Plastic responses of Plasmodium relictum to competent and non-competent mosquito bites

Environmental unpredictability challenges the transmission success of vector-borne parasites like Plasmodium, whose fitness depends on synchronizing the production of transmission forms, called gametocytes, with vector availability. Although mosquito bites are known to trigger Plasmodium responses, it remains unclear whether parasites respond specifically to competent vectors or adopt a generalist strategy. We experimentally infected birds with the avian malaria parasite Plasmodium relictum and exposed them to bites from either a competent (Culex quinquefasciatus) or a non-competent (Anopheles gambiae) vector species. Both exposures induced a rise in parasitaemia, but the response was significantly stronger to the non-competent species. Host inflammatory, humoral and stress markers remained similar across mosquito treatments, implying that unidentified physiological cues may underlie the parasite's response. No species-specific modulation of gametocyte conversion rate or sex ratio was observed. These findings suggest that P. relictum does not discriminate between mosquito species, instead employing a generalist, possibly bet-hedging strategy in response to any mosquito bite. Our results highlight the importance of mosquito community composition in shaping parasite transmission dynamics. If non-vector mosquitoes enhance Plasmodium transmission investment, shifts in vector assemblages due to climate change or control measures may have unanticipated effects on disease ecology.