Bilharziasis is a parasitic disease caused by platyhelminthes, affecting millions worldwide. Marine invertebrates generally and marine sponges especially are promising organisms for the synthesis of novel bioactive compounds. There is an urgent need to investigate and develop a new and potential antibilharzial agent instead of using synthetic drugs. The extracts of two marine sponges: Negombata magnifica (Nm) and Callyspongia siphonella (Cs) collected from Gulf of Aqaba have been investigated for their effect as anthelmintic agents. Extracts from both types of sponges were obtained by using CH₂Cl_2, C₄H₈O₂ andCHCl₃ solvent_.  Mice were divided into 6 groups; (G1-G3) include infected mice with cercaria and administrated orally for 2 days a dose of one-tenth of LC₅₀ of each extract from Nm (7.85, 11.25 and 10, mg/kg body weight/mouse, respectively); (G4-G6) administrated each extract from Cs (12.32, 13.11 and 14.25mg/kg body weight/mouse, respectively). G7includes infected mice treated with 200 mg/kg body weight praziquantel for 2 days; G₈ is infected mice and not treated (control group). The effects of each extract on the worm recovery and total egg count were determined.
Oral administration of extract to infected mice (G1, G2 and G3) at 9 weeks post treated (WPT), induced a highly significant reduction, in the mean numbers of male and female worms. The males being more affected than females at 9 WPT. Also, treated mice in (G1), (G2) and (G3) showed a significant reduction in the mean number of female worms compared to the infected untreated mice group (G8). The females being more affected than males at 8 WPT. Only (G1), (G2) and (G3), as well as (G7) produced significant decline in the tissues liver and intestine egg counts at 8 WPT.
In conclusion the current data indicated that the investigated sponge extracts can be applied as potential agent to treat bilharziasis. Also, the results provide a basis for exploring extracts from marine sponge as sources for new bioactive agents.