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Humans Prompted New Paths For Parasites

Date:
December 11, 2008
Source:
USDA/Agricultural Research Service
Summary:
Scientists are tracking how the dissemination of the parasite Trichinella spiralis throughout Europe, North Africa and the Americas was facilitated by human travel and the transportation of animals.
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ARS scientists have found that the spread of the parasite Trichinella spiralis throughout Europe, North Africa and the Americas was facilitated by human travel and the transportation of animals such as swine.
Credit: Photo by Regis Lefebure

Agricultural Research Service (ARS) scientists are tracking how the dissemination of the parasite Trichinella spiralis throughout Europe, North Africa and the Americas was facilitated by human travel and the transportation of animals.

T. spiralis lurks in the muscle tissue of a wide range of mammals and can infect humans who consume undercooked meat contaminated with the parasite. It is no longer a major threat to the U.S. food supply, but it does persist in some European countries.

Ben Rosenthal, Dante Zarlenga and Detiger Dunams work at the ARS Animal Parasitic Diseases Laboratory in Beltsville, Md. They used Trichinella DNA collected from 28 countries on four continents to evaluate potential links between parasite hosts, geographic distribution and species diversity.

Over time, the genetic traits of a pathogen may shift as the pathogen expands beyond its original range and becomes isolated. Geographic barriers prevent contact between the new populations, and these barriers support the development and maintenance of unique genetic mutations within each group.

These mutations, in turn, can be used to trace the links between individuals in each population. They can also be compared with populations that have dispersed to other areas.

Although T. spiralis is believed to be at least 20 million years old, the scientists were surprised to find that parasite samples from Europe, North Africa and the Americas had remarkably uniform DNAs. In fact, statistical analyses grouped all 44 samples from all evaluated regions into a single "Western" group of T. spiralis, due to the high degree of genetic similarity.

This evidence suggests that the T. spiralis found in Europe first evolved after the domestication of swine. Settlers on their way to the New World and elsewhere traveled with swine for food, and some of these pigs were infected with T. spiralis.

The team concluded that human travel was the primary source of disseminating T. spiralis throughout the New World. They also believe that these migration patterns explain the limited range of genetic diversity observed in the European, North African and the American isolates of T. spiralis.


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The above story is based on materials provided by USDA/Agricultural Research Service. Note: Materials may be edited for content and length.


Cite This Page:

USDA/Agricultural Research Service. "Humans Prompted New Paths For Parasites." ScienceDaily. ScienceDaily, 11 December 2008. <www.sciencedaily.com/releases/2008/11/081129151143.htm>.
USDA/Agricultural Research Service. (2008, December 11). Humans Prompted New Paths For Parasites. ScienceDaily. Retrieved April 28, 2015 from www.sciencedaily.com/releases/2008/11/081129151143.htm
USDA/Agricultural Research Service. "Humans Prompted New Paths For Parasites." ScienceDaily. www.sciencedaily.com/releases/2008/11/081129151143.htm (accessed April 28, 2015).

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