Host selection and feeding preferences of farm-associated mosquitoes (Diptera: Culicidae) in the United Kingdom

Abstract

Livestock farms sit at the interface between humans, livestock species and wildlife. However, limited data exist on mosquito-vertebrate host interactions on farms in the United Kingdom. This thesis therefore aimed to understand mosquito-vertebrate host interactions on UK livestock farms using a combination of field collections, colony mosquito experiments and molecular techniques for species identification and blood meal analysis. Field collections conducted between 2012 and 2014 yielded a total of 22 693 adult mosquitoes comprising 7 genera and 18 species. Fifteen species displayed human biting activity as assessed by human landing catch, with a maximum observed biting pressure at a single farm of up to 89 bites per 25 minutes at sunset. The avian biting rate, as assessed by the use of chicken-baited traps, was considerably lower than the human biting rate, but demonstrated the ornithophilic activity of three mosquito species, two of which had not previously been collected by such an approach in the UK. Field-caught blood-fed mosquitoes were subjected to a three-stage, targeted analysis, demonstrating that a single DNA extract from an engorged mosquito abdomen provides sufficient DNA for species delineation of Anopheles maculipennis s.l., blood meal identification and detection of myxoma virus. This study implicated Anopheles atroparvus, for the first time, in the transmission of myxomatosis between wild rabbits. The blood meals of over 900 mosquitoes of nine species were identified, revealing feeding on 5 mammalian and 14 avian hosts. Importantly, this study identified key potential vector species Culex pipiens f. pipiens as feeding on both resident and migratory birds. Collectively, these results demonstrate that UK livestock farms support ornithophagic, mammalophagic and anthropophagic mosquito populations which, at certain farms, can lead to a severe nuisance biting pressure on humans. The described feeding of potential vector species, such as newly-established Culex modestus, on farm-associated domestic and wild hosts, suggests that certain mosquito species could play a role in facilitating future pathogen transmission cycles on livestock farms in the case of a novel incursion.