Parasitology at the heart of the "One Health" concept: a longstanding alliance illustrated by cysticercosis control.

The "One Health" concept, emphasizing the interdependence of human, animal, and ecosystem health, has gained renewed global attention and institutional support from the World Health Organization, Food and Agriculture Organization of the United Nations, United Nations Environment Program, and World Organization for Animal Health. Here we underline that some principles of parasitology are embedded in this concept. As early as the 19th century, Rudolf Virchow affirmed the unity of human and veterinary medicine, a vision long practiced by parasitologists through their multidisciplinary work on zoonotic diseases. The classical "One Health" triad (humans, animals, and ecosystems) closely mirrors the complex life cycles of many parasitic zoonoses, where distinct stages circulate among hosts and ecosystems. Parasitology societies worldwide have fostered collaboration among scientists, veterinarians, physicians, and other professionals, embodying some aspects of the "One Health" approach well before its formal recognition. Using cysticercosis as an example, this article illustrates how a multisectoral, integrated framework could support effective disease control. We argue that implementing a comprehensive "One Health" strategy to combat parasitic diseases requires a systemic approach that encompasses not only veterinary and human medicine, but also ecology, the social sciences, and economics. This approach must explicitly consider research objectives related not only to human and animal health, but also to ecosystem health.