High Burden of Shigellosis Among Hospitalized Children under five in Ndola, Zambia: Evidence from molecular-based surveillance

Background Shigella spp. is a leading cause of moderate-to-severe diarrhea and diarrheal mortality in children under five (CU5), globally. Traditional culture-based techniques consistently underestimates its prevalence, particularly in high-burden regions of sub-Saharan Africa. We aimed to generate population-relevant estimates of shigellosis among hospitalized children under five (CU5) in Ndola, Zambia, using a sensitive molecular diagnostic approach. Methods A prospective, hospital-based surveillance study was conducted at Arthur Davison Children’s Hospital (ADCH) from May 2020 to November 2021. All CU5 admitted with acute diarrhea (≥2 watery stools/day) were eligible. From enrolled children, sociodemographic and clinical data were collected, and stool samples were obtained where possible. Primary detection of Shigella spp./enteroinvasive E. coli (EIEC) was performed using loop-mediated isothermal amplification (LAMP) targeting the conserved ipaH gene. Operational shigellosis case-definition: A child with diarrhea (2 or more watery stools/day) and a stool sample positive for the ipaH gene by LAMP. Prevalence of shigellosis was calculated among children with LAMP-tested samples and weighted to account for all admissions. The incidence of hospitalization was estimated using the district CU5 population denominators. Results Among 1,685 enrolled children, 950 provided stool samples. LAMP detected ipaH in 186 samples (19.6%;95% CI: 17.1–22.5). The weighted prevalence among all admissions was 19.5% (95% CI: 17.5–21.5) corresponding to 329 cases. The incidence of shigellosis hospitalization was 2.4 (95% CI: 2.2–2.7) per 1,000 person-years. The burden exhibited a distinct age distribution, peaking in children aged 12–23 months, preceded by an evident rise in the number of cases between 6 and 12 months of age. Shigellosis was associated with bloody diarrhea, increased stool frequency, and fever. Pre-admission antibiotic or other medication use was reported in 33% of cases. Conclusions Shigellosis accounts for a substantial proportion of severe diarrhea requiring hospitalization in Ndola, Zambia. Findings support improved diagnostics, antimicrobial stewardship, and prioritization of Shigella vaccines.