Abstract:
Currently, there are very few studies of avian malaria that investigate relationships among the host-vector-parasite triad concomitantly.
In the current study, we experimentally measured the vector competence of several Culex mosquitoes for a newly described
avian malaria parasite, Plasmodium homopolare. Song sparrow (Melospiza melodia) blood infected with a low P. homopolare
parasitemia was inoculated into a naïve domestic canary (Serinus canaria forma domestica).Within 5 to 10 days post infection
(dpi), the canary unexpectedly developed a simultaneous high parasitemic infection of Plasmodium cathemerium (Pcat6) and a low
parasitemic infection of P. homopolare, both of which were detected in blood smears. During this infection period, PCR detected
Pcat6, but not P. homopolare in the canary. Between 10 and 60 dpi, Pcat6 blood stages were no longer visible and PCR no longer
amplified Pcat6 parasite DNA from canary blood. However, P. homopolare blood stages remained visible, albeit still at very low
parasitemias, and PCR was able to amplify P. homopolare DNA. This pattern of mixed Pcat6 and P. homopolare infection was
repeated in three secondary infected canaries that were injected with blood from the first infected canary. Mosquitoes that blood-fed
on the secondary infected canaries developed infections with Pcat6 as well as another P. cathemerium lineage (Pcat8); none
developed PCR detectable P. homopolare infections. These observations suggest that the original P. homopolare-infected songbird
also had two un-detectable P. cathemerium lineages/strains. The vector and host infectivity trials in this study demonstrated that
current molecular assays may significantly underreport the extent of mixed avian malaria infections in vectors and hosts.
