A SURVEY OF OPEN LARVAL HABITATS OF MOSQUITOES.

CHAPTER ONE

INTRODUCTION

1.1            Background of the study

Mosquitoes are of great and remarkable importance to the health and economic development of man. They transmit and disseminate both human and animal diseases. Among the public health and veterinary important arthropods, mosquitoes rank first in the spread of such diseases as malaria, yellow fever, filariasis, dengue fever, encephalitis as well as other viral and bacterial diseases (Gillet, 1972; Service 1980). Apart from disease transmission, mosquitoes are regarded as public enemies because of their biting annoyance, noise nuisance, sleeplessness and allergic reactions due to their bites (Onyido et al., 2009a). According to World Malaria Report (WHO, 2010), malaria transmitted by female Anopheles mosquitoes still infects over 200 million people and kills up to 800,000 worldwide, with over 90% of the death still in subSaharan Africa. Malaria is quite endemic throughout Nigeria with more than 90% of the total population at risk of stable transmission (FMOH, 2010, Aribodor, 2009). At least 50% of the population suffers from at least one episode of malaria each year. An estimated 300,000 children die of malaria each year, and 11% of maternal mortality is related to malaria in pregnant women. The Federal Ministry of Health also notes that malaria leads to 25% of infant mortality and 30% of childhood mortality annually (FMOH, 2010). The disease also constitutes a major economic burden. About 132 billion Naira is lost to malaria annually in the form of treatment costs, prevention, and loss of work. This mosquito-borne disease is also responsible for the high rate of school absenteeism among students. These challenges are despite huge investments and efforts to control the disease over a century. Lymphatic filariasis transmitted by various species of mosquitoes including Anopheles, Mansonia, Culex and Aedes affects 120 million people with 40 million having overt disease and 80 million hidden damage (Ottesen, 2006). Yellow fever still remains one of the most debilitating diseases in tropical Africa and America. The disease which is endemic in most parts of Nigeria, is commonly noticed as devastating epidemics (it appears in cycles of epidemics) taking tolls on human lives and the economy (Monath, 1985; Tomori et al., 1991)Water supports many forms of life including the larval development of mosquitoes. Mosquitoes generally breed in various types of stagnant water. Mosquito larval stages develop in these various habitats and emerge to become adult mosquitoes that transmit diseases to man and his livestock. The adult mosquitoes show a very distinct preference for the types of water sources in which to lay their eggs. Each species has unique environmental requirements which could be determined from larval habitats (Okogun et al., 2003). According to The Urban Malaria Control Program of Dar es Salaam, Tanzania (TUMCP, 2005), mosquito habitat types can be broadly distinguished into Open Habitat and Closed Habitat. Open Habitats are defined as water bodies that are exposed to the open air and light. This means that in the Open Habitat, light can reach the water surface, and also plants can grow inside. These parameters have implications for mosquito breeding.

1.2     Statement of the problem

Part of the problem militating against effective and sustained control of mosquitoes and the diseases transmitted by them is that mosquitoes breed in diverse aquatic media that are naturally occurring and/or the creation of human activities. There are variations in the ecology of mosquitoes within and between countries of the world which is an integral part of the epidemiology of  mosquito borne diseases. It is generally  agreed that  a clear  understanding of the detailed ecology of mosquitoes is a pre-requisite for effective control of mosquito borne diseases. Tropical areas including Nigeria have the best combination of adequate rainfall, temperature and humidity, allowing for breeding and survival of different species of mosquitoes. Larval survey of mosquitoes can be used as an indicator of the risk of  mosquito borne diseases transmission in  a given area. This is because species specific preference for certain breeding sites has resulted in development of species sanitation programmes which usually achieved great success in different mosquito borne disease control in endemic parts of the world in early 20th century (Takken et al.,  1991;  Bradley,  1994).  The  application  of  larval  control  approach  is  considered  an  effective  method  of mosquito control and for the campaign to be successful, the type of habitat must be considered.    Subsequently, the most productive habitat should be given a priority attention. Larval surveys for mosquitoes are designed to assess the distribution of the aquatic stages of various disease transmitting mosquitoes of man and animals in a given community. A collection of baseline data on mosquito larval habitats over a period will inform vector control operations, thus improving public health. Such questions as what kind of mosquitoes should be targeted in control operation, when, where and how to target them, can satisfactorily be addressed after a detailed larval survey, thus in a bid to answer this questions was borne the focus of this study.

1.3     Objective of the study

This study therefore aims at investigating the open larval habitats of mosquitoes in Awka South Local Government Area (LGA) of Anambra State, Nigeria. The specific objectives include;

1.   To identify mosquito breeding habitats in the study area.

2.   To identify the species of mosquitoes breeding in these larval habitats in the three selected communities in the study area.

3.   To determine the preferred larval habitats for the species of mosquitoes.

4.   To determine the seasonal variation of mosquito larvae in the study area.

1.4     Research Hypothesis

HO: There is  no significant difference  in identified larval habitats and among species of mosquitoes in various larval habitats in the wet season

HI: There is  a significant difference  in identified larval habitats and among species of mosquitoes in various larval habitats in the wet season HO: There is no significant difference in larval distribution in wet and dry seasons.

HI: There is A significant difference in larval distribution in wet and dry seasons.

1.5     Significance of the study

Breeding sites of mosquitoes seem to persist in riverine communities. This is because of the presence of water required  for  egg  laying  in  the  lifecycle  of  mosquitoes  and  this  could  be  provided  all  seasons  in  riverine communities. The result of this study on Larva survey  will be relevant to inform vector control operations, researcher thus improving public health. More so, the study will contribute empirically to the body of existing knowledge as serve as reference material to student ans scholars who wishes to conduct further studies in related field.

1.6     Scope of the study

The scope of this study borders on a Survey Of Open Larval Habitats Of Mosquitoes. Although mosquitoes seems to persist in rural communities due to the presence of water required for egg laying,  It then means that different mosquito species are likely to be found there; which may pose serious risk of mosquito borne diseases. However, there is  no information on the  mosquito fauna  and mosquito borne diseases present in  some riverine areas  of South Eastern Nigerian. This is the reason why the study will be delimited to wka, Isiagu, Nibo and Umuawulu communities in Awka South Local Government Area of Anambra State.

1.7     Limitation of the study

In the course of conducting this research work it is expected that the following will constitute impediments to the effective conduct of the study such as Time constraint within which the study must be completed, Financial constraint, Inaccessible and inadequate data and also, combining project work with several other activities is another stressful task that may not allow me to cover research materials extensively. Nevertheless, it is   believed that the above limitations will in no way affect the reliability and validity of the research study.