**1. Introduction**

The World Health Organization (WHO) considers schistosomiasis the most important water-based disease in the world. The disease is caused by infection with trematodes of the genus *Schistosoma* species. These parasitic worms have a complicated life cycle (**Figure 1**). When an egg is passed in the feces or urine, it contains a fully developed miracidium. In freshwater, eggs hatch to miracidia, which swims in the water to find a suitable snail host. Upon finding a host, they penetrate its skin. The

**Figure 1.** *The life cycle of the most important human* Schistosoma *in Africa.*

miracidia then transform into primary-stage sporocysts and migrate to the liver of the snail, where they start asexual reproduction to produce daughter sporocysts. The daughter sporocysts develop into cercariae, which are shed into the water. Then the cercariae swim until they find a susceptible vertebrate host, and penetrate its skin. Once the fluke is inside, it drops its tail, and becomes a schistomulae; upon reaching a blood vessel, the schistomulae enters and starts its journey to the lungs, becoming longer and slenderer and losing its middle spines but retaining its end spines. The parasite reaches the lungs six to eight days after infection and begins to feed. The fluke leaves the lungs through pulmonary veins to the liver. By week four, the adult fluke emerges, and it starts pairing about week five. The paired flukes migrate from the portal vein to the respective blood vessels and start to lay eggs. Using their spines, the eggs penetrate through blood vessels to the intestine or urinary bladder [1, 2].

The damage caused by schistosomiasis results from the movement of eggs through host tissue, which triggers an inflammatory response and acute, chronic disease. Schistosomes (as members of the genus *Schistosoma* (*S.*) are commonly known) have an average lifespan of 3 to 10 years, but can live up to 40 years in their vertebrate hosts [3].

Due to increased human population growth, anthropogenic environmental changes, and global movements of humans and animals, there are increasing reports of hybridization events among *Schistosoma* species across Africa. Since these events involve species that infect both humans and animals (domestic and wild), researchers have raised concerns about the emergence of potential schistosomiasis zoonosis [4]. This chapter

Schistosoma *Hybridizations and Risk of Emerging Zoonosis in Africa: Time to Think of a One… DOI: http://dx.doi.org/10.5772/intechopen.103680*

explains how the anthropocentric or disjointed sectoral approach to controlling human schistosomiasis requires a paradigm shift that entails a multisectoral (i.e., One Health) approach to preventing zoonotic transmission of schistosomiasis in Africa.
