Sensitive measure of prevalence and parasitaemia of haemosporidia from European blackbird (Turdus merula) populations: value of PCR-RFLP and quantitative PCR
Haemosporidian parasites are common in birds in which they act as an important selective pressure. While most studies so far have focused on the effect of their prevalence on host life-history traits, no study has measured the effect of parasitaemia. We developed molecular methods to detect, identify and quantify haemosporidia in 2 natural populations of the Blackbird Turdus merula. Three different parasite genotypes were found – 1 Haemoproteus and 2 Plasmodium. A PCR-RFLP screening revealed that only approximately 3% of blackbirds were free of parasites, compared to the 34% of uninfected birds estimated by blood smear screening. A quantitative PCR (q-PCR) assay revealed a weaker parasitaemia in microscopically undetected parasites compared to microscopically detected ones. Large parasitaemia differences were found between parasite species, suggesting either differing parasite life-histories or host resistance. Parasitaemias were also weaker in male hosts, and in urban habitats, suggesting that both host factors (e.g. immunity) and habitat characteristics (e.g. vector availability) may modulate parasite density. Interestingly, these differences in parasitaemia were comparable to differences in parasite prevalence estimated by smear screening. This suggests that previous results obtained by smear screening should be reinterpreted in terms of parasitaemia instead of parasite prevalence.(Received April 20 2006)
(Revised June 13 2006)
(Accepted June 15 2006)
(Published Online September 4 2006)
Key Words: Plasmodium; Haemoproteus; Turdus merula; real-time PCR; PCR-RFLP; field populations; parasitaemia; prevalence.
c1 Equipe Ecologie Evolutive, UMR CNRS 5561 Biogéosciences, Université de Bourgogne, 6 Bd Gabriel, 21000 Dijon, France. Tel:+33 (0)3 80 39 62 06. Fax:+33 (0)3 80 39 62 31. E-mail: email@example.com