Acceptability of test and treat with doxycycline against Onchocerciasis in an area of persistent transmission in Massangam Health District, Cameroon.

The main onchocerciasis elimination strategy is annual Community-Directed Treatment with ivermectin (CDTi). However, as a response to persistent high infection prevalence in Massangam Health District in Cameroon, two rounds of alternative treatments including biannual CDTi, ground larviciding and test and treat with doxycycline (TTd) were implemented. This led to a significant prevalence reduction from 35.7% to 12.3% (p<0.001) as reported by Atekem and colleagues. Here we report on the acceptability of TTd component based on qualitative and quantitative data. The TTd involved microscopic examination for microfilaria in skin biopsy and those infected were offered doxycycline 100 mg daily for 35 days by community-directed distributors (CDDs). Participation level was significantly high with 54% of eligible population (age > 8, not pregnant, not breastfeeding, not severely ill,) participating in the test in each round, increasing to 83% over the two rounds. Factors associated with non-participation included mistrust, being female; being younger than 26 years; short stay in the community; and belonging to semi-nomadic sub population due to their remote and disperse settlement, discrimination, their non selection as CDD, and language and cultural barriers. Treatment coverage was high -71% in round 1 and 83% in round 2. People moving away between testing and treatment impacted treatment coverage. Some participants noted mismatch between symptoms and test result; and that ivermectin is better than doxycycline, while others favoured doxycycline. CDD worried about work burden with unmatching compensation. Overall, TTd participation was satisfactory. But can be improved through reinforcing sensitisation, reducing time between test and treatment; combining TTd and CDTi in one outing; augmenting CDDs compensation and/or weekly visit; exploring for frequently excluded populations and adapting strategies to reach them; and use of a sensitive less invasive test.

Evaluating the impact of alternative intervention strategies in accelerating onchocerciasis elimination in an area of persistent transmission in the West Region of Cameroon.

BACKGROUND: Alternative strategies are recommended to accelerate onchocerciasis elimination in problematic areas including areas where annual ivermectin (IVM) distributions are unable to interrupt transmission. The aim of this study was to accelerate progress towards elimination in the Massangam health district, West Region of Cameroon where impact evaluations demonstrated ongoing transmission of onchocerciasis infection and high microfilaria (mf) prevalence despite more than 20 years of annual IVM distribution. METHODOLOGY/PRINCIPAL FINDINGS: Parasitological, entomological, and breeding site surveys were conducted in 2015 delineating a focus of high transmission and identified three communities with high mf prevalence. Individuals in these communities were screened for mf yearly for a period of two years and those positive treated each year with doxycycline 100mg daily for five weeks. In addition, surrounding communities were given biannual IVM. Temephos-based applications were performed once a week for 10 consecutive weeks on Simulium damnosum s.l. breeding sites. Parasitological and entomological assessments were conducted after two years of implementation and findings compared with 2015 baseline. Alternative strategies accelerated progress towards elimination through a significant mf reduction (χ2: 40.1; p<0.001) from 35.7% (95%CI: 29.0-42.8) to 12.3% (95%CI, 9.0-16.4). Reductions were furthermore recorded over a longer period, with a reduction of prevalence of 29.0% under AIS in 2017-2019 compared to 14.6% with IVM in 2011-2015; and by 23.2% following the two years of alternative strategies compared to 20.3% reduction over 15 years of treatment with IVM (1996-2011). Entomological assessment demonstrates that transmission is still ongoing despite the reduction in mf which is expected in an environment with complex breeding sites and open transmission zones, i.e., where migration of flies or humans to and from neighbouring areas is common. CONCLUSION/SIGNIFICANCE: This study provides evidence that alternative strategies are feasible and effective and should be considered in areas where transmission is sustained throughout long term uninterrupted MDA with IVM. However, there is need to consider wider transmission zones, and further explore optimal timing of larviciding with treatment to impact transmission.

A cross-sectional study of Simulium damnosum sensu lato breeding sites and species distribution in Sudan savanna, mixed savanna-forest and rainforest regions in Cameroon.

BACKGROUND: The presence of breeding sites and distribution of species of Simulium damnosum sensu lato are critical in understanding the epidemiology of onchocerciasis and evaluating the impact of elimination interventions. Reports on breeding sites and species distribution of members of S. damnosum s.l. in Cameroon are scarce and the few ones available date back to more than three decades. The aim of this study is to provide information on S. damnosum breeding sites across the rainy (RS) and dry (DS) seasons and the species composition in three different regions in Cameroon: Southwest (SW), Northwest (NW) and North (N). METHODS: A cross-sectional two-season study was carried out in three regions with different ecological characteristics (SW-rainforest; NW-mixed forest-Guinea savanna; N-Sudan savanna). Pre-control onchocerciasis endemicity, relief maps and historical entomological information were used to identify potential rivers for purposive sampling. Sampled larvae were fixed in Carnoy's solution and sorted, and S. damnosum s.l. larvae were stored until identification by cytotaxonomy. Geographical coordinates of potential breeding sites were recorded to produce maps using ArcGIS, while Chi-square tests in SPSS were used to test for any differences between black fly seasonal breeding rates. RESULTS: A total of 237 potential breeding sites were sampled (RS = 81; DS = 156) and 72 were found positive for S. damnosum s.l. The SW had the most positive sites [67 (RS = 24; DS = 43)], with a significant difference in the rate of breeding between the seasons (P < 0.05). Among 68 sites visited in both seasons, 16 (23.5%) were positive in one of the two seasons with more sites positive in DS(11) than RS(05), 14 (20.6%) and 38 (55.9%) respectively positive and negative in both seasons. Simulium damnosum sensu stricto and S. sirbanum were the main species in the N, while S. squamosum and S. mengense were the predominant species in the NW and SW. Simulium soubrense and S. yahense were uniquely recorded in the SW. CONCLUSIONS: A comprehensive mapping of breeding sites requires rainy and dry seasons sampling. This study demonstrates that a breeding site survey of S. damnosum s.l. is achievable in forest as well as savanna zones. Not all potential breeding sites are actual breeding sites. Observation of S. soubrense in the SW indicates changes in species composition over time and could affect onchocerciasis epidemiology in this area.