On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: Better understanding transmission dynamics to inform changes in programmatic interventions.

BACKGROUND: Massangam health district (HD), in the West Region of Cameroon, has received ivermectin mass drug administration (MDA) for 20 years, however there is evidence of continued high transmission of Onchocerca volvulus. In order to better understand the transmission dynamics in the HD and inform intervention strategies there is a need to delineate the boundaries of the suspected area of high transmission within the wider transmission zone. METHODOLOGY/PRINCIPAL FINDINGS: Parasitological and entomological surveys were conducted to map out the breeding sites of Simulium damnosum and evaluate the prevalence of onchocerciasis in neighbouring communities, including Makouopsap sentinel community. Potential rapids were prospected for identification of S. damnosum larvae and black flies collected to determine infectivity rates. Adults were assessed for the presence of O. volvulus microfilariae through a skin snip biopsy and examined for the presence of nodules. Anti Ov-16 antibodies were tested for in children. Four perennial breeding sites were identified on the Rivers Mbam and Nja. Large number of flies were collected along the River Mbam, especially in the rainy season, with up to 955 flies per day, suggesting this river is a perennial source of black flies. A total of 0.8% of parous flies were infective across the study area. Parasitological studies provided evidence of high rates of infection in the sentinel community and three neighbouring communities, with 37.1% of adults microfilariae positive in Makouopsap. High Ov-16 seropositivity in children also provided evidence of recent on-going transmission. In comparison, communities sampled further away from the sentinel community and neighbouring breeding sites were much closer to reaching onchocerciasis elimination targets. CONCLUSIONS/SIGNIFICANCE: This study provides evidence of a particular geographic area of high transmission in an approximate 12 km range around the sentinel community of Makouopsap and the neighbouring breeding sites on the River Nja. To eliminate onchocerciasis by 2025, there is a need to explore alternative intervention strategies in this area of high transmission

Fifteen Years of Annual Mass Treatment of Onchocerciasis with Ivermectin Have Not Interrupted Transmission in the West Region of Cameroon

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

Risk factors associated with failing pre-transmission assessment surveys (pre-TAS) in lymphatic filariasis elimination programs: Results of a multi-country analysis.

Achieving elimination of lymphatic filariasis (LF) as a public health problem requires a minimum of five effective rounds of mass drug administration (MDA) and demonstrating low prevalence in subsequent assessments. The first assessments recommended by the World Health Organization (WHO) are sentinel and spot-check sites-referred to as pre-transmission assessment surveys (pre-TAS)-in each implementation unit after MDA. If pre-TAS shows that prevalence in each site has been lowered to less than 1% microfilaremia or less than 2% antigenemia, the implementation unit conducts a TAS to determine whether MDA can be stopped. Failure to pass pre-TAS means that further rounds of MDA are required. This study aims to understand factors influencing pre-TAS results using existing programmatic data from 554 implementation units, of which 74 (13%) failed, in 13 countries. Secondary data analysis was completed using existing data from Bangladesh, Benin, Burkina Faso, Cameroon, Ghana, Haiti, Indonesia, Mali, Nepal, Niger, Sierra Leone, Tanzania, and Uganda. Additional covariate data were obtained from spatial raster data sets. Bivariate analysis and multilinear regression were performed to establish potential relationships between variables and the pre-TAS result. Higher baseline prevalence and lower elevation were significant in the regression model. Variables statistically significantly associated with failure (p-value ≤0.05) in the bivariate analyses included baseline prevalence at or above 5% or 10%, use of Filariasis Test Strips (FTS), primary vector of Culex, treatment with diethylcarbamazine-albendazole, higher elevation, higher population density, higher enhanced vegetation index (EVI), higher annual rainfall, and 6 or more rounds of MDA. This paper reports for the first time factors associated with pre-TAS results from a multi-country analysis. This information can help countries more effectively forecast program activities, such as the potential need for more rounds of MDA, and prioritize resources to ensure adequate coverage of all persons in areas at highest risk of failing pre-TAS

Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon

Background The control of lymphatic filariasis (LF) caused by Wuchereria bancrofti in the Central African Region has been hampered by the presence of Loa loa due to severe adverse events that arise in the treatment with ivermectin. The immunochromatographic test (ICT) cards used for mapping LF demonstrated cross-reactivity with L. loa and posed the problem of delineating the LF map. To verify LF endemicity in forest areas of Cameroon where mass drug administration (MDA) has not been ongoing, we used the recently developed strategy that combined serology, microscopy and molecular techniques. Methods This study was carried out in 124 communities in 31 health districts (HDs) where L. loa is present. At least 125 persons per site were screened. Diurnal blood samples were investigated for circulating filarial antigen (CFA) by FTS and for L. loa microfilariae (mf) using TBF. FTS positive individuals were further subjected to night blood collection for detecting W. bancrofti. qPCR was used to detect DNA of the parasites. Results Overall, 14,446 individuals took part in this study, 233 participants tested positive with FTS in 29 HDs, with positivity rates ranging from 0.0% to 8.2%. No W. bancrofti mf was found in the night blood of any individuals but L. loa mf were found in both day and night blood of participants who were FTS positive. Also, qPCR revealed that no W. bancrofti but L.loa DNA was found with dry bloodspot. Positive FTS results were strongly associated with high L. loa mf load. Similarly, a strong positive association was observed between FTS positivity and L loa prevalence. Conclusions Using a combination of parasitological and molecular tools, we were unable to find evidence of W. bancrofti presence in the 31 HDs, but L. loa instead. Therefore, LF is not endemic and LF MDA is not required in these districts

Ivermectin and doxycycline treatments against Onchocerciasis: Adaptations and impact among semi-nomadic population in Massangam Health District, Cameroon.

We trialed strategies to reach semi-nomadic population with interventions targeting onchocerciasis including a combination of community knowledge and Geographical Information System (GIS) technology; nomad-specific sensitization; and mobile outreach. The interventions included ivermectin (ivm) mass drug administration (MDA) and treating infected individuals (found upon skin snip microscopy test) with doxycycline for 35 days. Microscopy-negative snips were further tested by Polymerase Chain Reaction (PCR). After 8 months, individuals immigrating or emigrating constituted 47% of the initial population; 59% of individuals not born in the area have immigrated during the last five years; 28% (age>9) reportedly never taken ivm; 72% (compared to 51% previously) of eligible population (age ≥ 5 years) took ivm; and 47% (age > 8, not pregnant, not breastfeeding, not severely ill,) participated in the test. A high prevalence of onchocerciasis,15.1%, was found upon microscopy & PCR test; 9/10 tested by skin snip microscopy and PCR at follow-up were all negative. Microfilaria prevalence and intensity upon skin snip microscopy reduced significantly from baseline following the intervention (8.9% to 4.1%, p = 0.032; 0.18 to 0.16, p = 0.013, respectively). The strategies considerably increased reach to nomadic camps. Treating with doxycycline in combination with ivm is feasible and has led to a significant reduction in infection level within one year among the semi-nomads. Being potentially curative in one intervention round, this combination should be considered for population group faced with challenges of achieving adequate coverage and adhesion to ivm MDA over prolonged period (>10 years)

Audit of the community-directed treatment with ivermectin (CDTI) for onchocerciasis and factors associated with adherence in three regions of Cameroon.

BACKGROUND: After more than 15 years of community-directed treatment with ivermectin (CDTI) in the Centre 1, Littoral 2 and West CDTI projects in Cameroon, the epidemiological evaluation conducted in 2011 revealed that onchocerciasis endemicity was still high in some communities. To investigate the potential reasons explaining this high endemicity, a cluster coverage survey was conducted in April-May 2015 in three health districts (HD), to assess the implementation of the CDTI, the 2014 therapeutic coverage and the five-year adherence to treatment. A two-stage cluster design was considered during analyses, with data weighted proportionally to age and gender distribution in the population. RESULTS: In the three HDs, 69 community leaders, 762 heads of households, 83 community drug distributors (CDD) and 2942 household members were interviewed. The CDTI organization and the involvement of heads of households were in average weak, with 84.0% (95% CI: 81.2-86.4%) of them who had not participated in activities during the 2014 mass drug administration (MDA). On average, six of ten community leaders declared that the period of treatment was decided by the health personnel while the CDDs selection was made during a community meeting for only 43.4% of them. The 2014 weighted therapeutic coverage was 64.1% (95% CI: 56.8-70.9%), with no significant difference in the three HDs. The survey coverages were lower than the reported coverages with a significant difference varying from 14.1% to 22.0%. Among those aged 10 years and above, 57.8% (95% CI: 50.2-65.1%) declared having taken the treatment each time during the last five MDAs with no significant difference among HDs, while 9.8% (95% CI: 7.5-12.8%) declared that they had never taken the drug. In multivariate analysis, the most important factors associated with the five-year adherence to treatment were high involvement in CDTI and age (40+ years). CONCLUSIONS: Despite more than 15 years of CDTI, there was still weak community participation and ownership, a lower coverage than reported and an average five-year adherence in the surveyed HDs. The reinforcement of the community ownership by the Ministry of Public Health officials and the timely procurement of ivermectin as requested by the communities are some measures that should be implemented to improve the therapeutic coverage, adherence to treatment and hence achieve onchocerciasis elimination. Further anthropological and entomological studies would provide better insights into our understanding of the persistence of the disease in these three CDTI projects

Important progress towards elimination of onchocerciasis in the West Region of Cameroon

Background: After more than a decade of community-directed treatment with ivermectin (CDTI) in the West Region of Cameroon, epidemiological evaluation conducted in 2011 showed that onchocerciasis endemicity was still high in some communities. The conceptual framework for onchocerciasis elimination recommends in such case, to conduct additional phase 1A surveys at intervals of three to four years. Therefore, to assess the progress made towards the elimination of onchocerciasis in the West CDTI projects, we conducted a cross-sectional survey in May 2015 in 15 unevaluated communities where the highest baseline endemicity level were found in 1996. All volunteers living for at least five years in the community, aged five years or more, underwent clinical and parasitological examinations. Individual adherence to ivermectin treatment was also assessed. Analyses of data were weighted proportionally to age and gender distribution in the population. Results: The mean age was 28.4 ± 22.2 years and there were 55% of women among the 2058 individuals examined. The weighted prevalences were 5.5%, 2.1% and 1.7% for microfilaridermia, nodule and cutaneous signs, respectively. The weighted microfilaridermia prevalences varied from 4.0 in 5-9 years old to 11.6% in 40-49 years old. In the 30 children under 10 years examined in Makouopsap, the weighted prevalences were 49.9% for microfilaridermia and 13.3% for nodule. In surveyed communities, the weighted prevalences varied from 0 to 41.6% for microfilaridermia, with 11 (73.3%) communities having <5%. Except Makouopsap which had 41.6%, all the surveyed communities were below 15% for microfilaridermia prevalence. The community microfilarial load (CMFL) expressed in microfilariae/skin snip (mf/ss), also significantly dropped by 98-100%, from 3.75-33.16 mf/ss in 1996 to 0-0.94 mf/ss in 2015. The weighted therapeutic coverage in 2014 was 69.4% and the 5 years' adherence was only 39.3% among participants. Conclusions: After more than 15 years of CDTI, there is an important progress towards the elimination of onchocerciasis in the communities surveyed. Innovative strategy like semi-annual ivermectin treatment plus vector control or the adjunction of a vector control strategy to the current annual treatment should be implemented in the bordering districts of the Centre and West Regions, as well as in other parts of the country with persistent high prevalences in the sight of onchocerciasis elimination.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Factors Associated with Ivermectin Non-Compliance and Its Potential Role in Sustaining <i>Onchocerca volvulus</i> Transmission in the West Region of Cameroon

<div><p>Background</p><p>Community Directed Treatment with ivermectin is the cornerstone of current efforts to eliminate onchocerciasis. However recent studies suggest there are foci where long-term annual distribution of the drug alone has failed to ensure elimination thresholds are reached. It is important to achieve high levels of compliance in order to obtain elimination targets. An epidemiological and entomological evaluation conducted in the western region of Cameroon in 2011 revealed that two health districts remained with a high prevalence of infection, despite long-term distribution of ivermectin since 1996. This paper explores potential factors that may have contributed to the non-interruption of transmission, focusing on ivermectin treatment compliance and the importance of systematic non-compliance within the population.</p><p>Methodology/Principal findings</p><p>A mixed methods approach was used, including a population-based survey to assess treatment compliance and factors associated and qualitative assessments including focus group discussions and in-depth interviews with key programme stakeholders and drug distributors. Compliance was reported at 71.2% (95%CI: 61.7–79.2%;n = 853/1198). The key factors related to compliance in the most recent round related to either programmatic and delivery issues, primarily absenteeism at the time of the campaign or alternatively individual determinants. An individual’s experience of side effects in the past was strongly associated with non-compliance to ivermectin. Other factors included ethnicity, how long lived in the village and age. There was a high percentage of reported systematic non-compliance at 7.4% (95% CI: 4.3–12.3%; n = 86/1165), higher amongst females. This group may be important in facilitating the sustainment of on-going transmission.</p><p>Conclusions/Significance</p><p>Efforts to reduce the number of systematic non-compliers and non-compliance in certain groups may be important in ensuring the interruption of transmission in the study area. However, in areas with high pre-control force of transmission, as in these districts, annual distribution with ivermectin, even if sustaining high levels of compliance, may still be inadequate to achieve elimination. Further studies are required to better understand the transmission dynamics and focus of on-going transmission in the study districts.</p></div

Geographic and therapeutic treatment rates in Massangam and Foumbot from 2004 to 2014.

<p>(Source: Respective district health officials, 2016).</p