Parasitological and immunopathological responses in mice with concomitant schistosoma mansoni and plasmodium berghei infections

Abstract

Usually, areas endemic for schistosomiasis have malarial infections and vice versa. In Kenya, areas like Mwea, Lake Victoria region, along the coast and Ukambani, are known for this. On the other hand, not much information is available on the consequences of having the two infections together. At the same time, study ofthe coinfections in humans may not allow one to know when the infections started. This study is therefore aimed at investigating parasitological, pathological and immunological responses that occur in mice as models for humans, during a schistosorniasis-malaria co-infection. A group of mice was infected with S. mansoni and then divided into three separate groups. At weeks 4, 5, and 6 post-infection, each separate group was super-infected with P. berghei. There were also uninfected and single-infected controls of both S. mansoni and P. berghei. At various times post-infection with P. berghei, blood samples were taken for assays of parasitaemia and immunoglobulin G (IgG). Liver tissues were also obtained for histopathology, and perfusion done for establishing the worm burden. The procedures were carried out in the experimental mice and their controls. It was found out that mice infected by both parasites developed higher malaria parasitemia, and showed higher IgG responses compared to the single-infected mice. It was also noted that the wormload in the S. mansoni-only-infected group was significantly higher than in the co-infected mice. The granuloma sizes were also larger in the S. mansoni-only-infected groups as compared to the co-infected groups. These results were consistent, regardless of whether-the super-infection was done at week 4, 5, or 6 post- S. mansoni infections, though the difference in worm load at week 4 was not significant. Taken together, the Eata from this study show that schistosome and malaria infections profoundly affect each other. These findings may have implications in the treatment and control of bot~h i.nfections. The results suggest that co-infections with schistosome and malaria parasites would aggravate malaria severity. This would necessitate the need for considering schistosome infection in clinical as well as therapeutic management of malaria patients in areas where the two diseases are co-endemic. On the other hand, the results indicate that malaria confers an advantage to the S. mansoni infection, since the granuloma sizes in co-infected mice were significantly smaller than in the S. mansoni- only infected mice. The worm burden was also significantly higher in the S. mansoni- only infected mice than in the co-infected mice. These findings call for a concerted approach in the control of malaria and schistosomiasis.