Identifying Drivers of Onchocerciasis Transmission in Ekiti State

This study sought to identify drivers of onchocerciasis transmission in the communities that failed  the 2024 onchocerciasis epidemiological assessment. Five key objectives were achieved; (i) profiling the demographic characteristics of community residents, (ii) evaluating the reach and coverage of ivermectin Mass Drug Administration (MDA) campaigns, (iii) identifying barriers to the MDA campaigns, (iv) investigating participants' exposure to black fly bites, and (v) assessing environmental factors supporting breeding of black flies in the study communities. 

 Profiling demography of community residents

Foremost, a total of 1741 community residents participated in this study (ranging between 275 to 316 across the communities). Most participants were females (57%), with mean age of 36 years, engaged in occupations such as trading (27%) and farming (25%), with 37% being migrants from other communities (55%), but majority have stable over the past 22 years (95%). Notably Iworoko had the highest number of migrant settlers (57%)  

 Reach of ivermectin-MDA campaigns

In 2022, only one of the seven communities was below target, while others reached above 75%. However, in 2023, the reach declined significantly across all communities except Araromi: Igbara Odo dropped from 88% to 6%, Asolo from 87% to 23%, Aisegba from 75% to 3%, Iworoko from 50% to 17%, and Ijesa-Isu from 77% to 59%. In 2024, the reach of medicines increased significantly in most communities except in Iworoko (41%).

Coverage of ivermectin-MDA campaigns

The survey coverage has been consistently sub-optimal since 2022, never exceeding 40% across the study communities. In 2022, coverage was below target in only 1 of the 7 communities (Iworoko at 47%), while others were above 75%. However, in 2023 and 2024, coverage declined significantly:- Igbara Odo: dropped from 85% to 5% in 2023, and rose to 36% in 2024.; - Asolo: dropped from 76% to 19%, and increased to 28% in 2024.; - Aisegba: dropped from 73% to 2%, and rose to 31% in 2024.; - Iworoko: dropped from 47% to 16%, and rose to 31% in 2024.; - Ijesa-Isu: dropped from 74% to 58%, and further to 33% in 2024.; - Araromi: dropped from 81% to 80% in 2023, and further to 38% in 2024.

Barriers to ivermectin-MDA campaigns

In 2022, only 24% of those recruited were not offered ivermectin, primarily due to refusals (29%), absenteeism (24%), and unawareness of the intervention (23%). By 2023, this number increased to 69%, with the main challenge being that the Community Drug Distributors (CDDs) never visited their households (70%). In Araromi, refusals (52%) and absenteeism (29%) were prevalent, while in Iworoko, it was primarily the absence of CDDs (46%) and refusals (20%). In 2024, 26% of the population was not offered ivermectin, with significant gaps in Aisegba (34%) and Iworoko (59%). The top reasons for poor reach in 2024 were refusals (30%), absence of CDDs (24%), and unawareness of the intervention (22%), with refusal being common across most communities except Igbara-Odo, absenteeism in Araromi (32%), and unawareness in Iworoko (30%).

 Community feedback on factors limiting effective coverage of Ivermectin-MDA campaigns

Community feedback from key informant interviews revealed several issues surrounding rumors of death with resulted in refusals, and poor timing of MAM among the populace who are always absent during the morning and afternoon hours

 Migratory behaviors as a risk factor to poor coverage or increased risk to blackfly bites

Only 31% of participants reported traveling frequently, with most from Aisegba (62%) and Iworoko (55%). The main reasons for travel were occupation (39%) and unplanned family/social duties (24%), with leisure travel being more common in Iworoko (40%). Overall, 37% of respondents indicated they had missed Mass Administration of Medicines (MAM) due to travel, particularly those from Iworoko (61%) and Ijesa-Isu (50%).

 Poor knowledge as a risk factor to increased risk to blackfly bites

Most participants (87%) were aware of onchocerciasis, with awareness levels ranging from 79% in Iworoko to 96% in Igbara-Odo. Approximately 75% identified blackflies as the vector, but this knowledge was notably poor in Aisegba (42%) and Iworoko (67%), where many attributed the disease to other unspecified causes. Additionally, 84% of participants had seen blackflies, and 62% correctly described their breeding sites as fast-flowing water bodies. However, knowledge about breeding sites was low in Aisegba (27%) and Iworoko (47%), with many respondents incorrectly believing blackflies breed in bushes or being unsure (68% in Aisegba, 53% in Iworoko). This lack of knowledge about the disease and vector breeding sites may reduce the likelihood of residents taking measures to protect themselves from blackfly bites.

Participants' exposure to black fly bites

Participants' exposure to blackfly bites varied, with 74% having seen blackflies perch on them. Most reported frequent bites while outside within the community (54%), outside at home (45%), or at work (24%). Intense biting within the community was particularly frequent in Asolo (93%), Iworoko (79%), and Igbara-Odo (67%). About 23% reported being bitten indoors, with indoor biting especially common in Ijesa-Isu. Daily bites were prevalent in Ijesa-Isu (79%), while weekly bites were more common in Igbara-Odo (67%) and Asolo (55%). Occasional bites were typical in Aisegba (78%) and Iworoko (55%). Children’s complaints about fly bites were intense at 47%, and more frequent  in Ijesa-Isu (93%) and Iworoko (51%). Most respondents experienced itching (95%) and swelling (1.9%) from the bites.

Environmental factors supporting breeding of black flies 

Human activities and environmental assessments confirmed the presence of fast-flowing rivers and vegetated surroundings in all the study communities, indicative of potential blackfly breeding sites. Spot-checks verified these conditions, where majority of those found at river sites complained about frequent bites, which is suggestive of  a potential breeding site requiring intervention.

Conclusion

This study highlights significant gaps in the reach and coverage of ivermectin MDA campaigns, influenced by refusals, absenteeism of community members during MDA, and poor dissemination of information the MAM program. The migratory behavior of the residents were majorly due to nature of job and other family or social duties, and this has influenced missing MAM, and could pose additional exposure to blackflies bite from other places. Exposure to fly bites is intense at 74%, and even among children below age 10 (at 47%). The poor knowledge about the cause and transmission in some of the communities may limit the ability of the residents to take informed decisions about protecting themselves from bites and swallowing ivermectin. Environmental factors supporting breeding of flies and high exposure to blackfly bites is thus a challenge. Addressing these issues through improved program fidelity, enhanced community engagement, and targeted interventions such as “slash and clear” at identified breeding sites is essential for better health outcomes.