Black Fly Diversity and Impacts on Human Welfare in Southeast Asia

Abstract

Black flies (Diptera: Simuliidae) are insects of medical and veterinary importance because some of them are vectors of human and livestock disease agents. Even without transmission of pathogens, black fly biting can affect human and animal welfare through nuisance and irritation. More than 2300 species of black flies have been recorded globally and about 20% of these occur in Southeast Asia (SE Asia). A total of 456 black fly species arranged in eight subgenera of the genus Simulium are found in this region. Although there is a long history (>100 years) of black fly study in some countries in SE Asia, extensive explorations began less than two decades ago. Recent advances in taxonomy using morphological, cytological, and molecular approaches have provided a backbone for other aspects of black fly study in this region. At least seven species are known as human-biters and two are considered pests in northern Thailand. Three black fly species (Simulium nodosum Puri, S. nigrogilvum Summers and S. asakoae Takaoka and Davies) in SE Asia have been found carrying animal-origin filarial parasites including two unidentified species of the genus Onchocerca that possibly cause human zoonotic onchocerciasis. At least two species (S. asakoae and S. chumpornense Takaoka and Kuvangkadilok) are possible vectors of avian parasites of the genus Leucocytozoon and Trypanosoma. However, further study is required to evaluate the impacts of black flies either directly (i.e. transmission of disease agents to humans) or indirectly (e.g. economic impact). In addition, it is highly likely that areas of high diversity await exploration in Laos, Cambodia, and some parts of Vietnam.KeywordsAquatic insectsBlack flyDiptera Onchocerca Vector