On Earth Day, Remember Parasites


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The California condor was returned to the wild without its parasites. Image courtesy of the US Fish and Wildlife Service

We Should Be Worried About Parasites

We hear about the sixth mass extinction – we’re losing species steadily. Surprise: most of the species we’re losing are probably invertebrate parasites.

According to Dunn et al, “extinction of just five North American carnivore species, for example, is predicted to lead to 56 parasite extinctions from carnivores.

If we lose a host, we lose all parasites that need that host for survival. In spite of this, the authors note that “just one parasite species is listed in the IUCN Red List as endangered because of the rarity of its host, the pygmy hog-sucking louse.. known only from the world’s smallest (and rarest) pig.”

Surprisingly, we’re only beginning to understand what our lack of attention to parasite extinction could mean. In fact, efforts to save endangered species such as the California condor have typically involved systematic removal of parasites.

In the case of the condor, extinct in the wild before reintroduction, this presumably means that all of its specialist parasites are gone for ever. Dunn and colleagues wonder “whether the few remaining California condors… are really bereft of parasites or whether those host-specific parasites have been replaced by generalists, with equal or greater health impacts.”

A Plea for Parasites

There’s no question that parasites have poor PR, but does it really make sense to despise organisms that are so integral to life on Earth? On Earth Day, remember, it takes all kinds to make a world, and our world just wouldn’t be the same without its myriad parasitic species.


Dunn R, Harris N et al. The sixth mass coextinction: are most endangered species parasites and mutualists? (2009) Proceedings of the Royal Society B. 276(1670): 3037–3045.

Gomez, A, Nichols E et al. Parasites, Conservation Medicine and Ecosystem Health. (2012) In: New Directions in Conservation Medicine: Applied cases of Ecological Health. Aguirre A, Ostfeld R. et al, Eds. Oxford University Press. Ch 4.

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