Onchocerciasis: the pre-control association between prevalence of palpable nodules and skin microfilariae.

BACKGROUND: The prospect of eliminating onchocerciasis from Africa by mass treatment with ivermectin has been rejuvenated following recent successes in foci in Mali, Nigeria and Senegal. Elimination prospects depend strongly on local transmission conditions and therefore on pre-control infection levels. Pre-control infection levels in Africa have been mapped largely by means of nodule palpation of adult males, a relatively crude method for detecting infection. We investigated how informative pre-control nodule prevalence data are for estimating the pre-control prevalence of microfilariae (mf) in the skin and discuss implications for assessing elimination prospects. METHODS AND FINDINGS: We analyzed published data on pre-control nodule prevalence in males aged ≥ 20 years and mf prevalence in the population aged ≥ 5 years from 148 African villages. A meta-analysis was performed by means of Bayesian hierarchical multivariate logistic regression, accounting for measurement error in mf and nodule prevalence, bioclimatic zones, and other geographical variation. There was a strong positive correlation between nodule prevalence in adult males and mf prevalence in the general population. In the forest-savanna mosaic area, the pattern in nodule and mf prevalence differed significantly from that in the savanna or forest areas. SIGNIFICANCE: We provide a tool to convert pre-control nodule prevalence in adult males to mf prevalence in the general population, allowing historical data to be interpreted in terms of elimination prospects and disease burden of onchocerciasis. Furthermore, we identified significant geographical variation in mf prevalence and nodule prevalence patterns warranting further investigation of geographical differences in transmission patterns of onchocerciasis.

Characteristics of persons who complied with and failed to comply with annual ivermectin treatment.

OBJECTIVE: To assess individual compliance with annual ivermectin treatment in onchocerciasis-endemic villages. METHODS: Multi-site study in eight APOC-sponsored projects in Cameroon, Nigeria and Uganda to identify the socio-demographic correlates of compliance with ivermectin treatment. A structured questionnaire was administered on 2305 persons aged 10 years and above. Two categories of respondents were purposively selected to obtain both high and low compliers: people who took ivermectin 6-8 times and 0-2 times previously. Simple descriptive statistics were employed in characterizing the respondents into high and low compliers, while some socio-demographic and key perceptual factors were employed in regression models constructed to explain levels of compliance among the respondents. RESULTS: Some demographic and perceptual factors associated with compliance were identified. Compliance was more common among men (54.4%) (P < 0.001). Adults (54.6%) had greater rates of high compliance (P < 0.001. The mean age of high compliers (41.5 years) was significantly older (35.8 years) (t = 8.46, P < 0.001). Perception of onchocerciasis and effectiveness of ivermectin influenced compliance. 81.4% of respondents saw benefits in annual ivermectin treatment, high compliance among those who saw benefits was 59.3% compared to 13.3% of those who did not (P < 0.001). CONCLUSION: Efforts to increase compliance with ivermectin treatment should focus on providing health education to youth and women. Health education should also highlight the benefits of taking ivermectin.

Intention to continue with ivermectin treatment for onchocerciasis control after eight years of annual distribution in Cameroon, Nigeria, and Uganda.

This study identified the socio-demographic correlates of intention to comply with ivermectin treatment, from a structured interview of 2,306 persons aged 10 years and above, grouped into high and low compliers, who took ivermectin 6-8 times and 0-2 times respectively. Simple descriptive statistics were employed in characterizing the respondents into high and low compliers, while some socio-demographic and key perceptual factors were employed in regression models constructed to explain levels of compliance among the respondents. Demographic and perceptual factors associated with intention to comply with prolonged treatment with ivermectin were identified. Intention to comply was higher among married persons (91.8%, p < 0.001); local populations (89.8%, p < 0.001); and those with history of complying with treatment (98.2%, p < 0.001). Perception of onchocerciasis and effectiveness of ivermectin influenced intention to continue. The perceptual factors that drive the intention to comply should inform plans for health education at the project and village levels.

Compliance with eight years of annual ivermectin treatment of onchocerciasis in Cameroon and Nigeria.

BACKGROUND: As the African Programme for Onchocerciasis Control (APOC) matured into its 10th year of ensuring community involvement in mass annual treatment of onchocerciasis with ivermectin, there was recognition of a need to study not only annual coverage of ivermectin in villages but also the compliance of individual villagers with these annual treatments. This was based on the concern that while population coverage goals may be achieved each year, there might be segments of the population who systematically are not complying with the annual regimen, thus creating a reservoir of infection and threatening program gains. METHODS: A multi-site study in five APOC sponsored projects in Nigeria and Cameroon was undertaken to identify the socio-demographic correlates of compliance with ivermectin treatment. A total of 8,480 villagers above 9 years of age selected through a systematic random sampling from 101 communities were surveyed to ascertain their levels of compliance, by adapting APOC's standard household ivermectin survey form. Community leaders, community directed distributors (CDDs) of ivermectin and health workers were interviewed with in-depth interview guides, while focus group discussions were held with community members to help explain how socio-demographic factors might affect compliance. RESULTS: Eight-year compliance ranged from 0 to 8 times with 42.9% taking ivermectin between 6-8 times annually (high compliance). In bivariate analysis high compliance was positively associated with being male, over 24 years of age, having been married, not being Christian, having little or no formal education and being in the ethnic majority. These variables were also confirmed through regression analysis based on total times ivermectin was taken over the period. While these factors explained only 8% of the overall variation in compliance, ethnic status and education appeared to be the strongest factors. Those with higher education may be more mobile and harder to reach while neglect of ethnic minorities has also been documented in other programs. CONCLUSION: These findings can help managers of CDTI programmes to ensure ivermectin reaches all segments of the population equally.

Feasibility of measuring compliance to annual ivermectin treatment in the African Programme for Onchocerciasis Control.

The African Programme for Onchocerciasis Control (APOC) sponsors annual distribution of ivermectin to control onchocerciasis. Ivermectin should be taken annually by 65% of community members for a number of years to eliminate the disease as a public health problem. While many community coverage surveys have been undertaken during project monitoring, individual compliance could not be studied until several annual rounds of distribution had occurred. This paper reports on the efforts to determine whether adequate records could be found to enable a compliance study. A step-down process from project to district to community level was used to identify project sites where continuous ivermectin distribution up through 2004 had occurred. The first step consisted of selecting 17 of 25 projects by APOC. The second step determined adequacy of districts where distribution had occurred on a regular annual basis. Among 121 districts 58.6% undertook distribution in all 7 years. A total 852 villages were visited and community level records were found in all but three. Records showed that distribution had occurred for a minimum of five consecutive times in 429 villages, and ultimately 10 projects. While the feasibility study found an adequate number of villages to study compliance, the large number of projects, districts and villages that did not qualify for the follow-on compliance study should lead National Onchocerciasis Control Programme managers to strengthen the overall coverage and consistency of their efforts.