Evidence for carry-over effects of predator exposure on pathogen transmission potential

Abstract

Accumulating evidence indicates that species interactions such as competition and predation can indirectly alter interactions with other community members, including parasites. For example, presence of predators can induce behavioural defences in the prey, resulting in a change in susceptibility to parasites. Such predator-induced phenotypic changes may be especially pervasive in prey with discrete larval and adult stages, for which exposure to predators during larval development can have strong carry-over effects on adult phenotypes. To the best of our knowledge, no study to date has examined possible carry-over effects of predator exposure on pathogen transmission. We addressed this question using a natural food web consisting of the human malaria parasite Plasmodium falciparum, the mosquito vector Anopheles coluzzii and a backswimmer, an aquatic predator of mosquito larvae. Although predator exposure did not significantly alter mosquito susceptibility to P. falciparum, it incurred strong fitness costs on other key mosquito life-history traits, including larval development, adult size, fecundity and longevity. Using an epidemiological model, we show that larval predator exposure should overall significantly decrease malaria transmission. These results highlight the importance of taking into account the effect of environmental stressors on disease ecology and epidemiology.

Larval nutritional stress affects vector life history traits and human malaria transmission

“…Nutrition is one such environmental factor that can also impact host-pathogen interactions by affecting both partners. This is of great importance in vector-borne diseases as any alterations in individual life history traits could have crucial implications for transmission through changes in key parameters of vectorial capacity1214152122233132. Using a sympatric An .…”

“…their ability to develop and transmit pathogens789101112) which are all factors influencing vectorial capacity (i.e. the potential intensity of transmission by mosquitoes, see details in ref.…”

Keystone nonconsumptive effects within a diverse predator community

“…The larvae use energetically costly "diving" behaviors to escape from aquatic predators (Futami, Sonye, Akweywa, Kaneko, & Minakawa, 2008). Deployment of predator defenses as larvae can reduce adult mosquito longevity (Costanzo, Muturi, & Alto, 2011;Roux et al, 2015) and suppress mosquito immune function (Op de Beeck, Janssens, & Stoks, 2016), which might be expected to limit or increase, respectively, mosquito vectorial capacity (Kambris et al, 2010;VanderWaal & Ezenwa, 2016). However, this work exposed larvae to a single predator species, so it remains unclear how NCEs scale with more realistic levels of predator diversity that occur in natural habitats (e.g., Medlock & Snow, 2008).…”

Effect of irradiation on the survival and susceptibility of femaleAnopheles arabiensisto natural isolates ofPlasmodium falciparum

“…Unlike the first assay in which mosquitoes were maintained on a 5 % glucose solution ad libitum, mosquitoes received a 2.5 % glucose solution every other day in this second assay. This was supposed to induce nutritional stress in mosquitoes and help to better detect possible effects of radiation on survival (Roux et al ., 2015; Poda et al ., 2018). Inconsistent effects of irradiation on the survival of mosquito females were previously observed, with some studies reporting either lifespan reduction (Terzian, 1953; Brelsfoard, St Clair and Dobson, 2009), no effect (Darrow, 1968; Wakid et al ., 1976; Brelsfoard, St Clair and Dobson, 2009; Dandalo et al ., 2017) or even increase (Brelsfoard, St Clair and Dobson, 2009).…”