MOSQUITO SPECIES COMPOSITION, ABUNDANCE AND PHYSICOCHEMICAL FACTORS OF RICE FIELDS IN MINNA, NIGER STATE, NIGERIA

Abstract

The mosquito species diversity and fitness of rice fields in Minna, Niger State Nigeria were studied. Four selected Rice fields located in Fadikpe, Bosso, Maitumbi and Chanchaga areas of Minna, were investigated for the Ecology of Rice field Mosquitoes, as a pre-requisite for developing effective control measures. Mosquito Larvae and Water samples were concurrently collected in the sampled Habitats between August and October 2012, while Soil samples were collected in November same year. Immature mosquitoes recovered were reared to adults and identified in the Laboratory using Standard Morphological keys. Ten Mosquito species were encountered in the following order of decreasing abundance: Culex pipiens pipiens 651(21.9%)> Culex quinquefasciatus 421(14.2%)> Anopheles gambiae 400 (13.5%)> Anopheles funestus 334 (11.2%)> Culex restuans 297 (10.0%)> Anopheles maculipalpis 187(6.3%)> Anopheles quardrimaculatus 178(6.0%)> Aedes dorsalis 173 (5.8%)> Aedes aegypti 169 (5.7%)> Aedes vexans 162 (5.5%), with species density significantly higher in rainy season than dry season. The results of water quality analyses indicated different degrees of variations in physicochemical parameters of the Rice fields in different locations. Statistically, Temperature, pH, Turbidity, Alkalinity, Hardness, Phosphate, Ammonia, Carbon dioxide, Chloride, Dissolved Oxygen and Biochemical Oxygen Demand were not significantly different (P>0.05) among Rice fields. However, Conductivity, Sodium, Potassium, Nitrate varied significantly (P<0.05). The results of dry season Soil analyses revealed the following mean values of physicochemical parameters as follows; Nitrogen=0.14%, Phosphorus=5.6mg/kg, Sodium=600mg/kg, Potassium=442.5mg/kg, Conductivity=224µS/cm, pH=7.61, Organic matter=1.59%, Sand=62.1%, Clay=30.1% Silt=7.8%. Statistically, the soil physicochemical parameters varied significantly (P<0.05) among Rice fields. The fluctuating asymmetry of Rice field mosquitoes revealed a high vectorial fitness. Significant Correlations between Mosquito abundance and physicochemical parameters of breeding Habitats were recorded for all species in both rainy and dry seasons. The Mosquito species encountered in this study are of Public Health importance, and the findings of the study should guide implementation of adequate vector control in Rice fields.