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A comparative study of several diagnostic measures applied in Guatemalan onchocerciasis

Abstract:

In 375 inhabitants of two fincas (=plantations) located in the high- and low-lands in a Guatemalan endemic focus of onchocerciasis, we compared the diagnostic measures developed in Guatemala. In the skin snippings, the microfilarial rate of males was higher than that of females in all age-groups. The microfilarial density per examinee was considered to be a more reliable index than MFD per microfilarial positive from the epidemiological aspect. Skin test (ST) using O. volvulus antigen revealed higher false positive reactions in comparison with other tests. The positive rate in ST was 82% in microfilarial negatives. Thus the result of ST was considered rather equivocal. Both the indirect hemagglutination test (IHA) and enzyme-linked immunosorbent assay (ELISA) using O. volvulus antigen and eluent of blood taken on filter paper were considered sensitive measures of immunodiagnosis which were adequately reflecting the intensity of infection (microfilarodermia). The results of IHA and ELISA showed high correlation. In contrast to the qualitative indices such as prevalence and incidence, the microfilarial density, IHA and ELISA were considered to be quantitative ones which reflected the intensity of infection in individuals. The merit of ELISA was stressed briefly.