A comparative analysis of PCR-based detection methods for avian malaria.

Here, 4 polymerase chain reaction (PCR) assays are compared to test for the presence of avian malaria, including both the Plasmodium and Haemoproteus genera, in 29 different species of African rainforest birds. Two of these PCR assays use primer sets that amplify fragments of the cytochrome b (cyt b) gene of Plasmodium; the other 2 target the 18S ribosomal subunit gene. These PCR assays were performed using genomic DNA extracted from blood and subsequently compared with the results obtained by microscopic examination of blood smears taken from the same individuals. The 2 primer sets amplifying the cyt b gene were found to perform more reliably than those that target the 18S rRNA gene and yielded a substantial number of positive samples that were undetected by blood smear analysis. Of all the individuals screened by PCR, 40% tested positive for avian malaria, whereas 27% tested positive by blood smear analysis. Although sequence variation in the parasites may prohibit the specific alignment of primers and the subsequent PCR amplification of some individuals, PCR, once optimized, is faster, cheaper, and more reliable than blood smear analysis for large-scale screening.