Human onchocerciasis in the lower Jos Plateau, central Nigeria: the prevalence, geographical distribution and epidemiology in Akwanga and Lafia local government areas

The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (1) priority areas for ivermectin treatment

Background

The African Programme for Onchocerciasis Control (APOC) was created to control onchocerciasis as a public health problem in 20 African countries. Its main strategy is community directed treatment with ivermectin. In order to identify all high risk areas where ivermectin treatment was needed, APOC used Rapid Epidemiological Mapping of Onchocerciasis (REMO). REMO has now been virtually completed and we report the results in two articles. The present article reports the mapping of high risk areas where onchocerciasis was a public health problem. The companion article reports the results of a geostatistical analysis of the REMO data to map endemicity levels and estimate the number infected.

Methods

REMO consists of three stages: exclusion of areas that are unsuitable for the vector, selection of sample villages to be surveyed in each river basin, and examination of 30 to 50 adults for the presence of palpable onchocercal nodules in each selected village. The survey results and other relevant information were processed in a geographical information system. A panel of experts interpreted the data taking the river-based sampling into account and delineated high risk areas where the prevalence of nodules is greater than 20%.

Results

Unsuitable areas were identified in eight countries. In the remaining areas surveys were done in a total of 14,473 sample villages in which more than half a million people were examined. High-risk areas were identified in 18 APOC countries, ranging from small isolated foci to a vast contiguous endemic area of 2 million km² running across seven countries. In five countries the high risk area covered more than 48% of the total surface area, and 31% to 48% of the population. It is estimated that 86 million people live in high risk areas in the APOC countries.

Conclusions

The REMO maps have played a significant role in onchocerciasis control in the 20 APOC countries. All high-risk areas where onchocerciasis used to be a serious public health problem have been clearly delineated. This led to the creation of community-directed treatment projects that by 2012 were providing annual ivermectin treatment to over 80 million people.

CD4(+), CD8(+), immunoglobulin status and ocular lesions among some onchocerciasis-infected rural Nigerians

CD4(+), CD8(+), immunoglobulin status and ocular lesions of some onchocerciasis-infected rural Nigerians as manifested by the presence of microfilariae in their skin snips and some chronic symptoms of the parasitic infestation were evaluated. The highest mean CD4(+) and mean microfilarial (mff) load of 560 +/- 20.46 unit cells/microl and 20 mff/mg were recorded among the individuals within the second decade of life, while the least mean CD4+ and mff load of 307.20 +/- 11.23 unit cell/microl and 6.5 mff/mg occurred among volunteers after 60 years of age. The highest mean CD8(+) of 388.00 +/- 23.71 unit cells/microl occurred at the third decade of life. The individuals above 60 years had the least mean CD8(+) of 350.25 +/- 11.90 unit cells/microl. The volunteers had mean CD4(+) of 372.45 +/- 109.02 unit cells/microl and mean CD8(+) of 359.42 +/- with an overall CD4(+):CD8(+) ratio of 1.04. The mean CD4(+) and mean CD8(+) had positive correlation with the mean microfilarial load (r = 0.52 and r = 0.40), respectively. The mean IgE, IgG, lgA, IgM, and IgD were 2,074.82 +/- 823.09, 19.36 +/- 2.49, 3.88 +/- 0.26, 3.59 +/- 0.38, and 0.29 +/- 0.19 mg/dl, and these immunoglobulins negatively correlated with the mean microfilarial load at r = -0.02, r = -0.15, r = -0.82, r = -0.37, and r = 0.26, respectively. Among these immunoglobulins evaluated, only mean IgE (2,074.82 +/- 823 ng/ml) was statistically different from the control subjects (0 mg/dl) at t = 3.39, P < 0.05. In all, the prevalence of the visual impairment and lesions were low. Among the six visual lesions, namely, cataract, choroidoretinitis, iridocyclitis, glaucoma, sclerosing keratitis, and optic atrophy encountered in Egoro-Eguare, only optic atrophy and sclerosing keratitis was reported among the children. The female adults had the highest prevalence of reduced vision 20(43.5%). Also, the prevalence of choroidoretinitis (2.2%) and iridocyclitis (2.2%) were the least prevalent ocular lesions reported among these female adults. The depletion of the CD4(+) contributed to the low prevalence of visual impairment and lesions in this locality. The depleted CD4(+), CD8(+), and the lower values of IgA, IgM, and IgG contributed in the maintenance of chronicity of onchocerciasis in Egoro-Eguare, Nigeria.