Schistosoma mansoni infection suppresses the growth of Plasmodium yoelii parasites in the liver and reduces gametocyte infectivity to mosquitoes.

Taeko Moriyasu,Megumi Inoue,Risa Nakamura,Masato Kubo,Shinjiro Hamano,Masachika Senba,Sharmina Deloer,Richard Culleton,John Pius Dalton

doi:10.1371/journal.pntd.0006197

Abstract

Malaria and schistosomiasis are major parasitic diseases causing morbidity and mortality in the tropics. Epidemiological surveys have revealed coinfection rates of up to 30% among children in Sub-Saharan Africa. To investigate the impact of coinfection of these two parasites on disease epidemiology and pathology, we carried out coinfection studies using Plasmodium yoelii and Schistosoma mansoni in mice. Malaria parasite growth in the liver following sporozoite inoculation is significantly inhibited in mice infected with S. mansoni, so that when low numbers of sporozoites are inoculated, there is a large reduction in the percentage of mice that go on to develop blood stage malaria. Furthermore, gametocyte infectivity is much reduced in mice with S. mansoni infections. These results have profound implications for understanding the interactions between Plasmodium and Schistosoma species, and have implications for the control of malaria in schistosome endemic areas.

Highlights

Malaria and schistosomiasis are two of the most important parasitic diseases in the tropics, and together constitute a severe burden to public health and to the economic development of endemic countries
We evaluated whether S. mansoni infection affects malaria parasite gametocyte infectivity to mosquitoes, as it has been shown that the infectivity of malaria gametocytes decreases during the early stage of malaria infection due to host serum-mediated immunity [25,26,27]
S. mansoni infection significantly reduces the number of malaria parasites in the liver following sporozoite inoculation

Summary

Introduction

Malaria and schistosomiasis are two of the most important parasitic diseases in the tropics, and together constitute a severe burden to public health and to the economic development of endemic countries. Malaria is estimated to cause 429,000 deaths per year, 70% of those occurring in children aged under five years old [1]. The WHO has estimated that schistosomiasis causes about 200,000 deaths every year in sub-Saharan Africa and 218 million people were required to undergo preventive chemotherapy against the helminth globally in 2015. The ranges of Plasmodium and Schistosoma overlap in much of the tropical world, leading to the potential for a great many coinfections of the two parasitic species. It has, for example, been estimated that there may be a greater than 30% coinfection rate among children in SubSaharan Africa [2]. Given the importance of such coinfections, interactions between Plasmodium and Schistosoma have been extensively studied both in nature, and using animal models in the laboratory

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Conclusion