Wormholes in Host Defense: How Helminths Manipulate Host Tissues to Survive and Reproduce

Over 1,000,000,000 people and innumerable other animals are currently infected with one or more helminths [1]. These highly prevalent infections contribute to significant illness and economic losses due to impaired worker productivity and livestock health. As such, it is tremendously important to vaccine and anthelminthic drug development efforts to understand the complex interactions between host and parasite, including helminth manipulation of host tissues. The extensive coevolution of helminths and their hosts often blurs the line between what is host-mediated and what is parasite-driven. However, we have drawn explicit examples from the literature to highlight five major themes of helminth manipulation of host tissues: disruption of epithelial barriers, reinforcement of epithelial barriers, alteration of lymphoid tissue, modulation of tissue vascularity, and tuning of granulomatous responses. Herein we focus on examples of direct molecular level effects on host tissue to highlight strategies common to numerous helminths in their efforts to survive and reproduce within their hosts.