Unearthing roundworms: Nematodes as determinants of human health.

Nematodes are all around us, both in the environment and associated to all imaginable organisms, ranging from plants to animals and humans. As such, nematodes are intimately linked to human, animal and plant health, both directly and indirectly, positively and negatively. Historically, studies mainly focused on the direct negative impact nematodes induce. As a result, we lack a comprehensive overview on the importance of nematodes - including non-direct and positive links. Therefore, we holistically report how human health is affected by direct interactions with nematodes, and indirect interactions via plants, animals and the environment. For that, we first focus on nematodes as human pests, but also show that some of these human-associated nematodes can positively affect human immunity. Subsequently, we summarize how nematodes impair food production and the environment as animal and plant pests, followed by an overview of the multiple indirect links that often benefit human health by enhancing animal and plant performance. Finally, we highlight the different opportunities to improve human health with nematodes, emerging from nematodes as model organisms, as a source for immunomodulatory proteins and as biological products in agriculture. We believe that our review will foster studies on links between nematodes and human health that we believe are highly promising to advance science and technology.