Monday, February 28, 2011

Paper: Who Spreads Parasites in Lizards?

Little is known about how parasites are spread through in host populations. Spread patterns should depend on host contact patterns. Social network analysis provides great tools for modeling parasite and pathogen transmission in host populations. Theoretically, highly connected individuals are in greater risk of being infected.

In a recent paper in the Journal of Animal Ecology, Fenner et al. describe the infection patterns of a tick and a nematode in the pygmy bluetongue lizard (Tiliqua adelaidensis), a solitary lizard from South Australia. These lizards don't move much, staying in burrows most of the time.
A relative: the blotched bluetongue lizard
The authors used 3 plots representing sub-populations in the same area. In the only plot in which ticks were found on lizards, lizards that had more or closer neighbors, i.e. more connected, had more ticks. Stable resident hosts were more important than dispersers in influencing tick distribution.

For nematodes there was support for the role of dispersers - infected hosts were more connected to dispersers. This suggests there are different transmission pathways for different parasites, possibly due to differences in parasites survival times.

To summarize, this paper shows the strength of network analysis in exploring alternative hypotheses about the dynamics of infection patterns. It also exposes once again the dependence of the result on the way the network was defined - in this case the distances between burrows of lizards.

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