What determines mosquito communities? understanding the ecology of infectious disease Maarten Schrama, Erin Gorsich, Bree Beechler and many others 14-03-2017 Most infectious diseases are vector-borne For many people on this planet, vector-borne diseases are an important link with the ecosystems around them Johnson et al., 2015, Science Mosquitoes most important vectors for a wide variety of diseases Malaria Anopheles arabiensis Zika Chickungunya Rift Valley Fever Wesselsbron Middelburg Dengue Aedes (albopictus/aegypti) Viral pathogen West Nile Virus Sindbis Culex (univittatus) Modern disease suppression Widespread pesticide resistance • Important side effect: predators are also killed, and recover much slower than mosquito populations (Service, 1977!) Service 1977, Mortalities of the Immature Stages of Species B of the Anopheles Gambiae Complex in Kenya: Comparison Between Rice Fields and Temporary Pools, Identification of Predators, and Effects of Insecticidal Spraying. J. Med. Ent. Another major problem: Most (human) infectious diseases originate from animals Ebola West Nile Fever Culex quinquefasciatus Predicting disease outbreaks? + Beck-Johnson et al 2012, PloSOne Pesticide remains? Presence of hosts? BIG QUESTION Which ecosystem properties make an area conducive of producing vector-borne diseases? Water quality? Aquatic biodiversity? Study Area: Kruger NP 1. MAP OF KRUGER Rural area (outside the park) Natural area Eutrophication Pesticides Atrazine Acaricides * * Mosquito communities depend on environmental conditions Water Treatment Plant, Skukuza Research Camp Shingwedzi (A) Human impacted site Anopheles spp. Culex antennatus (B) Natural site Culex naevei Culex quinquefasciatus Culex univittatus Culex poicilipes n=24 n=266 Culex argenteopunctatus Culex theileri Culex perfuscus Culex annulioris_type Mansonia africana Mansonia uniformis Can we predict mosquito community composition? • Which variables are most predictive? Inside -Landscape variables (vegetation parameters , soil moisture etc) Outside -Water quality parameters? (nutrient status, pesticides?) - Mosquito predators? (Dragonfly larvae/Backswimmers?) 13 Field Campaign 2017 Site: Phalaborwa Outside Kruger (rural area) Inside Kruger -50 m apart Temporary water body -min 10m from pond -Rotate every night CDC light trap Gravid Culex trap Gravid Aedes trap Tent trap Take Home message Research Partners Funders Experiments effects of experimental eutrophication Eutrophication leads to lower larval mortality Mortality Culex pipiens at different temps With Nutrients 100 No Nutrients 80 60 Mortality Mortality (%) 40 20 0 (or: % larvae not emerged (or: 13days aftercount) emerged not % larval larvae 16 18 20 22 24 26 28 30 32 Temperature (C) Schrama et al, in prep “Prior to our dependence on insecticides for vector population control, an emphasis was placed on ecological studies of vectors as well as their parasites and predators for biological control. Wetlands and water management for mosquito control and malaria prevention depended on knowledge of habitat specificity for egg laying and larval development (Herms and Gray, 1944).” Ecology of mosquitoes known? Rejmankova et al 2013: Chase & Knight 2003, Ecol Let. “Much of what we know about the detailed behavior of “because larval mosquitoes are components of a much individual insect vectors resulted from larger metacommunity of interacting species, the observations made during the pre-DDT era of the 1920’s interplay between biotic interactions (competitors and and 1930’s” predators) and abiotic constraints (temperature, habitat drying) is essential for understanding the controls About the following campaign (GLEM), which relied on mosquito abundance. By placing mosquitoes into a heavily on the use of pesticides, it was said: broader community context, a much better predictive framework can be developed for understanding and “it exterminated more medical entomologists than predicting year-to-year variation in mosquito mosquitoes” abundances” .