Micro-Geographical Heterogeneity in Schistosoma mansoni and S. haematobium Infection and Morbidity in a Co-Endemic Community in Northern Senegal

Abstract

Background Schistosoma mansoni and S. haematobium are co-endemic in many areas in Africa. Yet, little is known about the micro-geographical distribution of these two infections or associated disease within such foci. Such knowledge could give important insights into the drivers of infection and disease and as such better tailor schistosomiasis control and elimination efforts.MethodologyIn a co-endemic farming community in northern Senegal (346 children (0–19 y) and 253 adults (20–85 y); n = 599 in total), we studied the spatial distribution of S. mansoni and S. haematobium single and mixed infections (by microscopy), S. mansoni-specific hepatic fibrosis, S. haematobium-specific urinary tract morbidity (by ultrasound) and water contact behavior (by questionnaire). The Kulldorff's scan statistic was used to detect spatial clusters of infection and morbidity, adjusted for the spatial distribution of gender and age.Principal Findings Schistosoma mansoni and S. haematobium infection densities clustered in different sections of the community (p = 0.002 and p = 0.023, respectively), possibly related to heterogeneities in the use of different water contact sites. While the distribution of urinary tract morbidity was homogeneous, a strong geospatial cluster was found for severe hepatic fibrosis (p = 0.001). Particularly those people living adjacent to the most frequently used water contact site were more at risk for more advanced morbidity (RR = 6.3; p = 0.043).Conclusions/Significance Schistosoma infection and associated disease showed important micro-geographical heterogeneities with divergent patterns for S. mansoni and S. haematobium in this Senegalese community. Further in depth investigations are needed to confirm and explain our observations. The present study indicates that local geospatial patterns should be taken into account in both research and control of schistosomiasis. The observed extreme focality of schistosomiasis even at community level, suggests that current strategies may not suffice to move from morbidity control to elimination of schistosomiasis, and calls for less uniform measures at a finer scale.

Schistosoma haematobium co-infection with soil-transmitted helminthes: prevalence and risk factors from two communities in the central region of Ghana

“…However, comparison of some reported prevalence estimates for S. haematobium infection from some communities together with the present prevalence estimate, it is tempting to speculate that average prevalence rate of S. haematobium infection in Ghana may be high despite increasing national efforts in terms of education and mass treatment. Compared with S. haematobium infectionprevalence estimates from some studied communities in some African countries such as in Malawi (10.4 %), [26] Sudan (0.0 %), [27] Senegal, [28] and Kenya (9.3 %), [29] that of the present study is relatively high despite been lower compared to estimates from communities in Zimbabwe (68 %), [29] Nigeria (51-59.5 %), [31,32] and Benue state in Nigeria (41.5 %). [5] S. haematobium co-infection with S. mansoni and other soil-transmitted helminthes is reported elsewhere.…”

Understanding wetlands reclamation and soil-transmitted helminths and schistosomiasis incidence patterns in Rwanda (2001-2012)

“…One such study identified a 'new' area with the high rates of schistosomiasis (Isabwe et al, 2012), which was not detected before by the national prevalence study. The latter confirms the general recommendation of prevalence based studies in Rwanda or elsewhere in Africa (Meurs et al, 2013;Standley et al, 2009) that more detailed information is required to address the often highly focalized spatial pattern of schistosomiasis hotspots. The same studies also recommend to include other high-risk community groups (e.g.…”

High Schistosoma mansoni Disease Burden in a Rural District of Western Zambia

“…Microgeographical variations in schistosomiasis-endemic areas have been documented [27][28][29] and are probably caused by factors, such as differences in transmission dynamics involving both the intermediate snail host and the human host. 30,31 The variations in infection distributions in different communities have implications for control activities, because affected areas may require targeted interventions as opposed to mass interventions.…”