Mosquitoes are attracted by the odour of Plasmodium infected birds

Parasites can manipulate their hosts to increase their transmission success. Avian malaria parasites(Plasmodium) are thought to alter the cues such as host odour, used by host-seeking mosquitoes. Birdodour is affected by secretions from the uropygial gland and may play a role in modulating vector-host interactions. We tested the hypothesis that mosquitoes are more attracted to the uropygial secre-tions and/or whole-body odour (headspace) ofPlasmodium-infected house sparrows (Passer domesticus)than to those of uninfected birds. We tested the attraction of nulliparous (e.g. uninfected mosquitoeswithout previous access to blood) Culex pipiensfemales towards these stimuli in a dual-choice olfactome-ter. We used Gas Chromatography-Mass Spectrometry (GC–MS) analyses to assess whetherPlasmodiuminfection is associated with differences in the chemical composition of uropygial secretions. Mosquitoeswere more attracted to the odours of infected than uninfected birds, regardless of sex. However, the significant interaction between infection status and the stimuli (uropygial secretion or headspace) showedthat mosquitoes were more attracted to the headspace of infected birds; no differences were found in thecase of uropygial secretions. The compounds in the volatile lipophilic fraction of the uropygial secretiondid not differ between infected and uninfected birds. These results support the host manipulationhypothesis since avianPlasmodiumparasites may be capable of altering their host’s body odour, therebymaking infected individuals more attractive to mosquitoes.

This study was funded by projects CGL2015-65055-P and PGC2018-095704-B-100 from the Spanish Ministry of Science and Innovationand European Regional Development Fund (FEDER, Spain), and P11-RNM-7038 from the Junta de Andalucía (Spain). ADF was supported by a Severo-Ochoa grant from the Spanish Ministry of Economy and Competitiveness (SVP-2014-068571). LG was supportedby a Marie Sklodowska-Curie Fellowship from the European Commission (grant number 747729, ‘‘EcoEvoClim”).