Choosy parasites pick hosts by sex

CORNELL (US) — Some parasites favor hosts of one sex over the other, possibly because of sex-specific immune responses or behavior.

A Cornell University postdoctoral researcher in entomology proposes that such differences as morphology, physiology, behavior, diet, and life history traits between the sexes in the host species can, in fact, pose very different challenges and opportunities to their parasites, causing them to adapt to one host sex.


Sex-specific adaptations in parasites may also occur when parasites routinely encounter one host sex more frequently than another. Parasites adapted to male or female hosts may help explain sex differences in parasite prevalence and disease expression.

The “ideas” paper, which proposes the hypothesis, is published in the journal PLoS Biology.

“Our hypothesis may help explain the widespread phenomenon of host sex-biased parasitism and disease expression,” says David Duneau, the lead author of the paper. “We suggest a new perspective on host-parasite interactions, taking parasite evolution into account.”

The paper outlines different scenarios in parasite evolution that can lead to sex-specific disease. These include “sex-specific adaptations” with subpopulations of the parasites either adapted to females or males and “single sex specialization” with the parasite specifically adapted to one host sex.

The final scenario is “plastic sex-specific disease expression” with the parasite adapted to respond one way to male hosts and another way to female hosts.

Further research may help explain questions from many varied fields, such as why effects of vaccines can be sex-specific; how parasites among hosts and at large are distributed; and why parasites can be locally adapted to certain host sexes.

Duneau wrote the paper, supported by the Swiss National Science Foundation, while he was a graduate student at the University of Basel, Switzerland.

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