Factors Affecting Oviposition and Larval Development of Anopheles arabiensis in East Nile Locality - Khartoum State.

Longitudinal study for larval survey was carried out in the period between March 2009 and August 2009 in East Nile unit area in Khartoum. The study showed that Anopheles arabiensis larval presence varied significantly between different types of breeding sites. Although the larvae were collected from all identified types of water accumulations, the most important breeding sites were The Nile flood pools 36%, rain pools 22.6%; broken drinking water pipes leakages 20%, irrigation channels seepage 15.3% and brick making sites 12.5%. The study showed that the presence of Anopheles arabiensis larvae was influenced by physical, chemical and biological characteristics of the breeding sites. Habitats with warm water, Anopheles arabiensis larvae were found in water with a range of surface temperature between 16 and 42 °C. The percentages of positive breeding sites increased with in crease in temperature. The percentage of positive breeding sites with water salinity of 0 g/l was 4.3%, and those with salinity ranging between 0.1and 0.5 g/l was12.1% and those with a salinity of more than 0.5 g/l was 3.2%. The percentage of positive breeding sites with a pH of 3-6 was 6.9%, and a pH of 6.5-7.5 was 7.8% and a pH of 8-9 was 23.9 %. The percentage of positive breeding sites within water surface areas of less than one sq meter was 4.2% and in a surface range of 1-10 sq meters was 14.5% and in more than 10 sq meters was 7.4%. In a water depth of less than 10 cm, the percentage of positive breeding sites was 8.9%, and a range of water depth of 10-50 cm was 12% and in a depth of more than 50 cm, the percentage was 3%. Sunlight affected the number of Anopheles arabiensis breeding sites. The percentage of positive breeding sites in water with less than 25% shade was 9.9%, and a range of shade of 25-75% was 6.8%and in a shade of more than 75% was 1.3%. The presence of surface algae affected the breeding sites. The percentage of breeding with surface algae was 23% and those without surface algae were 4.9%. The percentage of positive breeding sites detected in water with aquatic vegetation was 7.9%, while those in water without aquatic vegetation was 5.2%. The presence of other species of mosquitoes affected the percentage of positive breeding sites of Anopheles arabiensis. Thus in water with other mosquito species the percentage of positive breeding sites was 47.2 % and those without other mosquito species were 3.5%. The presence of other groups of aquatic invertebrates affects the percentage of positive breeding sites of Anopheles arabiensis. In waters with other aquatic invertebrates the percentageof positive breeding sites was 32.3% and those without other aquatic invertebrates the percentage of positive breeding sites was 0.9%. Anopheles arabiensis larvae were not affected with amount of organic content and were also not affectedwith the degree of turbidity of water. The presence of Anopheles arabiensis in East Nile Unit depended mainly on The Nile River level and the rainy season. The highest percentage of positive breeding sites was found during the post-flood season (36 %) and rainy season (22.6). Larval surveys provided spatial and temporal information about Anopheles arabiensis breeding sites which is strongly required for larval control. The study recommended that more comprehensive studies should be carried out over a longer period of time to determine the effect of the natural variations in the breeding sites on Anopheles arabiensis larvae presence and density