EFFECTS OF OIL SPILLS ON MOSQUITO ECOLOGY, PARASITE TRANSMISSION AND IMPACT ON UTOROGU COMMUNITY, DELTA STATE.

Abstract

The impact of oil spills on the water, soil and aquatic fauna, mosquito vectors and the socio-economic life of community dwellers in the Utorogu field of the Western Niger Delta was studied between 1998 and 2000. Soil and water samples were taken from pre-determined sites in the study area for physic-chemical analyses and soil and aquatic fauna assay. The socio-economic disposition of the community was studied using KAP questionnaire.

Results indicate that for both seasons of the year, the levels of major ions in the water bodies in the area were generally low (0 – 15 mg per litre). During the dry season, total ions were relatively higher than in the rainy season and the order of ionic dominance was mainly Na > K > Ca > Mg for cations and CO3 > CI > SO4 for the anoins. On the overall average, sodium and potassium accounted for nearly 60% of the total ions.

The most characteristic feature of the water bodies in the study area is their very dilute, very soft and acidic nature. The nature of the waters is most likely to limit their application and is expected to affect the populations of aquatic dwellers including mosquito larvae.

A total of 731 insects belonging to 7 orders were caught during the rainy season and 188 belonging to 5 orders during the dry season. This higher insect population during the rainy season (80%) as compared to the dry season (20%) was attributed to the absence of breeding sites in the dry season. During this study, Culex quinquefasciatus was the most abundant mosquito (71.5%) while Anopheles gambiae was the least abundant (1.5%). The average Monthly Biting Rates (MBR) for the mosquitos during the rainy season was 630 while that for the dry season was 48. The results obtained from experimental plots showed that apart from crude oil physically inhibiting oviposition of the females by trapping the limbs and soaking the wings, the insects did not oviposit in water with oil content greater than 5 ppm. The inhabitants of the communities have in general a negative perception of the impact of oil and gas activities in the area. The implications of the findings were discussed.