ABSTRACT

A survey of the mosquito fauna of Asaba, the Delta State capital of Southwestern Nigeria was undertaken between January and March 2009. The mosquito breeding sites, distribution, abundance and the influence of ecological factors on the mosquito population were determined. Asaba metropolis was subdivided into five zones based on population and human activities. Ovitraps were used to sample the Aedes mosquito populations. Larvae were collected once weekly using ladles, bowls, sieves and specimen bottles. Ecological sites studied were drains ground pools, discard vehicle tyres, domestic containers, tree holes and leaf axils. A total of 7,337 mosquitoes comprised of two mosquito genera (Aedes and culex) and three mosquito species, Aedes aegypti, Aedes albopictus and culex quinquetasciatus were collected, C. quinquefasciatus 6,431(87.7%) formed the bulk of the collection of the 7,337 larvae, drains yielded 6,202 (84.53%) of the collection. out of 960 ovitraps set, 291 (31.1%) were positive with aedes eggs that yielded 1,553 larvae from which 780 (72.4%) emerged as adults. Two aedes species A. aegypti 450 (57.7%) and A. albopictus 330 (42.3%) were collected from the ovitraps. Both larvae and eggs collected increased or decreased with increase in rainfall. The health implications of high breeding rates of mosquitoes in the drains and domestic water containers were discussed and recommendation for mosquito control, health education and maintenance of clean drains were made.

CHAPTER ONE

INTRODUCTION

Mosquitoes are widely distributed throughout the world and they utilize different water bodies for their breeding (WHO, 1982). Many species breed in both natural and arti cial containers, such as pools, gutters, coconut shells, tree holes, bamboo stumps, leaf axils, septic tanks and other similar water bodies (Ma ana, 1989; Aigbodion and Anyiwe, 2005). The distribution of mosquitoes is in uenced both directly and indirectly by climatic and environmental factors (Ma ana et al., 1998). Mosquitoes prefer an environment with certain resources such as food, shelter, breeding sites, favourable temperature and suitable humidity, in sufficient amount and at an appropriate time for development and survival (Romoser & Stoffolano, 1998). The recent increase in ecological and environmental modi cation due to agricultural activities and urbanization, has been observed to contribute to the breeding of various mosquito species in a rice and plaintation communities in Ogun State (Amusan et al., 2005).

Mosquitoes are unquestionably the most medically important arthropod vectors of disease. The maintenance and transmission of the pathogens that cause malaria, lymphatic filariasis, and numerous viral infections are mainly dependent on the availability of competent mosquito vectors (Monath 1985). Human malaria, caused

1

primarily by the protozoan species, Plasmodium falciparum and Plasmodium vivax, causes high mortality and morbidity in human and animal population across the world, leading to enormous economic loss (Soulsby 1982, Service 1980). The nematodes Wuchereria bancrofti and Brugia malayi are the principal etiologic agents of lymphatic filariasis, causing morbidity in over 100 million individuals ( Bockarie et al 1998). Hundreds of thousands of humans also are infected with mosquito-borne viruses, with yellow fever and dengue fever being two of the most important mosquito-transmitted viral diseases. Although the medical community has known for over a century the role mosquitoes play in the transmission of malaria and lymphatic filariasis, these diseases continue to have a devastating influence on the less privileged populations throughout the tropical and subtropical regions of the world (Service 1980). The current problems in controlling malaria are much more severe than those facing public health officials 30 years ago (Krogstad, 1996).The problems include resistance of vectors to insecticides and the Plasmodium parasites to drugs.

Studies to identify local mosquito species have been carried out in several parts of Nigeria including Ibadan, Lagos, Zaria, Benin, Enugu and Awka (Okorie, 1973; Ma ana, 1989; Anyanwu et al., 1999; Aigbodion & Odiachi, 2003; Onyido, et al 2002; Mbanugo, and Okpalononuju, 2003 (respectively). Constant studies on biology and larval ecology of mosquitoes have been observed as important tools in

2

mosquito control (WHO 1975). Such studies will help to determine the existing and disappearing mosquito species and their distribution (Ma ana et al., 1998; Anyanwu et al., 1999). The present study was designed to investigate the ovi-position and larval habitats of existing mosquito fauna in Asaba, Delta state capital of southwestern Nigeria and its possible public health implications. (on the residents). Specifically, it will Sample the mosquitoes using ovitrap and larval collection methods in part of Asaba metropolis in Delta State, so as to determine the Mosquito species composition, as well as distribution and relative abundance. ( of various Mosquito species in the area.)