Blinding Onchocerciasis in Pader District, Northern Uganda

Watmon B, Lakwo T L, Onapa A W


Background: Onchocerciasis is caused by a filarial nematode Onchocerca volvulus, and is transmitted by a female black fly of the genus Simulium which breeds in fast flowing rivers. In Uganda, the disease is endemic in 37 districts with clinical manifestations mainly on the skin. The long-term armed conflict in northern Uganda made research and control of onchocerciasis in the region and particularly Pader district receive little attention. There have been no attempts to establish the magnitude of the disease in the region.

Objective: To establish the magnitude and clinical manifestations of Onchocerciasis in Pader district, northern Uganda.

Methods: Twenty parishes in sub counties with Rapid Epidemiological Mapping of Onchocerciasis (REMO) nodule prevalence of 25.0% or more were randomly sampled and 675 persons consecutively enrolled in 13 parishes. The respondents underwent dermatological, parasitological and ocular examinations.

Results: A total of 675 persons were examined and of these, 318 had skin snipping and microscopy done. The prevalence of microfilaria (mf) in skin snip was 29.6% (95% CI: 24.6%-34.6%) while prevalence of nodules was 30.1% (95% CI: 3.1%-6.5%). The prevalence of microfilaria in the anterior chamber of the eye (MFAC) was 4.1% (95% CI: 2.6%-5.6%) and that of reversible ocular lesions was 4.0% (95% CI: 2.5%-5.5%). The reversible ocular lesions of onchocerciasis observed were punctate keratitis stage B (PKB, 0.1%), punctate keratitis stage D (PKD, 0.1%) and punctate keratitis stage E (PKE, 3.7%) while the irreversible ocular lesions were observed in 16.1% (95% CI: 13.3%-18.9%) of the respondents. The most important irreversible lesions were optic atrophy 6.4%, (95% CI: 3.7%-9.1%) and sclerosing keratitis, 5.2% (95% CI: 2.8%-7.6%). Visual impairment was detected in 29.2% (95% CI: 25.8%-32.6%) of the respondents and the main causes were cataracts (27.4%) and optic atrophy (21.8%). The association between irreversible lesion and visual loss (p< 0.00) and irreversible lesions and nodules (p< 0.00) were both significant.

Conclusion: This study indicates that the onchocerciasis in Pader district is the blinding type. There is need to strengthen health education, community social mobilization and start biannual Mass Drug Administration (MDA) with Ivermectin.

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