# Liver and bladder morbidity in a Schistosoma mansoni and haematobium co-endemic area in the Democratic Republic of Congo

## TL;DR

This study found high rates of liver and bladder disease in a Congolese village where two types of schistosomiasis coexist, with mixed infections increasing bladder disease risk.

## Contribution

The study provides new insights into the health impacts of mixed Schistosoma infections in a co-endemic region of the DRC.

## Key findings

- Bladder morbidity was significantly higher in individuals with mixed Schistosoma infections compared to those with single S. haematobium infections.
- Liver morbidity was common but not significantly different between mixed and single S. mansoni infections.
- Age was a strong risk factor for both liver and bladder morbidity, with older individuals showing higher odds of disease.

## Abstract

Both Schistosoma (S.) mansoni and S. haematobium are co-endemic in many regions of the Democratic Republic of the Congo (DRC). However, little is known about the clinical implications of mixed Schistosoma infections for the affected communities. This study determined Schistosoma-related morbidity patterns in single and mixed Schistosoma infections in DRC.

Between November 2015 and March 2016, we conducted a community-wide study in the rural community of Kifwa II village, west of the DRC. According to WHO guidelines, Schistosoma-specific morbidity was assessed using ultrasound. Data were summarized using descriptive statistics, the Chi-square test, and logistic regression.

Ultrasound examinations were performed on 825 individuals aged 1–80 years. The results indicated that 68% (559) of the participants had bladder morbidity, with a higher prevalence observed in those with mixed infections compared to those with single S. haematobium infection (p = 0.001). The prevalence of liver morbidity was 64.6% (533), showing no difference between those with mixed and single S. mansoni infections (p = 0.174). Bladder morbidity was significantly associated with age, reflected by increasing odds ratios for different age groups: 1.6 (p = 0.035) for those aged 11–20 years, 1.7 (p = 0.046) for those aged 21–30 years, 2.2 (p = 0.005) for those aged 41–50 years, 3.2 (p = 0.001) for those aged 51–60 years, and 3.6 (p = 0.006) for those aged over 60 years. Similarly, liver morbidity was significantly associated with age, showing increasing odds ratios for different age groups: 1.7 (p = 0.026) for 21–30 years, 3.2 (p < 0.001) for 41–50 years, 4.5 (p < 0.001) for 51–60 years, and 3.1 (p = 0.011) for those over 60 years. However, mixed infection was associated with a significantly increased risk of bladder morbidity (aOR=2.3; p < 0.001), but not liver morbidity (aOR=1.4; p = 0.125).

Schistosoma-related morbidity is common in the study area, impacting individuals of all ages and calling for regular mass drug administration, considering the adult population, improved WASH infrastructure, and health education to encourage behavioural change. Additionally, mixed infections have a positive effect on bladder morbidity, with possible implications for disease control.

Schistosomiasis is a chronic and debilitating parasitic disease that affects 254 million people worldwide. Chronic infection with S. mansoni and S. haematobium can lead to organ damage of the liver and the urinary tract, respectively. Both species are endemic to the Democratic Republic of the Congo (DRC) and coexist in several regions, leading to the occurrence of mixed infections. However, little is known about the magnitude of liver and bladder schistosomiasis-related morbidity in these co-endemic areas and how this is affected by mixed infections. We investigated specific morbidity related to S. mansoni and S. haematobium in a co-endemic region and compared the risk of morbidity between people harboring mixed Schistosoma infections and those with single infections. For this, we screened 825 inhabitants of Kifwa II village in western DRC for Schistosoma infections and related specific organ morbidity. This study showed that liver and bladder morbidity were highly prevalent in this community, and affected all age groups. Also, bladder morbidity was more common in mixed infections than in single S. haematobium infections while mixed infections did not affect liver morbidity. The interaction effect between S. haematobium and S. mansoni on bladder morbidity could have implications for schistosomiasis control in the regions where both species coexist.