We studied onchocerciasis transmission and impact on ocular morbidity in three health districts in North Region, Cameroon, where annual mass ivermectin treatment has been provided for 12–17 years. The studies, which took place from 2008 to 2010, consisted of skin snips for microfilariae (mf), palpation examinations for nodules, slit lamp examinations for mf in the eye, and Simulium vector dissections for larval infection rates. Adults had mf and nodule rates of 4.8% and 13.5%, respectively, and 5.5% had mf in the anterior chamber of the eye. Strong evidence of ongoing transmission was found in one health district, where despite 17 years of annual treatments, the annual transmission potential was 543 L3/person per year; additionally, children under 10 years of age had a 2.6% mf prevalence. Halting ivermectin treatments in North Cameroon now might risk recrudescence of transmission and ocular disease.

We followed up the 1996 baseline parasitological and entomological studies on onchocerciasis transmission in eleven health districts in West Region, Cameroon. Annual mass ivermectin treatment had been provided for 15 years. Follow-up assessments which took place in 2005, 2006, and 2011 consisted of skin snips for microfilariae (mf) and palpation examinations for nodules. Follow-up Simulium vector dissections for larval infection rates were done from 2011 to 2012. mf prevalence in adults dropped from 68.7% to 11.4%, and nodule prevalence dropped from 65.9% to 12.1%. The decrease of mf prevalence in children from 29.2% to 8.9% was evidence that transmission was still continuing. mf rates in the follow-up assessments among adults and in children levelled out after a sharp reduction from baseline levels. Only three health districts out of 11 were close to interruption of transmission. Evidence of continuing transmission was also observed in two out of three fly collection sites that had infective rates of 0.19% and 0.18% and ATP of 70 (Foumbot) and 300 (Massangam), respectively. Therefore, halting of annual mass treatment with ivermectin cannot be done after 15 years as it might escalate the risk of transmission recrudescence.

Summaryobjective Community-directed treatment with ivermectin (CDTI) for onchocerciasis control is targeted to meso and hyperendemic areas in Africa. Below the threshold, communities are considered hypoendemic and, mass treatment is not recommended. As policy begins to shift from control to elimination, the role of hypoendemic areas in maintaining Onchocerca volvulus needs to be re-examined. The study determined whether independent transmission occurs in a hypoendemic area in the North region of Cameroon.methods Ten 'high risk' communities along the River Mayo Douka system in Ngong Health District, at least 20 km from the nearest CDTI program were studied. Six hundred and forty-nine adults (over 20 years of age) and 561 children (under 10 years) were examined for nodules and microfilaria. A subsample of 334 adults was examined for onchocercal ocular morbidity. Simulium flies from 4 collection points were captured over 3 months annually for 2 years and dissected for larval stages of O. volvulus.results Nodule and microfilariae (mf) prevalence among adults was 12.20% and 2.91%, and 9.2% and 0.48% among children, respectively. Blindness because of onchocerciasis was insignificant, although low rates of chronic onchocercal ocular disease (<2%) were observed. conclusion Ngong is a 'hypoendemic' focus with likely low grade indigenous transmission in isolation from meso ⁄ hyperendemic areas. Consequently, transmission from hypoendemic areas could contribute to rapid disease recrudescence in the post-treatment phase of adjacent former meso and hyperendemic areas.

BackgroundTo estimate the prevalence of trachoma in the North Region of Cameroon in order to facilitate the planning of trachoma control activities in this region, a survey was carried out in 2011 and 2012 in 15 health districts (HDs).MethodologyA cross-sectional, two-stage cluster random sampling survey was carried out. The survey focused on two target populations: children aged 1 to 9 years for the prevalence of Trachomatous Inflammation-Follicular (TF) and those aged 15 and over for the prevalence of Trachomatous Trichiasis (TT). The sample frame was an exhaustive list of villages and neighborhoods of HDs. The World Health Organization simplified trachoma grading system was used for the recognition and registration of cases of trachoma.Principal Findings30,562 children aged 1 to 9 years and 24,864 people aged 15 and above were examined. In children aged 1–9 years, the overall prevalence of TF was 4.2% (95% confidence intervals (CI): 4.0–4.5%). Three (3) of 15 HDs in the region showed TF prevalence of ≥10% (Poli, Rey Bouba, and Tcholliré). The overall TT prevalence was 0.25% (95% CI: 0.20–0.33%). There were estimated 1265 TT cases in the region. The prevalence of blindness was 0.01% (95% CI: 0.00–0.03%), low vision was 0.11% (95% CI: 0.07–0.17%), and corneal opacity was 0.22% (95% CI: 0.17–0.29%).Conclusions/SignificanceThis survey provides baseline data for the planning of activities to control trachoma in the region. The overall prevalence of TF in the region is 4.2%, and that of TT is 0.2%; three HDs have a TF prevalence ≥10%. These three HDs are eligible for mass drug administration with azythromycin, along with the implementation of the “F” and “E” components of the SAFE strategy.