Shigellosis: An emerging water-related public health problem

Abstract

Shigellosis, an old disease in new clothes, caused by Shigellae, has emerged as one of the major public health problems of particularly the developing regions. Shigellae are a group of microorganisms, which are spread through various routes including contaminated water and food. Shigellae are the third of most common pathogens transmitted through food. These cause dysentery, a clinical condition characterized by tenesmus (intestinal colicky pain) and the frequent passage of blood-stained mucopurulent stools. The Genus Shigella is grouped into four species: Shigella dysenteriae, Shigella boydi, Shigella flexneri, and Shigella sonnei. These species differ in geographic distribution, virulence, and drug susceptibility. Shigellosis is common in tropics and developing world due to poor hygiene, sanitation, high-risk behavior, and scarcity of water. The global disease burden due to Shigellosis is some 120 million cases, majority of these occur in the developing countries and involve children less than 5 years of age. 60 % of the deaths out of total of 1.1 million deaths each year occurring in children under 5 years of age are due to Shigella infection. Currently, Shigellosis disease burden is estimated to be at 90 million episodes and 108,000 deaths per year. About 500,000 cases of shigellosis are reported in addition, each year among military personnel and travellers from developed countries. Estimates of Shigellosis by ICCDRB, Bangladesh, show a small reduction in number of infections but marked decrease (90 %) in mortality compared to previous estimates. However, shigellosis has become a major health problem due to emergence of drug-resistant organisms, low infectivity dose (10 S. dysenteriae organisms), poor hygiene, and virulence. Humans and possibly some other primates are the reservoir for Shigellae. Currently, there is no effective vaccine, and the organism is reportedly increasingly developing resistant to the drugs like amoxicillin, cotrimoxazole, ampicillin, and chloramphenicol, etc. This is further adding to the problem of Shigellosis. Hence, it is prudent to include a chapter on Shigellae and Shigellosis in this tome on water and health.