Intro1.docx

Chapter 1 THE PROBLEM AND ITS SCOPE

Introduction

Dengue is a mosquito-borne viral disease that has rapidly spread in all regions. Dengue is widespread throughout the tropics, with local variations in risk influenced by rainfall, temperature and unplanned rapid urbanization. Dengue virus is transmitted by female mosquitoes mainly of the species Aedes aegypti and, to a lesser extent, Ae. albopictus. This mosquito also transmits chikungunya, yellow fever and Zika infection. According to the Provincial Health Office, deaths caused by suspected dengue cases in Bukidnon tripled in 2018 compared to the previous year. Suspected deadly mosquito bites killed six in 2017 but the figure increased to as high as 24 last year when the province recorded 6,935 suspected dengue cases. In 2017, the province only recorded 2,171 suspected cases. PHO data showed that Malaybalay City led in the number of deaths with five, followed by Valencia City with four. Moreover, highly-urbanized and populated areas contributed to a large number of dengue cases, led by the cities of Malaybalay and Valencia. The tribe Aedini (Family Culicidae) contains approximately one-quarter of the known species of mosquitoes, including vectors of deadly or debilitating disease agents. This tribe contains the genus Aedes, which is one of the three most familiar genera of mosquitoes. During the past decade, Aedini has been the focus of a series of extensive morphology-based phylogenetic studies published by Reinert, Harbach, and Kitching (RH&K). Those authors created 74 new, elevated or resurrected genera from what had been the single genus Aedes, almost tripling the number of genera in the entire family Culicidae. The Catalog of the Mosquitoes of the World, published in 1977 by Knight and Stone and its three supplements which were based on an earlier 1959 catalog, are the primary reference point for all modern mosquito systematics. These catalogs summarize the nomenclatorial organization of the entire Culicidae family and list all references that established those names. The family Culicidae includes 3,601 described species and subspecies- a number that steadily increases due to the intense medical and veterinary importance of mosquitoes. The family is organized into two subfamilies, the Anophelinae (482 species) and the Culicinae (3,119 species). Aedini, with 1,261 species, is the largest of the 11 tribes within Culicinae. The genus Aedes in the tribe Aedini is one of three best-known genera of mosquitoes (along with Culex and Anopheles) since many of its species are important vectors of certain diseases. ). Because of its medical importance, Aedes is recognized by thousands of researchers and operators concerned with mosquito control, public health, and veterinary health. Many mosquito species in the tribe Aedini, a cosmopolitan group represented by 11 genera and ≈1,239 species, are important vectors of human and animal diseases, and many others are of considerable economic importance as nuisance or pest species. To facilitate communication and

information exchange among epidemiologists, physicians, veterinarians, virologists, parasitologists, public health workers, and medical entomologists, it is essential that a stable nomenclature or system of names be maintained. Such communication has seldom been more important worldwide, because mosquito-borne diseases draw sincere attention from those charged with the responsibility of public health at all levels. Mosquito taxonomists strive to use new methods of analysis and new data sets to address the phylogeny and classification of mosquitoes, and future change in classification and nomenclature is inevitable. However, major changes in generic concept, the elevation of 32 subgenera within Aedes(sensu Edwards 1932, 1941) to generic status, and the resultant spelling changes in hundreds of species names by Reinert et al. (2004) demand consideration by all parties interested in mosquito-borne diseases. Mosquitoes, family Culicidae, comprise a monophyletic taxon (Wood & Borkent, 1989; Miller et al., 1997; Harbach & Kitching, 1998) belonging to order Diptera. The family is a large and abundant group that occurs throughout temperate and tropical regions of the world, and well beyond the Arctic Circle. Mosquitoes are most diverse and least known in tropical forest environments. Some 3,490 species are currently formally recognized (Harbach & Howard, 2007), but some 3–5 times this number may exist if the known species, like many Anopheles mosquitoes, prove to be isomorphic members of sibling species complexes. Mosquitoes are slender, long-legged insects that are easily recognized by their long proboscis and the presence of scales on most parts of the body. Larvae are distinguished from other aquatic insects by the absence of legs, the presence of a distinct head bearing mouth brushes and antennae, a bulbous thorax that is wider than the head and abdomen, posterior anal papillae and either a pair of respiratory openings (subfamily Anophelinae) or an elongate siphon (subfamily Culicinae) borne near the end of the abdomen. Mosquitoes are usually, and most reliably, identified as mature (fourth-instar) larvae and adults. Males are especially needed to distinguish many species because the females of various genericlevel taxa are remarkably similar in habitus. Whereas the taxonomy of numerous apparently closely related species is confounded by overt similarity, the limits of many supraspecific groups are clouded by morphological diversity. Some genera include diverse elements of indefinite affinities that will inevitably be recognized as separate monophyletic lines once they are thoroughly studied (Belkin, 1962; Judd, 1996; Harbach & Kitching, 1998; Reinert et al., 2004, 2006). The immature stages of mosquitoes occupy a spectrum of aquatic environments. They occur primarily in temporary or permanent bodies of ground water, but a large number of species occupy leaf axils, tree-holes, rock-holes, crab-holes, bamboo internodes, bromeliads and aroids, fruit shells and husks, fallen leaves and spathes, flower bracts, snail shells and pitcher plants. Some utilize artificial containers as well as the normal ground-water habitats. Mosquito-borne virus infections are on the raise, expanding its geographical range into new areas. The spread of infections from Africa and Asia to other continents is thought to be due to extensive travelling, trade, population growth in high-risk areas, globalization of vectors, urbanization, climatic change, as well as virus genome evolution. Female autonomous Aedes aegypti mosquitoes need a blood meal from a vertebrate host to reproduce. The nutrients taken up with the blood are used to synthesize large amounts of yolk proteins that are deposited in the eggs. Yolk delivers the energy and building blocks for embryogenesis. The need for blood in

order to reproduce makes anautogenous mosquitoes effective disease vectors because they require at least one insect host contact for every batch of eggs they develop. During feeding, adult female Aedes aegypti can take up more than their own body weight in blood (Yimer Muktar, Nateneal Tamerat and Abnet Shewafera). According to a study conducted in College of Veterinary Medicine, Haramaya University, the feeding habits of Aedes aegypti is more likely anthropophilic, endophagic and endophillic, which means they are biting mosquito, prefer to stay inside house and resting indoors after blood feeding while the meal is digested and the eggs mature, respectively. As a result, they can serve as vectors for numerous pathogens, e.g., arthropod-borne viruses or parasites, responsible for both human and animal diseases. The most important mosquito-borne viruses include flaviviruses such as Zika virus, Dengue virus (DENV), Yellow fever virus (YFV) and West Nile virus (WNV). Dengue puts stress on the local health system. Climate change has contributed to the spread of the Aedes aegypti and Aedes albopictus mosquitoes. The mosquitoes thrive when living near humans (in cities or suburbs) that offer ideal breeding sites like puddles, water tanks, containers and old tires. Lack of reliable sanitation and regular garbage collection also amplify the problem. We, the reseachers, strongly believe that massive public awareness not only to the measures on how to prevent mosquito-borne diseases but as well as disseminating facts on what mosquitoes are at the highest rate of spreading Dengue infection are salient actions for the society. Naming, describing and establishing the correct classification of mosquitoes is the first step to understanding their role in disease transmission. By naming and describing different species, we will gain a more complete picture of our mosquito fauna, and its role in disease transmission.