The use of a topical Mazzotti test in the diagnosis of onchocerciasis.

The use of locally applied 1.6% diethylcarbamazine citrate in Nivea lotion as a diagnostic test for onchocerciasis was studied in 473 Liberians aged 2 to 55 years. The lotion was administered on an area of skin of 10 X 10 cm. Only papular reactions were considered as positive test results. The sensitivity of the test increased significantly with higher microfilaria densities and was higher in a hyperendemic area than in hypoendemic villages. No correlations were found between sensitivity and age and between intensity of papular reactions and microfilaria densities. Positive test results in persons without microfilariae in their skin snips produced only a minor increase of 2-3% in prevalence figures. Predictive values were calculated for different degrees of endemicity. They show that under certain conditions the topical Mazzotti test can be a simple and useful test. However, it cannot replace the search for microfilariae in skin snips.