An outbreak of intestinal schistosomiasis, alongside increasing urogenital schistosomiasis prevalence, in primary school children on the shoreline of Lake Malawi, Mangochi District, Malawi

Abstract

Background: Intestinal schistosomiasis was not considered endemic in Lake Malawi until November 2017 when populations of Biomphalaria pfeifferi were first reported; in May 2018, emergence of intestinal schistosomiasis was confirmed. This emergence was in spite of ongoing control of urogenital schistosomiasis by preventive chemotherapy. Our current study sought to ascertain whether intestinal schistosomiasis is transitioning from emergence to outbreak, to judge if stepped-up control interventions are needed.Methods: During late-May 2019, three cross-sectional surveys of primary school children for schistosomiasis were conducted using a combination of rapid diagnostic tests, parasitological examinations and applied morbidity-markers; 1) schistosomiasis dynamics were assessed at Samama (n = 80) and Mchoka (n = 80) schools, where Schistosoma mansoni was first reported, 2) occurrence of S. mansoni was investigated at two non-sampled schools, Mangochi Orphan Education and Training (MOET) (n = 60) and Koche (n = 60) schools, where B. pfeifferi was nearby, and 3) rapid mapping of schistosomiasis, and B. pfeifferi, conducted across a further 8 shoreline schools (n = 240). After data collection, univariate analyses and Chi-square testing were performed, followed by binary logistic regression using generalized linear models, to investigate epidemiological associations.Results: In total, 520 children from 12 lakeshore primary schools were examined, mean prevalence of S. mansoni by ‘positive’ urine circulating cathodic antigen (CCA)-dipsticks was 31.5% (95% Confidence Interval (CI): 27.5–35.5). Upon comparisons of infection prevalence in May 2018, significant increases at Samama (Relative Risk (RR) = 1.7, 95% CI: 1.4–2.2) and Mchoka (RR = 2.7, 95% CI: 1.7–4.3) schools were observed. Intestinal schistosomiasis was confirmed at MOET (18.3%) and Koche (35.0%) schools, and in all rapid mapping schools, ranging from 10.0% to 56.7%. Several populations of B. pfeifferi were confirmed, with two new eastern shoreline locations noted. Mean prevalence of urogenital schistosomiasis was 24.0% (95% CI: 20.3–27.7). Conclusions: We notify that intestinal schistosomiasis, once considered non-endemic in Lake Malawi, is now transitioning from emergence to outbreak. Once control interventions can resume after coronavirus disease 2019 (COVID-19) suspensions, we recommend stepped-up preventive chemotherapy, with increased community-access to treatments, alongside renewed efforts in appropriate environmental control.

High prevalence of Schistosoma mansoni infection among adults with chronic non – communicable diseases in Malawi – a cross-sectional study at Mangochi District Hospital

“…This is the first study in Malawi to estimate the prevalence of S. mansoni infection in adults with NCDs. There was high prevalence of S. mansoni infection in this population which is consistent with estimates in school going children in the district of 10 – 56.7% (12). This is also consistent reports of an epidemic of both S. mansoni and S. haematobium in the district.…”

“…It has an NCD clinic that operates twice a week on Tuesdays (diabetes clinic) and Thursdays (hypertension clinic). Recent studies in Mangochi district have demonstrated an emerging epidemic of S. mansoni infection amid the increasing prevalence of S. haematobium infections in this setting (12).…”

“…This shift is no less dramatic than along the shores of Lake Malawi where the prevalence has gone from 0% before 2014 to 34.3% (95% CI 27.9 – 41.3) among school children in Mangochi in 2017 (6)(11). Follow up studies done after this period establish the emergence of S. mansoni as an epidemic in Mangochi district with prevalence among school children ranging from 10 – 56.7% (12).…”