Case Report: Diagnosis and Assessment of Cure Approaches for Acute Schistosomiasis in Pre-School Children

New challenges for the control of human schistosomiasis: The possible impact of wild rodents in Schistosoma mansoni transmission

Schistosomiasis is a neglected parasitic disease caused by digenean trematodes from the genus Schistosoma that affects millions of people worldwide. Despite efforts to control its transmission, this disease remains active within several endemic regions of Africa, Asia, and the Americas. In addition to the deficits in sanitation and educational structure, another major obstacle hindering the eradication of schistosomiasis is the ability of Schistosoma spp. to naturally infect multiple vertebrate hosts, particularly wild rodents. Due to climate change and other anthropogenic disturbances, contact between humans and wild animals has increased, and this has contributed to more frequent interactions between Schistosoma species that typically infect different hosts. This new transmission dynamic involving Schistosoma spp., humans, wild rodents, and livestock could potentially increase the frequency of Schistosoma hybridization and the establishment of new genotypes and strains. Although it is not currently possible to precisely measure how this biological phenomenon affects the epidemiology and morbidity of schistosomiasis, we speculate that these Schistosoma variants may negatively impact control strategies, treatment regimens, and disease burden in humans. In the present study, we discuss the natural infections of wild rodents with Schistosoma spp., the role of these animals as Schistosoma spp. reservoirs, and how they may select hybrids and strains of Schistosoma mansoni. We also discuss measures required to shed light on the actual role of the wild rodents Nectomys squamipes and Holochilus sciureus in the transmission and morbidity of schistosomiasis in Brazil.

The Road to Elimination: Current State of Schistosomiasis Research and Progress Towards the End Game

The new WHO Roadmap for Neglected Tropical Diseases targets the global elimination of schistosomiasis as a public health problem. To date, control strategies have focused on effective diagnostics, mass drug administration, complementary and integrative public health interventions. Non-mammalian intermediate hosts and other vertebrates promote transmission of schistosomiasis and have been utilized as experimental model systems. Experimental animal models that recapitulate schistosomiasis immunology, disease progression, and pathology observed in humans are important in testing and validation of control interventions. We discuss the pivotal value of these models in contributing to elimination of schistosomiasis. Treatment of schistosomiasis relies heavily on mass drug administration of praziquantel whose efficacy is comprised due to re-infections and experimental systems have revealed the inability to kill juvenile schistosomes. In terms of diagnosis, nonhuman primate models have demonstrated the low sensitivity of the gold standard Kato Katz smear technique. Antibody assays are valuable tools for evaluating efficacy of candidate vaccines, and sera from graded infection experiments are useful for evaluating diagnostic sensitivity of different targets. Lastly, the presence of Schistosomes can compromise the efficacy of vaccines to other infectious diseases and its elimination will benefit control programs of the other diseases. As the focus moves towards schistosomiasis elimination, it will be critical to integrate treatment, diagnostics, novel research tools such as sequencing, improved understanding of disease pathogenesis and utilization of experimental models to assist with evaluating performance of new approaches.