Antischistosomal effect of selected plant extracts on swiss white mice infected with schistosoma mansoni

Abstract

Schistosomamansoni is responsible for causing schistosomiasis in humans; a major public health problem worldwide. It is estimated that 200 million people, mostly children are infected with schistosomes. Schistosomiasis occurs in 76 tropical countries, 85% of the infections in Africa. InKenya, it is estimated that 3 million people are infected. Schistosome eggs are responsible for most pathology. Even though conventional drugs are effective in the treatment of the disease, very little progress has been achieved on treatment of schistosomiasis in Kenya. Praziquantel (PZQ) is the most effective drug against all adult stages of human schistosomiasis. Being the only drug used for treatment, other drugs should be sought to avoid development of drug resistance. The use of plant extracts in treatment of diseases is universal. Many plants have been used locally for treatment of bilharziasis in Kenya. The aim of this study was to determine Phytochemistry and antischistosomal activity of five plant extracts, effective dosage and immunological responses of the efficacious extracts, and in vitro assessment of cercaricidal and wormicidal effects. Extracts from the following plants were used: Sonchus luxurians, Ocimum americanum, Bridelia micrantha, Croton megalocarpus and Aloe secundiflora. Plants were collected, identified, dried then extracted using hexane, Dichloromethane/methanol and water. Swisswhite mice were infected, treated with plant extracts and worms recovered. Pathological, immunological, cercaricidal and wormicidal assays were carried out. The results obtained showed that Ocimum americanum hexane (OAH) and Bridelia micrantha (BMW) water extract nadantischistosomal activity. This was indicated by low worm recovery, high worm reduction, andreduced gross pathology with histopathology showing no or few granulomas in the liver tissue, which was similar to PZQ. The effective dosage of efficacious plants was 300mglml whichwas used for OAH and BMW extracts. The two extracts had both cellular and humoral immunity as demonstrated by IFN-y, IL-5 and IgG responses. OAH and BMW were significantly similarto PZQ; however BMW had higher IgG responses. BMW had higher IFN-y responses for bothspleen and lymph node cells. This implied that treatment groups were able to produce the TH-l response which is important for cell mediated immunity. Although both extracts induced production of IL-5 for both lymph node and spleen cells, OAH generated more IL-5. IL-5 is responsible for humoral responses. The plant extracts with the highest cercaricidal effects were Bridelia micrantha, Ocimum americanum and Sonchus luxurians Dichloromethane and Methanol extracts. The two efficacious extract, BMW and OAH exhibited wormicidal effect. In conclusion the two plants extract, Ocimum americanum hexane and Bridelia micrantha water were efficacious as demonstrated by high worm reduction, reduced gross and histopathology, humoral and cellular responses, similar to PZQ. In addition they were very effective in killing adult worms in vitro. Therefore the two plant extracts are possible candidates for drug development.