[Seroepidemiologic study of human plague in Madagascar]

An IgG anti-F1 Enzyme linked immunosorbent assay (Elisa) has been developed for plague diagnosis in the Malagasy republic. The sensitivity of the test was 91.4% and the specificity 98.5%. This technique is cheap and the cross reaction with other infections diseases prevalent in Madagascar is very limited. During the urban plague outbreak (Mahajanga city, 1995), the positive predictive value and the negative predictive value were 95.2% and 97% respectively. During this outbreak, the usefulness of the Elisa test for retrospective individual serodiagnosis was confirmed. Furthermore, the test confirmed plague among suspect patients without bacteriological diagnosis. The test was used for a sero-epidemiological study. Eight villages in the endemic area were investigated and 900 persons were studied. The overall seroprevalence was 6 times the officially prevalence of plague, notified at the Central Plague Laboratory. A large disparity of the seroprevalence was observed in the endemic area, with variation from < 1.5% to 15.5%. A high incidence of asymptomatic infections due to Yersinia pestis was found.