Aedes mosquitoes in Hawaii

M.S. University of Hawaii at Manoa 2011.Includes bibliographical references.1.1. Introduction The presence in Hawaii of insect disease vectors presents risks to public health, economic well-being, and conservation of rare native species. Mosquito-borne dengue and avian malaria are just two important examples impacting Hawaii in the last century. While geographic isolation limits the arrival of alien species, the rarity of these immigration events also makes the islands uniquely vulnerable in several ways. Island ecosystems are susceptible to invasion (Elton 1958; Denslow 2003), and this includes invasion by vectors, pathogens and parasites (Riper III et al. 1986). Further, human populations in islands with low endemicity of disease tend to be immunologically naive (Cliff and Haggett 1984), and political support and institutional memory for epidemic disease prevention may be poor when the interval between epidemics is long (Slosek 1986; Chadee and Rahaman 2000). Mosquitoes are a family of flies (Diptera: Culicidae) in which the adult females generally feed on the blood of vertebrates. The blood feeding adaptation exposes mosquitoes to a wide variety of pathogens, and they often vector disease from one host to the next, both within and between species (Marquardt 2005). Although Hawaii has no native mosquitoes, six species of biting mosquitoes have been introduced. Two of these mosquitoes, Aedes aegypti, commonly known as the yellow fever mosquito, and Aedes albopictus, the Asian tiger mosquito, are efficient Flavivirus vectors and have been responsible for epidemics of dengue in Hawaii and elsewhere (Effler et al. 2005; Gubler 1989). Ae. aegypti's arrival over a century ago was followed a few years later by Ae. albopictus, and both species dispersed throughout the islands. Ae. aegypti disappeared from the two northernmost major high islands, Kauai and Oahu, near the end of World War II, and declined further with the Aedes aegypti Eradication Program (AaEP) in the 1960s. Although the general outline of these events is well known, a thorough understanding of the historic record of introduction, population growth and interaction between these mosquito species is important to understand how these disease vectors came to be where they are today. In particular, Ae. aegypti is more anthropophilic and accounts for higher levels of human disease transmission worldwide (Lambrechts et al. 2010): its displacement by Ae. albopictus has potential disease impacts. Hawaii is a model for examining the mechanisms behind this displacement. Here we analyze the historical records of mosquito introductions in order to understand the factors that have led to the current distribution of Hawaii's mosquitoes. These factors may include some or all of the following: changes in climatic conditions; changes in the landscape; changes in dispersal rates. Importantly, all of these factors might be influenced, intentionally or otherwise, by human activities such as mosquito control