When is a parasite a problem?

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Edited by: James E. ByersApril M. Blakeslee, and John P Wares

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Abstract

A parasite’s perceived societal impact depends on the disease it causes and the perception of the affected host species. For instance, doctors and veterinarians have a mission to treat parasites that infect humans or that impact host species that have some utilitarian or aesthetic value for society. Marine scientists have different concerns than doctors. Although the number of parasites that marine scientists should be concerned about may vary, only 13% of parasites and 6% of host–parasite links might be considered “problematic” in a kelp forest food web. With regard to the many threats to marine ecosystems, these percentages suggest that most parasites and infectious diseases are inconsequential. A related issue is the common expectation that parasites and the impacts that they cause are increasing under stress as ocean environments across the globe degrade. Yet, reports of disease have not increased due to human impacts on the marine environment, where the factors that influence parasitism are more complex. Thus, the expectation that marine parasites create problems, and that the diseases they cause are getting worse, is more likely the exception than the rule.

Suggested Citation

Lafferty, K.D., 2026, When is a parasite a problem?, chap. of The ecology and evolution of marine parasites and disease, p. 5-14, https://doi.org/10.1093/9780197790847.003.0002.

Publication type Book chapter
Publication Subtype Book Chapter
Title When is a parasite a problem?
DOI 10.1093/9780197790847.003.0002
Publication Date April 06, 2026
Year Published 2026
Language English
Publisher Oxford Academic
Contributing office(s) Western Ecological Research Center
Description 10 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title The ecology and evolution of marine parasites and disease
First page 5
Last page 14
Additional publication details