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Pathogens find new hosts as Arctic ice melts

By Julie Cook - 01 Mar 2014 7:20:1 GMT
Pathogens find new hosts as Arctic ice melts

Belugas troubled by the common cat parasite? The Arctic ice has held back a flow of pathogens for thousands of years. Now we may have to suffer further consequences of global warming; Beluga image. Credit: © NOAA

A well-documented effect and concern stemming from climate change is that of melting Arctic ice. Environmentalists have long lamented over the potential of rising sea levels and water temperature as well as the reduced sunlight reflection that the ice provides. Unfortunately, another concern can now be added to this list: that of increased parasites in marine mammals.

The Arctic ice serves many regulatory functions but one that often goes unnoticed is as a barrier to various parasites. In a recent study, beluga whales have now been observed as carriers of the infamous cat parasite Toxoplasma gondii, also known as the kitty litter disease. This is a concern not only for the health of the whale population, but also that of the Inuit people. As one of the authors of the study, Stephen Raverty, notes, the gravity of this situation is that this is now a risk to their food safety as well as to their culture which is based heavily on the belugas.

These findings were presented at the 2014 Annual Meeting of the American Association of the Advancement of Science by Steven Raverty (a veterinary pathologist) and Michael Grigg (a molecular parasitologist), and were met with alarm from the ecological community. They mention that they are currently unsure just how the parasite made the leap to the whales, but they do recognize that the lack of ice was a contributing factor. Toxoplasma gondii is a particularly resistant pathogen, able to withstand even bleach but is often killed by either boiling or freezing water. As the frozen ice retreats, Toxoplasma can now expand to new warm-blooded hosts.

Sadly, this is not the only pathogen-marine mammal relationship that has developed due to the melting Arctic ice. Gray seals have recently been dying off by the hundreds as a result of the Sarcocystis pinnipedi parasite which wreaks havoc on the livers of these seals.

This is a parasite that is already found in some species of seal like the ring seal. This seal species depends on the ice for rearing their young, and therefore live at higher latitudes than the grey seals but appear to be relatively unaffected by the parasite. Thus, in a move opposite of the Toxoplasma parasite, Sarcocystis is moving from North to South as the habitats of the seals now overlap due to the decrease in ice. Previously, this was not an issue as grey seals had restricted contact with ring seals because of the ecological barrier of the ice.

This discovery when coupled with the loss of ice habitat for marine mammals is a serious ecological concern. Many of these mammals are keystone species, their positions near the top of the food chain maintaining the balance of all the species below them. While the observation of these parasites brings to light the wonderful intricacy and complexity of the ecological system, it also highlights the need for preservation and reconsideration of our current environmental trajectory.

There's more on this AAAS. news in Chicago from Steven Raverty and Michael Grigg with an introduction from Carla Schaffer.