Conducted jointly by UAC and UPVD, this research reveals the dynamics of schistosomiasis in Benin.
The Essentials: Conducted jointly by UAC and UPVD, this research reveals the dynamics of schistosomiasis in Benin.
Moudachirou Ibikounle (Université d’Abomey-Calavi = University of Abomey Calavi [Cotonou, Bénin]).
Thesis defended in 2006 at the doctoral school Biology, Environment and Engineering Sciences (Perpignan); Life Sciences (Abomey-Calavi).
This research was carried out under a Franco-Beninese joint supervision (cotutelle), ensuring simultaneous grounding in local field realities and international academic standards.
Context and Research Question
Schistosomiasis is a major public health problem in Benin, affecting a significant share of the population. According to epidemiological data, the prevalence of S. haematobium reaches 85%, while that of S. mansoni stands at 30%. These figures underscore the importance of research on these parasites, which have implications not only for human health but also for the country's socioeconomic development. Benin, as a member of the Economic Community of West African States (ECOWAS), faces challenges similar to those observed in other countries in the region, where schistosomiasis is endemic.
Studying the epidemiology and host-parasite interactions is crucial for a thorough understanding of transmission dynamics and the factors influencing the spread of schistosomiasis. Analyzing the mollusk vectors, particularly species of the genus Bulinus, is fundamental for assessing transmission risks and implementing effective control strategies.
Methodology
This research relies on a combined epidemiological and ecological approach. A literature review was carried out to examine the state of knowledge on schistosomiasis within the ECOWAS region. Field surveys collected data on schistosome prevalence and mollusk species present in Benin. Malacological analyses revealed the presence of at least five potentially vector mollusk species.
Populations of S. haematobium and S. mansoni were studied through the analysis of life-history traits, including the prepatent period and cercarial production. The study also assessed compatibility between different schistosome populations and mollusk groups. Finally, an anthropic study was conducted in the locality of Toho-Todougba, where both schistosome species coexist, to explore the interactions between parasite life cycles and human activities.
Key Findings
The results of this study indicate that Benin is home to two species of human schistosomes, S. haematobium and S. mansoni, confirming their prevalence in the region. Mixed transmission foci were identified, which complicates the fight against schistosomiasis. Malacologists also discovered several vector mollusk species, including Bulinus forskalii, Bulinus globosus and Bulinus truncatus for S. haematobium, and B. pfeifferi for S. mansoni. In addition, the discovery of Indoplanorbis exustus, an exotic mollusk, marks a first for the country, although it currently appears passive with regard to transmission.
The study of interactions between schistosomes and mollusks revealed that S. haematobium populations show variable compatibility with Bulinus groups. In contrast, all S. mansoni populations are compatible with B. pfeifferi. This finding suggests that control strategies should be targeted according to the specific host-parasite interactions involved.
Analysis of cercarial emission rhythms in S. haematobium and S. mansoni revealed a particular infradian-type hourly cycle. The anthropic study in Toho-Todougba also revealed synergy between human behavior and the dynamics of cercarial emissions, suggesting that schistosomes have developed strategies adapted to coincide with the activities of vertebrate hosts.
Discussion and Outlook
The results of this research highlight the challenges posed by schistosomiasis in Benin and the need for an integrated approach to its control. The high prevalence rates of S. haematobium and S. mansoni, combined with the presence of mixed foci, show that adapted interventions are urgently needed. The variability in compatibility between schistosomes and mollusk vectors indicates that control strategies must be tailored to each region to optimize their effectiveness.
The role of Indoplanorbis exustus, although currently passive, deserves particular attention, as it could become an active vector in the future. Moreover, the observed interactions between schistosome chronobiology and human behavior open up interesting avenues for research. The data collected could guide policymakers in developing prevention and control policies that take ecological and social dynamics into account.
Moudachirou Ibikounle's research provides crucial insights for better understanding schistosomiasis in Benin and lays the groundwork for future studies on strategies to combat these parasites. Further research is needed to explore more deeply the mechanisms of interaction between schistosomes and their hosts, as well as to assess the impact of interventions on the transmission of schistosomiasis in the region.
Key Data
- 85%: Prevalence of S. haematobium in Benin, indicating a high risk of transmission.
- 30%: Prevalence of S. mansoni, highlighting the diversity of schistosomiasis in the region.
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Sources and Access
Moudachirou Ibikounle. Les schistosomoses au Bénin : épidémiologie et écologie des interactions hôte-parasite. Interactions entre organismes. Université de Perpignan Via Domitia; Université d'Abomey-Calavi (Bénin), 2006. Français. ⟨NNT : ⟩. ⟨tel-03412713⟩