Identification of mosquito bloodmeal source by terminal restriction fragment length polymorphism profile analysis of the cytochrome B gene.

Previous studies have shown that polymerase chain reaction (PCR) heteroduplex analysis (HDA) of the cytochrome B (cytb) gene is useful in identifying mosquito bloodmeals derived from avian hosts. However, interpretation of PCR-HDA gels is performed visually, which can make it difficult to analyze large numbers of specimens and to compare results between laboratories. We investigated the utility of a terminal restriction fragment length polymorphism (T-RFLP) assay to analyze cytb PCR products. PCR was performed on 123 blood or tissue samples from 55 avian, 13 mammalian, and one amphibian species by using end-labeled primers to amplify a 358-bp segment of cytb. Each PCR product was sequenced to determine predicted terminal restriction fragment (TRF) profiles. Additionally, experimental TRFs were determined by sizing fragments from restriction endonuclease digests with capillary electrophoresis. A Web-based searchable database was created to compare unknown mosquito bloodmeal TRF profiles against sequence-predicted and experimentally derived terminal fragment lengths of known vertebrates. The predictive value of experimental profiles was found to be accurate to the species level for 67 of 69 species (97%). Fifty-nine field-collected mosquitoes were tested to determine the bloodmeal source using the T-RFLP method. The bloodmeal source from 50 of these mosquitoes was identified by comparing the TRF profile of the unknown source against the cytochrome B database. The bloodmeal source from the remaining nine mosquitoes was not identified as no known profile matched the experimentally derived profile. T-RFLP analysis is a highly reproducible technique and the searchable TRF database is continually being expanded to include additional species from diverse geographic areas.