Determinants of prevalence and intensity of infection with malaria parasites in the Blue Tit

Abstract

Parasite species are usually specialists utilising specific host species, but parasite assemblages may differ substantially even between populations of the same species and show seasonal and annual fluctuations. Host characteristics such as individual age and sex may also affect parasite species composition and abundance. Here, we report the occurrence of malaria parasites in the Blue Tit (Cyanistes caeruleus) inhabiting Gotland (Sweden) across 5 years. Using PCR-based techniques, we found eight cytochrome b lineages belonging to genus Plasmodium (pTURUD1, pBT7, pSGS1, pSW2, pGRW11) and Haemoproteus (hPARUS1, hPHSIB1, hWW2) with the overall prevalence of 65 %. The Plasmodium infections predominated (prevalence of 49.5 %), whereas Haemoproteus infection rate was much lower (prevalence of 16.5 %). We showed significant differences in infection status between study years and age classes when all parasite lineages were analysed together or the two most common lineages were analysed separately. Overall, older birds showed higher prevalence. A significant interaction between year and genus effect significantly explained variation in infection intensity. This interaction stems from a significant yearly variation of the infection intensity with Plasmodium, while such an effect is not present for Haemoproteus infections. More importantly, the intensity of infection with Haemoproteus was significantly higher than with Plasmodium in 3 out of the 4 study years with data.

Effect of haemosporidian infections on host survival and recapture rate in the blue tit

“…This suggests that the effect of infection might be masked in a combined analysis. In contrast to the above studies, in which the majority of infections was caused by parasites from one genus: either Plasmodium or Haemoproteus, in our population the majority of infections is caused by two parasite species, from both genera: P. circumflexum and H. majoris (Podmokła et al 2014b). Because both of them are expected to negatively affect host survival prospects, we predict lower survival rates of infected individuals compared to uninfected ones and potentially different effects of infections with Plasmodium and Haemoproteus.…”

“…We investigated the potential effect of avian malaria infections, as well as individual age and sex, on the survival prospects in the blue tit. Our study population is exposed to infection with parasites from the Plasmodium and Haemoproteus genera, with the former genus being the dominant one (Podmokła et al ). Previous studies on blue tits in populations infected with only one parasite genus or sporadically also with the other genus have shown a negative effect of Haemoproteus parasites on host survival (Martinez‐de la Puente et al 2010) and a small effect of Plasmodium on survival (Lachish et al ).…”

“…We investigated the potential effect of avian malaria infections, as well as individual age and sex, on the survival prospects in the blue tit. Our study population is exposed to infection with parasites from the Plasmodium and Haemoproteus genera, with the former genus being the dominant one (Podmokła et al 2014b). Previous studies on blue tits in of the effect of Haemoproteus on recapture rates relative to both Plasmodium and uninfected included zero (Haemoproteus state relative to the uninfected state  0.7 (-0.18, 1.59) and Plasmodium relative to Haemoproteus  -0.38 (-0.59, 1.34)).…”

Sex-specific effects of parasites on telomere dynamics in a short-lived passerine—the blue tit

“…Intensity of infection (parasite DNA copy number) was then quantified via qPCR, comparing a focal sample with standard curves created using full-length cyt b PCR products from P. circumflexum and H. majoris (as described in (Knowles et al 2011). (For more details on primers, reaction setups, reagent concentrations and instruments, please see Podmokła et al (2014a, b)).…”

Haemoproteus infection status of collared flycatcher males changes within a breeding season

“…Cosgrove et al (2008) found that increase in vector abundance was followed by an increase in Plasmodium prevalence from spring to autumn within a blue tit Cyanistes caeruleus population, but prevalence was also positively correlated with the age of the host individuals. Others found changes in infection status within individual hosts even within the reproductive season (Knowles et al 2011) and also between years (Knowles et al 2011;Lachish et al 2011;Podmokla et al 2014). However, none of them tried to investigate the possible factors behind and the fitness consequences of changes in individual infection status.…”