Change in termite communities along a chronosequence of mango tree orchards in the north of Côte d’Ivoire

Termites constitute the major component of the macrofauna of the soil, and influence the structure of the soil, in tropical regions. This study aimed to estimate their assemblages in a chronosequence of mango tree orchards in the north of Côte d’Ivoire and compare them with those in unmanaged savanna. Using a standardized method of rapid biodiversity estimation, termites were collected in seven age classes of mango tree orchards (class 1: <5 years; class 2: 5–9 years; class 3: 10–14 years; class 4: 15–19 years; class 5: 20–24 years; class 6: 25–29 years; class 7: 30 years and over) and compared with termites collected from the savanna. Results show that the species richness was lowest in the young orchards of class 1 (9 species), and increased with the age of the orchards to reach its maximum in the old orchards of class 7 (28 species); these latter were comparable in richness with the savanna (26 species). The Shannon index (H’) and the evenness (E) follow the same trend as the species richness. The orchards of classes 1 and 2 were more dissimilar to the savanna. In contrast, termites were well represented in the savanna and in the old orchard of classes 6 and 7. Rhinotermitinae and Cubitermitinae subfamilies, absent in the young orchards of classes 1 and 2, were very abundant in the old orchards (classes 6 and 7). Overall, the findings of this study show that only the old mango orchards sustain termite diversity that comes close to that of the savanna. In this region, the cessation of agricultural activities in mango orchards favors the reconstitution of termite communities and presumably the restoration of the ecosystem services provided by termites. Thus it would be possible to combine agriculture and the conservation soil biodiversity.     

Effectiveness of school-based preventive chemotherapy strategies for sustaining the control of schistosomiasis in Côte d’Ivoire: Results of a 5-year cluster randomized trial

BackgroundPreventive chemotherapy using praziquantel is the mainstay for schistosomiasis control. However, there is little evidence on what is supposed to be the most effective school-based treatment strategy to sustain morbidity control. The aim of this study was to compare differences in Schistosoma mansoni prevalence and infection intensity between three different schedules of school-based preventive chemotherapy in an area with moderate prevalence of S. mansoni in Côte d’Ivoire.MethodologySeventy-five schools were randomly assigned to one of three intervention arms: (i) annual school-based preventive chemotherapy with praziquantel (40 mg/kg) over four years; (ii) praziquantel treatment only in the first two years, followed by two years whithout treatment; and (iii) praziquantel treatment in years 1 and 3 without treatment in-between. Cross-sectional parasitologic surveys were carried out prior to each round of preventive chemotherapy. The difference in S. mansoni prevalence and infection intensity was assessed by multiple Kato-Katz thick smears, among children aged 9–12 years at the time of each survey. First-grade children, aged 5–8 years who had never received praziquantel, were also tested at baseline and at the end of the study.Principal findingsOverall, 7,410 children aged 9–12 years were examined at baseline and 7,223 at the final survey. The baseline prevalence of S. mansoni was 17.4%, 20.2%, and 25.2% in arms 1, 2, and 3, respectively. In the final year, we observed the lowest prevalence of 10.4% in arm 1, compared to 18.2% in arm 2 and 17.5% in arm 3. The comparison between arms 1 and 2 estimated an odds ratio (OR) of 0.52 but the difference was not statistically significant (95% confidence interval (CI) = 0.23–1.16). Likewise the difference between arms 1 and 3 lacked statistical significance (OR = 0.55, 95% CI = 0.23–1.29). There was no noteworthy difference observed between arms 2 and 3 (OR = 1.06, 95% CI = 0.64–1.75). The lowest S. mansoni fecal egg counts in the final year survey were observed in arm 1 (7.9 eggs per gram of stool (EPG)). However, compared with 11.5 EPG in arm 2 and 15.4 EPG in arm 3, the difference lacked statistical significance. There were 4,812 first-grade children examined at baseline and 4,513 in the final survey. The overall prevalence of S. mansoni in these children slightly decreased in arms 1 (from 4.5% to 3.6%) and 2 (from 4.7% to 4.3%), but increased in arm 3 (from 6.8% to 7.9%). However, there was no significant difference in prevalence and infection intensity observed between study arms.Conclusions/significanceThe three treatment schedules investigated led to a reduction in the prevalence and intensity of S. mansoni infection among children aged 9–12 years. Comparing intervention arms at the end of the study, no statistically significant differences were observed between annual treatement and the other two treatment schedules, neither in reduction of prevalence nor intensity of infection. It is important to combine our results with those of three sister trials conducted simultaneously in other African countries, before final recommendations can be drawn.