Surveillance of shigellosis in rural Bangladesh: a 10 years review.

Over a period of 10 years 35,620 patients, admitted from a defined surveillance area, had a rectal swab culture done at a rural diarrhoea treatment centre in Bangladesh. Shigella spp. were isolated from 3,440 (9.7%) cases. Marked year to year variations were observed in isolation rates of Shigella spp. ranging from 5.7% to 16.7%. Sh. flexneri was the predominant isolate between 1978 to 1982 (56%-67%), Sh. dysenteriae type 1 predominated from 1983 to 1985 (45%-50%), and again Sh. flexneri became predominant in 1986 (55%) and 1987 (61%). Shigella were most commonly isolated from children aged 1-4 years followed by children 5-9 years and elderly people aged 45+ years. Sh. flexneri was isolated most frequently during August - January and Sh.dysenteriae type 1 during June to July. The overall case fatality rate in patients with shigellosis was 0.96%. It was 1.10% in children under 5 years of age. Prevalence of multiple antibiotic resistant strains increased over the years and at present most strains are resistant to commonly used antibiotics such as ampicillin and cotrimoxazole. Nalidixic acid is currently the drug of choice for Shigella infection in this area.