Global warming is good news - if you're a parasite!

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Global warming may be a fish parasite's best friend, according to a new study.

In the report, to be published in a forthcoming issue of the journal Global Change Biology, Vicki Macnab and Iain Barber of the University of Leicester studied the bird tapeworm (Schistocephalus solidus) infecting Three-spined sticklebacks (Gasterosteus aculeatus) and found that the parasites grew four times faster after eight weeks when experimentally raised at 20°C compared to those raised at 15°C.  

They speculate that this increase in growth rate could be due to either increased food available for parasites, or the reduction in the competency of the host's immune system at higher temperatures.

The authors also found the sticklebacks to grow more slowly at higher temperatures, although this phenomenon has been noted in previous studies, even with uninfected fish.

Coupled with the increased parasite growth rate at higher temperature, though, this suggests that the delicate balance between host and parasite is set to change in favour of the parasite.

More ominously, the authors also found that the fish infected with parasites showed a significant preference for warmer waters, further tipping the scales in favour of the parasite. Therefore, global warming is likely to significantly increase parasite infection and transmission by enhancing rates of parasite growth and development, and by increasing the likelihood of hosts being able to seek out proliferating warmer microhabitats, conclude the authors.

For more information, see the paper: Macnab, V and I Barber (2012) Some (worms) like it hot: fish parasites grow faster in warmer water, and alter host thermal preferences. Global Change Biology doi:10.1111/j.1365-2486.2011.02595.x

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