Shigellosis, prevalent worldwide, is still a major cause of childhood mortality in developing countries. An estimated 667,000 children, aged less than five years, die due to Correspondence and reprint requests should be addressed to: Dr. S.K. Roy Scientist ICDDR,B: Centre for Health and Population Research GPO Box 128, Dhaka 1000 Bangladesh Email: firstname.lastname@example.org Fax: 880-2-8823116, 8812530 shigellosis each year in developing countries (1). In Bangladesh, Shigella dysenteriae causes epidemic dysentery and is associated with more complications than other Shigella species, and S. flexneri is responsible for endemic infection. Malnutrition is another major publichealth problem in developing countries (2), and interaction of malnutrition with shigellosis leads to an even higher mortality (3). Shigellosis causes malnutrition, which is enhanced through reduced food intake (4), increased energy expenditure as a consequence of systemic effects of inflammation and fever, malabsorption, and enteric loss of protein (5).
Hypothermia, severe malnutrition, severe dehydration, altered consciousness, abdominal distension, thrombocytopaenia, hypoproteinaemia, hyponatraemia, hypoglycaemia, renal failure, and bacteraemia are significantly more common in patients with Shigella-associated infection (6). Complications due to shigellosis, such as malnutrition, pneumonia, and septicaemia, predispose children to a higher risk of mortality (7). Frequent resistance to antibiotics (8) and absence of effective vaccines impede the treatment of shigellosis. Although risk factors for the death of children with shigellosis have been described before (6,9), it was not specific for severelymalnourished children. As severe malnutrition is significantly associated with deaths due to dysentery (9), it is necessary to identify the risk factors for mortality of severely-malnourished children to reduce preventable deaths.
We hypothesized that severely-malnourished children, who die of shigellosis, present with some particular characteristics compared to those who are discharged alive. Therefore, to determine the factors responsible for increased mortality, we undertook a case-control study using the hospital records of 200 patients with lethal S. dysenteriae type 1 or S. flexneri-associated infection admitted to the Clinical Research and Service Centre of ICDDR,B: Centre for Health and Population Research during December 1993_January 1999. Of these patients, 100 died in the hospital, and the remaining 100 matched patients were discharged alive.
MATERIALS AND METHODS
Although all Shigella species are endemic in Bangladesh, S. flexneri and S. dysenteriae are the most commonly- isolated species from culture of stools of patients who attended the treatment centre of ICDDR,B during 1983-1987 (6). These two also cause a more severe form of dysentery with more gastrointestinal and extraintestinal manifestations than S. boydii and S. sonnei (10,11).
The hospital records of patients admitted to the Clinical Research and Service Centre of ICDDR,B during December 1993_January 1999 were reviewed. The Centre treated more than 150,000 diarrhoeal patients in 1998. Approximately, 10,000 of them had a positive culture for Shigella. Death cases were selected from those cases who died due to shigellosis in the hospital. The probability for the controls to have a risk factor was estimated to be 10%. We planned to identify a risk factor with an odds ratio of size 2.5 or more. This sample size is adequate for 95% level of significance and 80% power of the test. One hundred cases were selected by calculating the sample size. Death cases and controls were selected after matching with the major criteria. Every case was compared with a control, leading to a total sample size of 200 (12).
Patients who attended the Centre were mainly of low socioeconomic status and came either from Dhaka city or from its surrounding areas. Patients with severe diarrhoea or dysentery with complications, such as pneumonia, suspected sepsis, severe malnutrition, or patients of extreme age, such as infants, and those aged over 65 years, were hospitalized. …