VIEWPOINTS It’s All about Those Bases: The Need for Incorporating Parasite Genetic Heterogeneity into the Development of Schistosome

Parasite genetic variation has been used to delineate and enumerate species, describe host–par-asite associations, and observe the distribution of lineages among hosts and throughout the en-vironment. Mechanisms or pathways inferred by these studies have often been carried forward in a predictive manner to inform assumptions about the organism’s biology, its life history, and host–parasite interactions. For medically relevant parasites, these observations have undoubt-edly proven useful for a fuller epidemiological understanding of parasite transmission path-ways and patterns. Here, we argue that functional parasite genetic variation in natural populations of schistosomes is poorly understood and that a better understanding of this varia-tion is crucial to the development of effective vaccines. Parasites in the genus Schistosoma are responsible for causing the disease schistosomiasis, a neglected tropical disease that affects over 200 million people in 74 countries [1]. Despite con-siderable effort and exploration, an effective human vaccine for this disease remains elusive [1]. An increasing array of studies assessing genetic variation within the medically relevant species of Schistosoma has indicated that old paradigms of focal transmission patterns and subsequent-ly restricted parasite gene flow do not always hold up against genetic evidence (e.g., [2,3])