Genetic Analysis of Tritrophic Interactions between Entompathogenic Nematodes, Symbiotic Bacteria and Blood – Sucking Flies.

Abstract

Mosquitoes are responsible for millions of deaths a year through the viruses and parasites they vector. Many of these vector species have successfully expanded their range into temperate climates due to a combination of climate change and the easy movement of goods and people around the world. The temperate climate of the U.K. is home to 34 native species, several of which bite humans and are capable of vectoring pathogens more commonly associated with warmer climates, therefore the threat of mosquito-borne illness in the U.K. is a very real possibility. Many vector mosquito species have evolved resistance to traditional chemical insecticides and the search for novel control strategies in endemic areas is a priority in vector control. Entomopathogenic nematodes (EPNs) are microscopic roundworms, which are obligate parasites of insects from the family Rhabditae. In particular, soil-dwelling nematodes from the genera Heterorhabditis and Steinernema. Presently EPNs are used in a range of plant-based industries as a chemical-pest control. However, previous laboratory research has shown that EPNs are capable of killing more than 250 species of insect including a selection of vector species and nuisance arthropods. This thesis is concerned with discovering whether commercially available and naturally occurring strains of EPNs from the U.K. could be used as an effective biocontrol agent for mosquito and chironomid species. This study includes a snapshot of the current EPN diversity in the U.K. which found four different Steinernema species, including the first molecular confirmation of Steinernema carpocapsae. EPNs from both field-collected and commercial sources were capable of killing and parasitizing two native and tropical mosquito species and Chironomus plumosus. Commercial strains were more effective at killing both, however, the native field-collected, mosquito species Ochlerotatus detritus was susceptible to field-caught EPNs, unlike the tropical, lab-reared Aedes aegypti. EPNs were found to be capable of tolerating the extremes of habitat that mosquito species can inhabit in laboratory tests. These studies have shown that with further research including viable field trials that EPNs could be very useful to add to a range of vector and nuisance control measures when used appropriately.