Cytokine (IL-5, IL-10, IL-13 AND IFN-γ) Profiles Of School Children Infected By Schistosoma Mansoni Upon Multiple Treatments With Praziquantel

ABSTRACT

Schistosomiasis is a parasitic disease caused by trematode worms. The most prevalent species of the worm in Kenya is Schistosoma mansoni. The disease is endemic in parts of Nyanza, Eastern and Coast provinces. Its prevalence in primary school children in Asembo area near Lake Victoria in Rarieda district of Nyanza province is about 17%. Children are more susceptible to infection than adults and thus bear a greater burden of schistosomiasis in terms of morbidity and intensity of infection. Cytokines are an important parameter which can be used to evaluate an individual‟s immune responses and as an indicator of susceptibility, resistance and morbidity to the disease. This study sought to determine progressive cytokine profiles of a cohort of Schistosomiasis mansoni infected school children upon single or multiple treatments with Praziquantel. The children were recruited into two separate groups of about 90 children each. One group designated arm A were diagnosed, specimens collected and treated where necessary, 3 times a year, once in each term of the school year. The other group, designated arm B was diagnosed, specimens collected and treated at time zero and after 24 months. Infection intensity was based on eggs per gram of faeces. Cytokine responses from whole blood cultured with soluble egg antigens (SEA) and soluble worm antigen preparation (SWAP) were determined by ELISA. The cytokines assayed were IFN-γ, IL-5, IL-10 and IL-13. The relationship between cytokine production and infection intensity was determined by correlation test. The effect of multiple treatments on cytokine levels was also determined and comparisons made between cytokine levels of children treated once and those treated multiple times. Infection intensity in the children ranged from a minimum of 12 to a maximum of 2088 epg of faeces and a mean of 217.8 epg of faeces. At the end of the study following single or multiple treatment, infection intensity had dropped, ranging from 0 to a maximum of 828 and mean of 43.22 epg of faeces. Out of a total of 113 children who remained in the study, 36 were not re-infected, 10 in the multiple treatment group and 26 in the single treatment group at the end of the study. No significant correlations were obtained between cytokine levels and infection intensity except for IL-13 (P0.05). There were also no significant differences in cytokine levels between children treated once (arm B) and those treated multiple times (arm A). Based on the findings of this study, it is recommended that other immunological parameters such antibody and B cell responses be used to assess possible immunity development in children following repeated treatment after reinfection in children. For control of schistosomiasis, a combination of strategies should be adopted besides treatment, including public education, improved sanitation and provision of clean drinking water. Finally, a follow-up period for retreatment of reinfected children should be more than three months but less than 2 years to realise meaningful gains in the control of schistosomiasis. More research should however be done to determine the most appropriate follow-up treatment time. Studies should also be done to elucidate other immunological responses elicited in children who undergo repeated treatment after reinfection.