The effect of one versus two Praziquantel treatments on Schistosoma Monsoni morbidity and re-infection along Lake Victoria in Uganda

Abstract

Schistosomiasis is a debilitating disease and the most widespread water-borne parasitic disease. It affects approximately 4 million people in Uganda and 13% of the population are at risk of infection. Schistosomiasis control target is to reduce morbidity. In Uganda, a national control program for Schistosomiasis and other intestinal worms was launched in 2003. Since then, affected communities have been undergoing mass treatment using a single standard dose (40mg/kg body weight) of praziquantel taken once a year. However, schistosomiasis is still prevalent along large water bodies. More information is required to find out whether different chemotherapeutic regimens of praziquantel would combat the levels of schistosomiasis infection. To fill this information gap, a longitudinal randomised intervention study was carried out to compare the effect of two doses versus one dose of praziquantel on schistosomiasis infection and related morbidity. The aim of this study was to enhance our knowledge about the use of different praziquantel treatment regimens in the control of schistosomiasis.

The study was conducted in Musoli village along Lake Victoria, Eastern Uganda. A cohort of 446 people was followed over a period of 2 years. Pre-treatment S. mansoni infection and related morbidity data, and water contact patterns were obtained. All participants were given a single dose of praziquantel after which they were randomised to two groups. Two weeks later, one of the groups received a second dose of praziquantel while the other group was not given any other treatment. Follow up surveys were performed nine weeks, eight and 24 months after treatment. Analysis was performed using ANOVA, student`s t test, paired t test, pairwise correlation and chi-square test using Stata for windows (Intercooled Stata 10.1, Stata Corporation, USA). A P value <0.05 was used to determine statistical significance.

The S. mansoni infection prevalence and the geometric mean intensity (GMI) were 88.6% (95% confindence interval [95% CI]: 85.6 – 91.5) and 236.2 (95% CI: 198.5 – 460.9) eggs per gram of faeces respectively. The prevalence of splenomegaly, hepatomegaly and hepatosplenomegaly were 4.9%, 24.2% and 30.3% respectively. Periportal fibrosis was minimal. Cure rates of single and double dose treatment groups were 47.9% and 69.7% respectively, significantly different (Relative risk = 1.7, 95% CI = 1.3 – 2.2). The egg reduction rate of a single dose (92.3%) was not significantly different from that of two doses (93.9%). Occurrence of re-infection was not significantly different between the two treatment groups. There was no significant difference in growth parameters and prevalence of anaemia between the two treatment groups. The prevalence of splenomegaly and hepatomegaly were not significantly different between the two treatment groups. However, 24 months after treatment, prevalence of hepatosplenomegaly showed a significant difference between the two treatment groups (95% CI: 14.1 – 24.5 for single dose and 95% CI: 4.6 – 13.0 for two doses).

In conclusion, Musoli village is highly endemic for schistosomiasis. Two doses of praziquantel are not superior to a single dose with regard to reducing schistosomiasis reinfection and related morbidity. This study therefore supports the current treatment strategy of a single annual dose of praziquantel in the control of schistosomiasis infection. Nonetheless, schistosome parasites can develop resistance to praziquantel especially in control programmes. Therefore there should be mechanisms to monitor parasite tolerance to praziquantel and control of schistosomiasis should be integrated with other preventive measures.