Four groups of female C57BL/6 mice were used. The first group was infected with 500 unattenuated cercariae. The second group was immunosuppressed by cyclophosphamide (Cy) before infection with the same dose of cercariae. The third group was exposed to 500 partially attenuated cercariae while the fourth group was immunosuppressed with (Cy) before exposure to 500 partially attenuated cercariae. In response to infection with either unattenuated or partially attenuated cercariae, the total worm burden was significantly reduced. In the meantime, the level of serum specific anti-SWAP IgG1 was significantly higher and a specific band at 32 kDa was recognized in the infected groups (first and third) compared to that in the immunosuppressed groups (second and fourth). Scanning electron microscopy observations revealed severe damage and deformities on the tegument of worms of the third group compared to less damage detected on the tegument of worms in the fourth group. No obvious changes could be detected on the tegument of worms developed from the second group compared to the first group (controls). These observations taken together indicate that the high level of anti-SWAP IgG1 may have a role in the elimination of schistosomes after primary infection of mice with either unattenuated or partially attenuated S. mansoni cercariae. Moreover, this immunoglobulin together with UV-induced attenuation produce severe damage on the tegument of worms developed from mice exposed to partially attenuated cercariae.