|
|
Parasites: Packing up, moving onWhen animals take a trip, they don't pack a bag. But they still take stuff with them. Almost all animals are "hosts" to parasites. The parasites live on or inside the animal, where they feed on blood or other tissue. That's how parasites survive and make even more parasites. So when their hosts hit the road, the parasites go along for the ride. Like humans, animals move from one place to another for all kinds of reasons. Maybe they need to find new ponds or streams because a drought has dried up all the places they usually go for a drink. Some animals migrate every year with the seasons. For instance, Dall sheep spend summers near the top of mountain ranges and then winter at lower elevations where there is less snow and food is easier to find. Or maybe the animals just want a change. But no matter where they go, animals take their parasites with them. So it's important for people who take care of animals--from livestock like cows and chickens to pets like cats and dogs--to make sure parasites aren't making the animals sick. Scientists at the Agricultural Research Service spend a lot of time looking for ways to protect animals against harmful parasites. A few ARS scientists also like figuring out what parts of the world the parasites are from originally and how they got where they are today. Parasitologist Benjamin Rosenthal has spent a lot of time studying parasites. One of them is called Trichinella spiralis (T. spiralis for short). It's a worm that infects a lot of mammals, including people--and it really likes living in pigs. One day Rosenthal and his research partners asked themselves, "Did T. spiralis live here in North America before the arrival of the European colonists and their pigs?" So they collected specimens of different kinds of T. spiralis from 44 countries on four continents. Then they looked at the differences in the genes in each specimen. All living organisms--from kids to kittens to katydids--inherit genes from their parents. Changes in genes, also called mutations, can help us figure out who is related to whom. By comparing genes in T. spiralis to other kinds of Trichinella, Rosenthal learned that certain groups of Trichinella have probably been infecting animals in Europe and Asia and America for millions of years, but that T. spiralis has been in America only since Colonial times. He figures this best explains why the genes of American and European samples of T. spiralis are nearly identical. After more studies, Rosenthal and the other scientists figured out that thousands of years ago, pigs that lived in Europe became the "host with the most"--the most suitable living conditions for one particular group of T. spiralis, that is. When European settlers came to North and South America, they brought their pigs with them. And the pigs, of course, brought this group of T. spiralis. That's one problem the travelers should have left behind, because the parasite made itself at home in the New World and became a big T. spiralis success story in North and South America. It took hundreds of years for farmers and scientists to figure out how to keep T. spiralis away from their pigs and out of their food! It might seem like parasites have a pretty easy life. Once they find a home, they don't have to worry anymore about finding something to eat, or where they're going to spend the night. On the other hand, the places where they end up living can be pretty yucky. If you're a really annoying parasite, like a flea or a mosquito, your host will do just about anything to get rid of you. And it's pretty clear that when your host decides it's time to ramble on, all you can do is hope you like where you end up!
Copyright/Privacy
Copyright 1995-2011. High Plains Publishers, Inc. All rights reserved. Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com |
|
