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

<p>Abstract</p> <p>Background</p> <p>As the African Programme for Onchocerciasis Control (APOC) matured into its 10^thyear 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.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>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.</p> <p>Conclusion</p> <p>These findings can help managers of CDTI programmes to ensure ivermectin reaches all segments of the population equally.</p

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

The Nigerian national blindness and visual impairment survey: Rationale, objectives and detailed methodology.

BACKGROUND: Despite having the largest population in Africa, Nigeria has no accurate population based data to plan and evaluate eye care services. A national survey was undertaken to estimate the prevalence and determine the major causes of blindness and low vision. This paper presents the detailed methodology used during the survey. METHODS: A nationally representative sample of persons aged 40 years and above was selected. Children aged 10-15 years and individuals aged <10 or 16-39 years with visual impairment were also included if they lived in households with an eligible adult. All participants had their height, weight, and blood pressure measured followed by assessment of presenting visual acuity, refractokeratomery, A-scan ultrasonography, visual fields and best corrected visual acuity. Anterior and posterior segments of each eye were examined with a torch and direct ophthalmoscope. Participants with visual acuity of < = 6/12 in one or both eyes underwent detailed examination including applanation tonometry, dilated slit lamp biomicroscopy, lens grading and fundus photography. All those who had undergone cataract surgery were refracted and best corrected vision recorded. Causes of visual impairment by eye and for the individual were determined using a clinical algorithm recommended by the World Health Organization. In addition, 1 in 7 adults also underwent a complete work up as described for those with vision < = 6/12 for constructing a normative data base for Nigerians. DISCUSSION: The field work for the study was completed in 30 months over the period 2005-2007 and covered 305 clusters across the entire country. Concurrently persons 40+ years were examined to form a normative data base. Analysis of the data is currently underway. CONCLUSION: The methodology used was robust and adequate to provide estimates on the prevalence and causes of blindness in Nigeria. The survey would also provide information on barriers to accessing services, quality of life of visually impaired individuals and also provide normative data for Nigerian eyes

Association between prevalence of nodules in adult males and skin mf in the general population.

<p>Colored symbols represent data from seven geographical areas. Colored ellipses indicate the 95% percentiles (Z = 1.96) of the predicted joint distributions of infection prevalences within each geographical area, based on the estimated variances and correlation of observations within geographical areas. Black symbols represent the mean infection prevalences in each of the geographical areas. The black ellipse represents the 95% percentile of the joint distribution of mean infection prevalences in geographical areas, illustrating the deviating pattern in nodule and mf prevalence in Mbam, Cameroon (black and brown crosshairs and brown ellipse). Predictions were based on a Bayesian hierarchical multivariate logistic regression model with a fixed effect for Mbam, Cameroon, and random effects for other geographical areas.</p

Comparison of observations (x-axis) versus model predictions (y-axis).

<p>The comparison was made by means of mixed posterior predictive checks of the numbers of individuals with detectable microfilariae in the skin and adult males with nodules. The dotted diagonal line represents the hypothetical perfect model fit. Error bars represent the 95% Bayesian prediction interval for the numbers of adult males with nodules and individuals with detectable microfilariae in the skin each village, and should intersect with the diagonal line if the model fit is good.</p

Locations of study sites.

<p>Locations of study sites.</p

Predicted skin mf prevalence in the general population, given observed nodule prevalence in adult males.

<p>Symbols represent observed data by geographical area. Within each set of regression lines, the middle and outer lines relate to the median and 95% Bayesian credible intervals of the posterior predictive distribution, respectively (black set for areas all areas but Mbam; grey set for Mbam, the only forest-savanna mosaic area). Predictions were made assuming that nodule prevalence was based on a sample of 30 adult males.</p

Characteristics of data used for modeling the association between prevalence of nodules and microfilariae.

<p><i>s.s.</i>: sensu stricto.</p