SHIGELLA DYSENTERIAE AND SH. FLEXNERI SEROTYPE PREVALENCE AND SEASONAL DISTRIBUTION IN ADDIS ABABA, ETHlOPIA

Abstract

ABSTRACT

A total of 945 Shigella strains were isolated from stool specimens received at the National Research Institute of Health, between January 1978 and I£cember 1985. Seven hundred and ftfty-two strains, belonging to Shigella dysenteriae and Sh. flexneri, were further identified to serotype level, and the results analysed in respect to their annual fluctuation over an 8-year period. Their seasonal distributon was also noted.

Members of Sh. dysenteriae serotypes constituted 24.3% of total Shigella isolates. Within Sh. dysenteriae serotypes, type 1 followed by type 2 were dominant until 1984, when type 3 predominated. In 1985, types 1,2 and 3 were equally represented.

Members of Sh. flexneri comprised 56.3% of total Shigella isolates. Unti11981, type 1 was dominant, followed by types 2 and 4, in that order. Since then, however, type 1 gave way to type 2, as the dominant Shigella flexneri serotype in Addis Ababa area. The internationally rare serotype 5 was encountered only once ,on 1981.
Shigella infections were comparatively common during the months of April to June, and around the month of September. Its incidence was lowest at the height

of the rainy season (July, August) and during the colder months of the year (December to january). The seasonal fluctuation of Shigella seemed to be influenced more by Sh. flexneri than by Sh. dysenteriae.