Epidemiology of Schistosoma mansoni infection in Ituri Province, North-eastern Democratic Republic of the Congo
Authors: Nigo Maurice M , Odermatt Peter , Salieb-Beugelaar Georgette B. , Morozov Oleksii , Battegay Manuel , Hunziker Patrick R 
Published: August 2020

Background

Schistosomiasis, caused by Schistosoma mansoni, is of great significance to public health in sub–Saharan Africa. In the Democratic Republic of Congo (DRC), information on the burden of S. mansoni infection is scarce, which hinders the implementation of adequate control measures. We assessed the geographical distribution of S. mansoni infection across Ituri province in north-eastern DRC and determined the prevailing risk factors.

Methods / Principal Findings

Two province–wide community–based studies were conducted. First, in 2016, a geographical distribution study was carried out in 46 randomly selected villages, covering 12 of the 36 health districts across Ituri. Second, in 2017, an in–depth study was conducted in 12 purposively-selected villages, across six health districts. In each study village, households were randomly selected and members, aged one year and older and present on the survey day, were enrolled. In 2016, one stool sample was collected per participant, while in 2017, several samples were collected per participant. S. mansoni eggs were detected using the Kato–Katz technique. The 2017 study also incorporated a point–of–care circulating cathodic S. mansoni antigen (POC–CCA) urine test. Household and individual questionnaires were used to collect data on demographic, socioeconomic, environmental, behavioural and knowledge risk factors.

The 2016 study included 2,131 participants, 40.0% of whom had S. mansoni infections. Infection prevalence in the villages ranged from 0 to 90.2%. The 2017 study included 707 participants, of whom 73.1% tested positive for S. mansoni. Infection prevalence ranged from 52.8 to 95.0 % across the health districts visited. In general, infection prevalence increased from north to south and from west to east. Exposure to the waters of Lake Albert and the villages’ altitude above sea level were associated with the distribution.

Both men and women had the same infection risk (odds ratio [OR] 1.2, 95% confidence interval [CI] 0.82-1.76). Infection prevalence and intensity peaked in the age groups between 10 and 29 years. Preschool children were highly infected (62.3%). Key risk factors were poor housing structure (OR 2.1, 95% CI 1.02-4.35), close proximity to water bodies (OR 1.72, 95% CI 1.1-2.49), long–term residence in a community (OR 1.41, 95% CI 1.11-1.79), lack of latrine in the household (OR 2.00, 95% CI 1.11-3.60), and swimming (OR 2.53, 95% CI 1.20-5.32) and washing (OR 1.75, 95% CI 1.10-2.78) in local water bodies. A family history of schistosomiasis (OR 0.52, 95%, 95% CI 0.29-0.94) and knowledge of praziquantel treatment (OR 0.33, 95% CI 0.16-0.69) were protective risk factors, while prevention knowledge (OR 2.35, 95% CI 1.36-4.08) was associated with increased infection risk.

Conclusions/Significance

Our results confirm high endemicity of S. mansoni in Ituri province, DRC. Both the prevalence and intensity of infection, and its relationship with the prevailing socioeconomic, environmental, and behavioural risk factors indicate intense exposure and alarming transmission levels. The study findings warrant control interventions that pay particular attention to high–risk communities and population groups, including preschool children.

Author Summary

Intestinal schistosomiasis threatens many people in the tropical world, particularly those in Sub–Saharan Africa. Information on schistosomiasis in the Democratic Republic of Congo (DRC) is very scarce, which is a major barrier to planning and implementing efficient control programmes.

We conducted two community–based studies with the objective of assessing the geographical distribution of S. mansoni infection across the Ituri province in north-eastern DRC and determining the prevailing risk factors. In 2016, a geographical distribution study was carried out in 46 randomly selected villages across the province. In 2017, an in–depth study was conducted in 12 purposively selected villages. In both studies, households were randomly selected and members, aged one year and older and present on the survey day, were enrolled. In 2016, one stool sample was examined per participant, whereas several stool samples were examined for each participant in 2017. S. mansoni eggs were detected using the Kato–Katz technique. The 2017 study also included a point–of–care circulating cathodic S. mansoni antigen (POC–CCA) urine test. Household and individual questionnaires were used to collect data on demographic, socioeconomic, environmental, behavioural and knowledge risk factors. The 2016 study included 2,131 participants, 40.0% of whom had S. mansoni infections. The 2017 study included 707 participants, of whom 73.1% tested positive for S. mansoni. In general, infection prevalence increased from north to south and from west to east. Exposure to the waters of Lake Albert and villages’ altitude above sea level were main drivers of the distribution. A risk factor analysis revealed that both men and women had the same infection risk. Infection prevalence and intensity peaked in the age groups between 10 and 29 years. Preschool children were highly infected (62.3%). We identified the main risk factors to be poor housing structure, proximity to water bodies, long–term residence in a community, lack of latrine in the household, and swimming and washing in local water bodies. A family history of schistosomiasis and knowledge of praziquantel treatment were protective risk factors, while prevention knowledge was associated with increased infection risk. Our results confirm that S. mansoni is highly endemic in Ituri province, DRC. Both infection prevalence and intensity, and its relationship with the prevailing socioeconomic, environmental, and behavioural risk factors indicate intense exposure and alarming transmission. Control interventions are warranted and should pay attention to high–risk communities and population groups, including preschool children.