Assessment of Impact of Repeated Annual Mass Drug Admistration of Praziquantel On Schistosomiasis Morbidity in School Children in Asembo Bay, Western Kenya

Abstract

Schistosomiasis remains a major public health problem in Kenya. The World Health Organization (WHO) recommends preventive chemotherapy with praziquantel (PZQ) through mass drug administration (MDA) to school age children to control morbidity due to schistosomiasis. Morbidity is considered linked to intensity of infection, which along with prevalence is used to determine the frequency of mass drug administration (MDA) to school-age children. Previous studies typically compared children who were uninfected after receiving MDA to their condition prior to treatment. This study hypothesized that multiple MDAs would result in decrease of worm burden and thus egg intensity and prevalence and in addition provide benefits such as decreased morbidity even if the children remained infected. The specific objectives were to determine schistosomiasis grade-intensity before and after successive rounds of annual MDA with PZQ, to assess morbidity measurements before and after successive rounds of annual MDA with PZQ and to determine if the measurements associated with morbidity change upon multiple rounds of annual MDA with PZQ. This study used a repeated cross-sectional study design to determine the impact of annual school-based MDA on children across all primary and high school years in five schools in Asembo Bay region near Lake Victoria in western Kenya, an area endemic for S.mansoni. At baseline and for the following four consecutive years, 897 and 1,440 school-going children in grades 1-12 were enrolled and stool samples evaluated by Kato-Katz for S. mansoni and soil transmitted helminths (STHs), blood samples for malaria diagnosis and anemia evaluation followed by annual MDA with PZQ and albendazole (ALB). For morbidity, to evaluate potential changes in morbidity, height, weight, mid-upper arm circumference, hemoglobin levels, abdominal ultrasound, and quality of life in children in these schools were measured. Morbidity component compared two cross-sectional samples of Schistosoma mansoni egg-positive children: one at baseline and one at year five, after four rounds of MDA. Data were analyzed for all ages (6-18 years old) and stratified by primary (6-12 years old) and secondary (13-18 years old) school groups. Four annual rounds of MDA with PZQ were associated with reduced S. mansoni prevalence in all school children (44.7–14.0%; P<0.001) and mean intensity of infection by 91% (90.4 to 8.1 eggs per gram [epg] of stool; P < 0.001). Prevalence of high-intensity infection (≥400 epg) decreased from 6.8% at baseline to 0.3% by the end of the study. A Chi square test for trend (CochranArmitage) was used to evaluate the association between annual treatments and changes in prevalence of S. mansoni and STH. Soil-transmitted helminth infections, already low (22.4%) at baseline, also decreased significantly (22.4%–10.1%; P=0.029) over the years. The prevalence of multiple potential morbidity markers did not differ significantly between the egg-positive participants at baseline and those at five years (13-18 years old–PedsQol-Physical; P=0.599, PedsQol-Emotional; P=0.218, PedsQol-Social; P=0.821, PedsQol-School; PedsQol-Total; P=0.344 and for organomegaly; 6-12 years old– Hepatosplenomegaly; P=0.831; Stunting; P=0.585 and wasting P=0.999; 13-18 years old– Hepatosplenomegaly; P=0.463; Stunting; P=0.683 and wasting; P=0.077) by Mann Whitney U nonparametric analysis and Fisher’s exact test for continuous and categorical data, respectively. However, in all 13-18 years old and malaria negative 13-18 years old, there were significantly higher scores in school-related quality of life assessment by year five compared to baseline by Mann Whitney analysis (P=0.021* and P= 0.048*) respectively. Anemia registered a significant negative outcome and was not impacted positively by four rounds of MDA. In conclusion, annual school-based MDA with high coverage across all Grades (1–12) resulted in rapid and progressive declines in overall prevalence and intensity of infection in this high endemic area. This decrease was dramatic in regard to heavy infections in older school-attending children. For morbidity, there were no differences in the morbidity markers measured in a population of those infected or re-infected after multiple MDAs with praziquantel. These results are useful in informing policy on inclusion of high school children in MDA in schistosomiasis endemic areas. Further research is needed to identify and develop well-defined, easily quantifiable S. mansoni morbidity markers for this age group.

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