Behavior and Parasite Transmission Risk

What determines parasite risk for a host? We often focus on factors such as the host’s immune system and the parasite’s ability to find or infect hosts. However, host behavior can determine a large proportion of infection risk. Take the 10-second rule for example. Some people like to say that food that has been on the ground for less than 10 seconds is safe to eat. That may or may not be true, but it is likely a riskier behavior (in terms of possible food contamination) than not eating food that has fallen to the ground. Engaging in such risky behaviors could thus make 10 second rule followers more likely to obtain parasites than people who do not eat food that has touched the ground. Importantly, this logic applies beyond humans and the 10 second rule. Within a species, one might predict that individuals that are more bold would be more likely to obtain parasites. One might predict this assuming that bolder individuals would be more likely to engage in risky behaviors, such as eating obviously bad meat. A recent study analyzing the contribution of host behavior to parasite transmission, for example, discovered that bold behavior (assessed through number of aggressive interactions and a few other measures) predicted Hanta virus infection in deer mice [1]. Specifically, bold deer mice were much more likely to show positive infection status for Hanta virus than shy deer mice. Cool, right? There are a few qualifications to point out here though. A significant percentage of shy mice were infected with Hanta, meaning there are other factors that need to be researched in the Hanta virus-deer mice system. This study did also not illuminate whether bold deer mice are bold because they were infected with Hanta (Hanta made them bold), or whether deer mice are more likely to obtain Hanta if they are bold (deer mice are bold prior to Hanta infection). Lastly, conclusions about the role of behavior in parasite transmission need to be relatively host and parasite specific. In the Hanta virus and deer mice system, for example, aggressive interactions lead to virus transmission because the virus is spread through bodily fluids. Aggressive interactions in which deer mice wound each other thus promote transmission of Hanta virus. However, for parasites that spread through other means, more sedentary or shy individuals could be more beneficial to parasite transmission.
Literature Cited

1.    Dizney, L. and M.D. Dearing, The role of behavioural heterogeneity on infection patterns: implications for pathogen transmission. Anim Behav, 2013. 86(5).