Malaria-induced changes in host odors enhance mosquito attraction

Abstract

Vector-borne pathogens may alter traits of their primary hosts in ways that influence the frequency and nature of interactions between hosts and vectors. Previous work has reported enhanced mosquito attraction to host organisms infected with malaria parasites but did not address the mechanisms underlying such effects. Here we document malaria-induced changes in the odor profiles of infected mice (relative to healthy individuals) over the course of infection, as well as effects on the attractiveness of infected hosts to mosquito vectors. We observed enhanced mosquito attraction to infected mice during a key period after the subsidence of acute malaria symptoms, but during which mice remained highly infectious. This attraction corresponded to an overall elevation in the volatile emissions of infected mice observed during this period. Furthermore, data analyses-using discriminant analysis of principal components and random forest approachesrevealed clear differences in the composition of the volatile blends of infected and healthy individuals. Experimental manipulation of individual compounds that exhibited altered emission levels during the period when differential vector attraction was observed also elicited enhanced mosquito attraction, indicating that compounds being influenced by malaria infection status also mediate vector host-seeking behavior. These findings provide important insights into the cues that mediate vector attraction to hosts infected with transmissible stages of malaria parasites, as well as documenting characteristic changes in the odors of infected individuals that may have potential value as diagnostic biomarkers of infection.

Host stress hormones alter vector feeding preferences, success, and productivity

“…For example, the American Robin (Turdus migratorius) in some regions of North America and the common blackbird (T. merula) in a region of Italy are bitten more frequently than expected from their relative abundance [34,35]. Mechanistic investigations of why these hosts are preferred over others would be particularly useful in the light of our findings, especially in locations where vector-borne diseases are emerging and hosts are naive [39]. In general, understanding the ramifications of individual host stress biology for community disease risk is important, as host organisms are forced to endure or exploit increasingly modified areas [60].…”

Heterogeneity in pathogen transmission: mechanisms and methodology

“…significantly more likely to acquire a pathogen than the general population) as well as superspreaders. For malaria, there is also evidence that hosts who are already infected with Plasmodium parasites become more attractive to mosquitoes (Lacroix et al 2005;Cornet et al 2013;de Moreas et al 2014). In mice, elevated volatile emission during infection with P. chabaudii has been linked to enhanced host attractiveness to A. stephensi mosquitoes (de Moreas et al 2014).…”

Host Manipulation by Parasites: Cases, Patterns, and Remaining Doubts

“…Vector-borne disease agents can increase the frequency or duration of the contacts between vectors and hosts, suppress vector reproductive investment (an effect that is likely to increase nutrient reserves in the vector that are available for the parasite), or increase vector longevity (Hurd, 2003). For example, mosquitoes (Anopheles gambiae) that carry the malaria parasite, Plasmodium falciparum, feed longer and are more prone to bite several people per night than P. falciparum-free mosquitoes (Koella et al, 1998;Smallegange et al, 2013), whereas malaria infection in humans, mice and birds, enhances their attractiveness to the mosquitoes (Lacroix et al, 2005;Cornet et al, 2013;De Moraes et al, 2014).…”