Objectives: To assess the potential risk factors for shigellosis including housefly density.
Methods: A matched case-control study to investigate potential risk factors for shigellosis was conducted in a semi-urban area, Kaengkhoi District, Saraburi Province, central Thailand. Shigella cases were ascertained from a two-year population-based surveillance study detecting diarrhea and shigellosis in the area. The study evaluated a wide range of exposures, which were assessed by odds ratios (OR) adjusted for proxy markers of socioeconomic status: family income, and type of residence, using conditional logistic regression analysis.
Results: Hygiene behaviors such as regular hand washing (p<0.05), a clean environment surrounding the household (p<0.001), and the availability of water to flush the toilet (p=0.08) were associated with a reduced risk for shigellosis in the multivariate model. In contrast factors indicating a lower than average socioeconomic status, such as having to rent instead of owning one's housing (p<0.001) and a low family income (p<0.01) were associated with an increased risk for shigellosis. For children, breastfeeding showed a strong protective effect in reducing the risk of shigellosis (p<0.01). Prior to adjustment for environmental factors, fly density in the kitchen area was associated with an increased risk of shigellosis (p<0.01).
Conclusions: We found a correlation between socioeconomic status and the risk for shigellosis. To reduce shigellosis in this setting, we recommend interventions focused on three aspects: improved water supply and sanitation (especially latrines and garbage disposal) including fly control, health education on hand washing, and the promotion of breastfeeding.