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.     

Comparative Study between CalTOX and Soil Screening Levels Modeling Approaches

A comparison was made between two different approaches to environmental modeling and risk assessment, specifically the one-medium approach of the USEPA Soil Screening Levels (SSL) and the multimedia approach in the CalEPA (CalTOX). Eleven priority pollutants were selected to represent different classes of chemicals as per their toxicity, physical and chemical properties, and persistence in the environment. Benzene, dioxin, PCB, B(a)P, chlo-rdane, chloroform, and TCE represent carcinogens, while xylene, toluene, phenol, chlordane, pyrene, TCE, and chloroform represent noncarcinogens. The highly volatile contaminants, including benzene, chloroform, xylene, toluene, and TCE, were selected to compare the volatilization from soil and the significance of inhalation pathways of the two models. The contaminants with strong sorption to soil and dust particles (dioxin, B(a)P, PCB, and chlordane) exhibited a preferential soil ingestion pathway. In contrast with CalTOX, inhalation was not considered as the dominant pathway for all the volatile contaminants in SSL. Furthermore, the risk assessment component of CalTOX accounts for multiple pathways as a consequence of its multimedia representation. Because the two models were based on different approaches, it is expected that the results would be different. For example, the results of the SSL were more conservative compared with CalTOX for all 11 chemicals. This observation still holds when considering the total risk from CalTOX vs. the risk based on the dominant pathway in SSL. Finally, the cancer slope factors and references doses were not the same for all the chemicals used in this study and resulted in different risk estimates.     

Health problems of windowless henhouses

The working, health and zoohygiene problems of keeping chickens (45,000) in TEROZ type windowless houses on deep litter with controlled light regimen and hens (75,000) in cages were the subject of study for 3 years. The poultry was fed on factory-produced feedstuffs with the then permitted addition of CTC in amounts of 20 g/l tonne. Except for the low intensity of illumination in the chicken house (10-1.1 1x) and with the observation of the prescribed technology, the working environment is favourable. The state of health of the employees did not differ essentially from that of other groups of workers in aggriculture. The use of CTC resulted in a growing number of resistant microbial strains (Staphylococcus aureus, Proteus mirabilis, E. coli, etc) which led to the banning of its use and replacement by other biostimulants. Every type of large-scale poultry farm should be designed as a whole including the chicken incubator, the egg sorting station, the slaughter house, the use of waste matter and sewage disposal and should be previously tried out experimentally by a group of experts concerned with the given problems, before being introduced into wider use.