of 1998 and maintained over the winter under ambient conditions. To detect natural relapse during the spring, 32 birds were bled weekly from February through June 1999, and then necropsied 1 yr after infection to detect chronic infections using a reverse transcription polymerase chain reaction (RT-PCR). ⋯ Collectively, our results indicated that a low percentage of birds experimentally infected with WEE or SLE developed chronic infections in the spleen or lung that could be detected by RT-PCR, but not by plaque assay. Birds did not appear to relapse naturally or after immunosuppression. The rapid decay of SLE, but not WEE, antibody may allow the relapse of chronic infections of SLE, but not WEE, to produce viremias sufficiently elevated to infect mosquitoes.