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Parasite transmission in social interacting hosts: Monogenean epidemics in guppies

PLoS ONE
By: , , , and 
https://doi.org/10.1371/journal.pone.0022634

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Abstract

Background

Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally.

Methodology/Principal Findings

Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling.

Conclusions/Significance

These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density.

Publication type Article
Publication Subtype Journal Article
Title Parasite transmission in social interacting hosts: Monogenean epidemics in guppies
Series title PLoS ONE
DOI 10.1371/journal.pone.0022634
Volume 6
Issue 8
Year Published 2011
Language English
Publisher Public Library of Science
Publisher location San Francisco, CA
Contributing office(s) Western Ecological Research Center
Description e22634, 6 p.
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