keywords: Kokona, Karu, vector competence, Ochocerciasis
A vectorial study was conducted at Kokona and Karu Local Government Areas of Nasarawa State to assess the vector competence and transmission rates of onchocerciasis in the two local government areas. Monthly black fly catching was carried out over a period of 12 months, January to December 2010. A total number of 278 blackflies were caught for the period of study at the two Local Government areas. Kokona LGA recorded 207 blackflies while Karu LGA recorded 71 blackflies. Morphological identification of blackflies was as forest or savannah types. Dissections of blackflies were carried out to determine parous rate; infection and infectivity rates. The result indicated a seasonal (wet season) biting activity with a peak in month of September at both LGAs. The savannah species dominant the flies caught 94(49.7%) were parous flies for Kokona LGA while 19(30.2%) parous flies dissected for Karu LGA. At Kokona LGA 49(25.9%) were infected with Onchocerca volvulus L3 larvae, while Karu LGA recorded zero L3 larvae. The maximum monthly biting rate (MBR) and monthly transmission potential (MTP) for Kokona LGA recorded 502* in the month of September and 137.8B, respectively. The annual biting rate (ABR) and annual biting potential (ATP) for Kokona LGA was 1582 and 417, respectively; while Karu LGA recorded 210 Maximum monthly biting rate (MBR) in month of September and Minimum monthly biting rate was noted in the month of May 07.8. The monthly transmission potential (MTP) recorded Zero, while annual biting rate (ABR) of 542 and annual tansmission potential (ATP) of Zero was recorded for Karu LGA. L3/ 1000 parous flies for Kokona LGA and Karu LGA recorded 2923.6 and Zero respectively. The results were statistically analysed using analysis of variance (ANOVA) and separation of means to determine least significant difference (LSD). Transmission rates were significantly decreased in relation to study areas (p<0.05). The findings recorded low Onchocerciasis transmission in Kokona LGA and no transmission in Karu LGA in the year of study.
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