Browsing by Author "Cohen D"

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    Sensitivity and predictive value of dysentery in diagnosing shigellosis among under five children in Zambia.
    (2023) Miti S; Chilyabanyama ON; Chisenga CC; Chibuye M; Bosomprah S; Mumba C; Chitondo S; Siziya S; Cohen D; Chilengi R; Simuyandi M; Center for Infectious Disease Research in Zambia, Lusaka, Zambia.; Arthur Davison Children's Hospital, Ndola, Zambia.; School of Public Health, Tel Aviv University, Tel Aviv, Israel.; Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana.; Tropical Diseases Research Center, Ndola, Zambia.; School of Medicine, Copperbelt University, Ndola, Zambia.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
    BACKGROUND: Shigella is a leading cause of bacterial diarrhea morbidity and mortality affecting mainly children under five in the developing world. In Zambia, Shigella has a high prevalence of 34.7% in children with diarrhea and an attributable fraction of 6.7% in Zambian children with moderate to severe diarrhea. Zambian diarrhea management guidelines and the health ministry reporting tool Health Management Information System (HMIS) heavily rely on the WHO clinical classification of dysentery to potentially identify and estimate the burden of Shigella in children. This reliance on clinical dysentery as a proxy to shigellosis in under five children may be resulting in gross under-estimation of shigella disease burden in Zambia. METHODS: We used existing laboratory and clinical data to examine the sensitivity and predictive value of dysentery to correctly identify Shigella infection in under five children with PCR confirmed Shigella infection in Lusaka and Ndola districts, Zambia. RESULTS: Clinical dysentery had a sensitivity of 8.5% (34/401) in identifying under five children with Shigella by stool PCR. Dysentery was able to correctly classify Shigella in 34 of 68 bloody stool samples giving a corresponding positive predictive value of 50%. Of the 1087 with non-bloody diarrhea, 720 did not have Shigella giving a negative predictive value of 66.2%. CONCLUSIONS: Use of clinical dysentery as a screening symptom for Shigella infection in children under five presenting with moderate to severe diarrhea has low sensitivity and low positive predictive value respectively. Clinical dysentery as a screening symptom for Shigella contributes to gross under diagnosis and reporting of Shigella infection among under five children in Zambia. Further research is required to better inform practice on more accurate methods or tools to use in support of routine diagnosis, particularly in low middle-income settings where laboratory diagnosis remains a challenge.
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    Shigella-specific antibodies in the first year of life among Zambian infants: A longitudinal cohort study.
    (2021) Chisenga CC; Bosomprah S; Simuyandi M; Mwila-Kazimbaya K; Chilyabanyama ON; Laban NM; Bialik A; Asato V; Meron-Sudai S; Frankel G; Cohen D; Chilengi R; Imperial College London, London, United Kingdom.; School of Public Health, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.; Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.; Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
    INTRODUCTION: Shigellosis, is a leading cause of moderate-to-severe diarrhoea and related mortality in young children in low and middle income countries (LMICs). Knowledge on naturally acquired immunity can support the development of Shigella candidate vaccines mostly needed in LMICs. We aimed to quantify Shigella-specific antibodies of maternal origin and those naturally acquired in Zambian infants. METHODS: Plasma samples collected from infants at age 6, 14 and 52-weeks were tested for Shigella (S. sonnei and S. flexneri 2a) lipopolysaccharide (LPS) antigen specific immunoglobulin G (IgG) and A (IgA) by enzyme-linked immunosorbent assay. RESULTS: At 6 weeks infant age, the IgG geometric mean titres (GMT) against S. sonnei (N = 159) and S. flexneri 2a (N = 135) LPS were 311 (95% CI 259-372) and 446 (95% CI 343-580) respectively. By 14 weeks, a decline in IgG GMT was observed for both S. sonnei to 104 (95% CI 88-124), and S. flexneri 2a to 183 (95% CI 147-230). Both S. sonnei and S. flexneri 2a specific IgG GMT continued to decrease by 52 weeks infant age when compared to 6 weeks. In 27% and 8% of infants a significant rise in titre (4 fold and greater) against S. flexneri 2a and S. sonnei LPS, respectively, was detected between the ages of 14 and 52 weeks. IgA levels against both species LPS were very low at 6 and 14 weeks and raised significantly against S. flexneri 2a and S. sonnei LPS in 29% and 10% of the infants, respectively. CONCLUSION: In our setting, transplacental IgG anti-Shigella LPS is present at high levels in early infancy, and begins to decrease by age 14 weeks. Our results are consistent with early exposure to Shigella and indicate naturally acquired IgG and IgA antibodies to S. flexneri 2a and S. sonnei LPS in part of infants between 14 and 52 weeks of age. These results suggest that a potential timing of vaccination would be after 14 and before 52 weeks of age to ensure early infant protection against shigellosis.