Entomological Evaluation by Dissection of Adult Simulium damnosum Complex for Larvae of Onchocerca volvulus , Following CDTI in Amagu Agba Community, Ishielu L.G.A-Ebonyi State, Nigeria

Abstract

The study was carried out to verify reports of persistent transmission of onchocerciasis, despite long-term Community Directed Treatment with Ivermectin, (CDTI). Blackflies were collected along Asu River using human baits. A total of 91 female Simulium damnosum complex adults were caught and dissected- using a dissecting microscope- for microfilariae of O. volvulus. 58 flies representing (63.70%) of the total number of captured flies were caught in the month of June while 33 (36.20%) were caught in July. Despite ivermectin treatment, evidence of O. volvulus transmission was documented in Amagu Agba. A total of 27 larvae were recovered from the three body segments of the dissected flies, of this number, 17 larvae were recovered from the head region and a total of 10 were recovered from the thorax and abdomen representing 62.96 % and 37.04 % respectively of the total number of larvae recovered. The proportion of infected flies recorded was 8 (8.8 %) while the proportion of infective flies recorded was 17 (18.7%) of the total number of infected and infective flies. The high proportion of infective flies is indicative of active transmission in and around the study area. This should not be so as CDTI is currently going on in the area. Some militating factors such as: patterns of treatment coverage and compliance, parasite ivermectin susceptibility, parasite immigration in flies or people, may be responsible for the current unsuccessful ivermectin treatment strategy.There is therefore need for consistent and effective ivermectin distribution pattern and its resultant onchocerciasis prevalence, detected with blackfly dissection techniques and or more reliably detected in both blackfly population and human subjects through a combination of some molecular-based detection techniques and biocontrol approaches. Adopting these measures together with community-ownership participation concept, will successfully interrupt transmission in Amagu Agba community and other endemic areas.