Map shows distribution of parasitic worms

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Parasitologists have created a map that not everyone will want to see; a map of marine parasitic worms which cause gastrointestinal diseases.

The worms from the genus Anisakis have a complex lifecycle ending with Baleen and toothed whales. Each year around 20,000 people are infected by these nematodes and suffer from illnesses ranging from gastrointestinal diseases to serious allergic reactions as a result.

A team led by Prof. Dr. Sven Klimpel, head of the project group on medical biodiversity and parasitology at the Biodiversity and Climate Research Centre (BiK-F) in Germany, combined data from 53 publications with the results of some molecular-biological analyses to create a distribution map of Anisakis species in various oceans around the world. The resulting maps, like the one below, not only enable statements to be made on the occurrence and migration behaviour of some of the hosts such as whales, but also provide conclusions on the risk of human infection.

"By means of our molecular analyses and the model based upon them we can draw detailed conclusions about the occurrence of whale species in very specific areas and thus make statements with regard to the size of their population and stock," says Klimpel.

Before reaching the whale the parasite travels through fish, squid and crabs. If an infected animal is eaten, humans can become infected leading to ‘anisakiasis’. This illness is becoming increasingly common and often occurs in regions in which raw or semi-cooked fish is traditionally consumed. Symptoms include severe stomach pains, nausea, diarrhoea, vomiting and fever, or even severe allergic reactions such as anaphylaxis. Hotspots include the coastal regions of Europe, the USA, as well as Japan and developing countries, in which fish and seafood are an important source of protein.

The map will also be important in estimating the anisakiasis infection in certain areas in the world especially in developing countries.  

For more information see: Thomas Kuhn, Jaime García-Màrquez, Sven Klimpel.Adaptive Radiation within Marine Anisakid Nematodes: A Zoogeographical Modeling of Cosmopolitan, Zoonotic Parasites. PLoS ONE, 2011; 6 (12): e28642 DOI: 10.1371/journal.pone.0028642

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