Antischistosomal Effects Of Solanum Incanum And Carica Papaya Crude Extracts On The Parasite Schistosoma Mansoni In Vivo And In Vitro

摘要

In schistosomiasis infection, the disease is managed by exposing the definitive host to a dose of Praziquantel. However, Praziquantelis still not reaching the majority of those who most need it due to its high cost and there is possibility of drug resistance, hence need for alternatives. Antischistosomal effects of crude Solanum incanum and Carica papaya extacts were studied. Patterns on immune response, worm recovery, gross pathology in vivo and cercaricidal killing in vitro of Schistosoma mansoni was observed. In vivo S. mansoni infections were treated with two doses of 150 mg/kg of Solanum incanum or Carica papaya (methanol or aqueous) extracts and a treatment control of 450 mg/kg of Praziquantel. Various concentrations of plant extracts were used in cercaricidal assay. Carica papaya, showed highly reduced pathology, elevated immune responses and least time in destroying cercariae. On the other hand, S. incanum had the highest reduction in worm counts, similar to Praziquantel. Further studies are required to isolate the active compound(s) and determine mechanism(s) of their action. Introduction Schistosomiasis is a major disease of public health in humans, occurring in over 74 countries of the tropics and sub-tropics (WHO, 2010). It affects an estimated 207 million or more individuals and cause an estimated 500,000 deaths every year. Its current increased prevalence in many areas has numerous causes, including increased irrigation in areas with inadequate waste disposal and breakdown in public health infrastructure. The most common significant clinical effects of infection are intestinal and hepatic manifestations, which can result in serious illness or death (David et al., 2006). In Kenya, the infection is wide spread around Mwea irrigation scheme in Kirinyaga district, Machakos, Kitui, Taita Taveta and Nyanza (WHO, 2006).The possible existence of S. mansoni isolate tolerance to Praziquantel has been reported in Senegal where the parasitological cure rate 12 weeks after treatment was as low as 18% (Berquist, et al., 2002). In regions of Egypt and Kenya where there has been heavy exposure to Praziquantel, there are reports of S. mansoni and S. haematobium resistance to treatment (Ross et al., 2002). This has necessitated the search for alternatives to praziquantel and other tools for control of schistosomiasis.Plants are frequently discussed as possible sources of novel drugs, and in recent years they have been investigated as potential sources of antiparasitic agents including novel antischistosomal agents (Sher, 2001; Hagan et al., 2004). Crushed seeds of the plant Nigella sativa (Rununculaceae) were found to have antischistosomal activity against different stages (cercariae and juvenile) of S. mansoni (Mohamed et al., 2005). Artemisinin derivatives, now seen as important antimalarials, have been shown to have an effect on schistosomes. In China, artemether has been used successfully for acute S. japonicum infections in times of flood (Xiao et al., 2000). In this study, S. incanum and C. papaya methanol and aqueous extracts were assayed in vivo and in vitro for antischistosomal activities. Methodology Herbal Extracts Solanum incanum roots and Carica papaya seeds were collected and placed in plastic bags. The plants were dried at room temperature for 2 months and crushed into tiny particles using Mekon Micromealer Single Phase and passed through a 0.5 mm mesh to standardize the particles. The ground plant material for each plant was divided into two equal portions and separately placed in two clean large bottles. Distilled water was added to one bottle holding each plant type until the sample was slightly submerged, after which it was left to soak for 72 h. The content was filtered; the process of soaking and filtering was repeated 3 times. The three filtrates were mixed in a container and freeze-dried using a freeze-drying machine (model FD-A made in Japan) for a month after which the aqueous extract was obtained in powde