Unearthing roundworms: Nematodes as determinants of human health

Abstract

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.

Keywords: Education; Human health; Model organisms; Nematodes.

Fig. 1

The direct and indirect effects of nematodes on human health. Clockwise description of the circles, starting on the top-left: 1) Plant-parasitic nematodes such as Globodera and Meloidogyne infect virtually all of the crops humans rely on for food. 2) In natural ecosystems, nematodes cover many trophic levels, from bacterivorous or fungivorous to predatory (as the depicted Pristionchus). 3) Nematodes, especially Caenorhabditis elegans, have been extensively used as research model and have driven many advances in the field of biology. Nematodes are also great for use in teaching, and can be used to illustrate some biological concepts for children at primary school level. 4) Animals can be infected by nematodes, and grazing ruminants (like sheep) especially suffer from gastrointestinal worms. 5) Humans can be infected by a diverse range of nematodes, including (the now almost eradicated) Dracunculus medinensis. 6) Nematodes can also parasitize invertebrates (like insects) and some of these are applied in biocontrol, like Steinernema.