Experimental Evaluation of Schistosomiasis-Malaria Co-infection in Mouse Model System

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Addis Ababa University


Mixed parasitic infections are common in many parts of the world. Plasmodium falciparum and Schistosoma mansoni are co-endemic parasitic infections with broad global distribution. However, little is known about how concurrent infections affect the immunity to and/or pathogenesis of each other. Thus, this study was undertaken to examine the parasitological, histopathological and hematological conditions that occur in Schistosoma mansoni-Plasmodium berghei co-infected mice. Mice infected with S. mansoni cercariae were divided into two groups, which were super-infected at weeks 4 and 7 post-infection with P. berghei. Giemsa stained blood specimens, hematoxyline and eosin stained liver and brain tissues were used for the analysis of parasitaemia, liver granuloma and cerebral sequestration of malaria parasites, respectively. In addition to these, hemoglobin level, percentage weight loss, eggs per gram of liver and survivability of P. berghei infected mice were used as parameters for the comparison of co-infected and mono-infected groups. Sampling of hemoglobin and weight measurements were done at days 3, 5, 7, 9 and 11 post-P. berghei infection. Sampling of blood for malaria parasitaemia was done at days 5, 7, 9 and 11 post-P. berghei infection. Independent t-test analysis of the results showed that co-infection of mice with P. berghei, 7 weeks post-S. mansoni infection resulted in significant (P<0.05) increase in malaria parasitaemia, severe loss of hemoglobin and weight, lower number of schistosome eggs per gram of liver, and decrease in granuloma size and number. In addition, reduction of malaria parasite sequestration in the brain with resultant increase in the life span of the infected mice was associated with co-infection. However, there was insignificant difference during co-infection of mice with P. berghei 4 weeks post-S. mansoni infection. The overall interplay between these two infections may be explained immunologically, with malaria infection down-regulating delayed hypersensitivity reaction, which would lead to reduction in granuloma formation around schistosome eggs. Similarly, chronic schistosome infection may modulate host immunopathological responses that would lead to cerebral sequestration. Taken together, the study showed schistosome and malaria co-infections to profoundly affect each other. These findings can have implications in treatment and in the efficacy of vaccines against schistosomiasis and malaria in co-endemic localities. Key words: Co-infection, S. mansoni, P. berghei, Parasitaemia, Hemoglobin, Granuloma, Cerebral sequestration



Co-infection, S. mansoni, P. berghei, Parasitaemia, Hemoglobin, Granuloma, Cerebral sequestration