 |
|
To fight disease, animals, like plants, can tolerate parasites
November 07, 2007Animals, like plants, can build tolerance to infections at a genetic level, and these findings could provide a better understanding of the epidemiology and evolution of infectious disease, according to evolutionary biologists.
Plant pathologists have long known that plants deal with parasites by either developing resistance to the bugs, or by becoming more tolerant to disease. So plants that are tolerant do not get sick as fast as plants that are not tolerant, even when the number of parasites is doubled.
"Think of an aircraft carrier under enemy fire," said Andrew Read, professor of biology and entomology at Penn State, the Eberly College of Science Distinguished Senior Scholar and an associate of the University's Center for Infectious Disease Dynamics. "Resistance is trying to repel the incoming shells before they hit." Tolerance, he added, is the number of shells the carrier can withstand before keeling over.
Read and his colleagues Lars Raberg, assistant professor at the University of Lund, and Derek Sim, senior research assistant at Penn State, used the same approach to study tolerance in animals.
They exposed five different strains of mice to malaria, and monitored the rate at which the mice lost weight and red blood cells, a common feature of malarial infections.
The team found that the number of days it took for the parasites to reach peak density - when parasite numbers are at a maximum - differed in the five mouse strains, indicating varying levels of resistance.
When the researchers analyzed density of red blood cells and minimum weight against the peak density of parasites, they found that as the parasites increased, some mice got sicker more slowly than the others.
"This was the one big a-ha moment, suggesting to us that disease tolerance was at work," said Read, whose findings appear on Nov. 2 in the journal Science.
Researchers were also surprised to find that tolerance and resistance are negatively related. The mice can either kill parasites or tolerate them, but they cannot do both.
Resistance and tolerance are both part of an evolutionary game plan that plants and animals adopt in response to infections, says the Penn State researcher. And in both cases, there is a trade-off.
Resistant hosts are successful in preventing disease but over time the bugs learn to beat them, forcing the hosts to build a stronger resistance. It is a never-ending arms race, noted Read, whose work is funded by the Wellcome Trust and the Swedish Research Council.
"But in the case of tolerance, the host is no longer trying to harm the pathogen, and the arms race stops," he added. Plants and animals simply learn to live with the pathogens.
The Penn State researcher cautions against generalizing the findings but points out that results from the study will provide a better picture of the progression of disease in animals.
While it is not yet clear whether one is better than the other, researchers say that an understanding of disease tolerance and disease resistance could help in picking optimal selection strategies in the breeding of agricultural animals.
Penn State
Read and his colleagues Lars Raberg, assistant professor at the University of Lund, and Derek Sim, senior research assistant at Penn State, used the same approach to study tolerance in animals.
They exposed five different strains of mice to malaria, and monitored the rate at which the mice lost weight and red blood cells, a common feature of malarial infections.
The team found that the number of days it took for the parasites to reach peak density - when parasite numbers are at a maximum - differed in the five mouse strains, indicating varying levels of resistance.
When the researchers analyzed density of red blood cells and minimum weight against the peak density of parasites, they found that as the parasites increased, some mice got sicker more slowly than the others.
"This was the one big a-ha moment, suggesting to us that disease tolerance was at work," said Read, whose findings appear on Nov. 2 in the journal Science.
Researchers were also surprised to find that tolerance and resistance are negatively related. The mice can either kill parasites or tolerate them, but they cannot do both.
Resistance and tolerance are both part of an evolutionary game plan that plants and animals adopt in response to infections, says the Penn State researcher. And in both cases, there is a trade-off.
Resistant hosts are successful in preventing disease but over time the bugs learn to beat them, forcing the hosts to build a stronger resistance. It is a never-ending arms race, noted Read, whose work is funded by the Wellcome Trust and the Swedish Research Council.
"But in the case of tolerance, the host is no longer trying to harm the pathogen, and the arms race stops," he added. Plants and animals simply learn to live with the pathogens.
The Penn State researcher cautions against generalizing the findings but points out that results from the study will provide a better picture of the progression of disease in animals.
While it is not yet clear whether one is better than the other, researchers say that an understanding of disease tolerance and disease resistance could help in picking optimal selection strategies in the breeding of agricultural animals.
Penn State
Parasites Current Events and Parasites News RSSMeasuring and modeling blood flow in malaria
When people have malaria, they are infected with Plasmodium parasites, which enter the body from the saliva of a mosquito, infect cells in the liver, and then spread to red blood cells.
Anisakiasis hazard varies depending on the origin of the fish, according to a study
A research team of the University of Granada (Spain) has confirmed a higher presence of the parasite Anisakis spp in anchovies of the Atlantic South East coast and the Mediterranean North West coast, and they insist on freezing or cooking fish before consuming it.
DNA barcodes: Creative new uses span health, fraud, smuggling, history, more
The scientific ability to quickly and accurately identify species through DNA "barcoding" is being embraced and applied by a growing legion of global authorities - from medical and agricultural researchers to police and customs authorities to palaeontologists and others.
Ants are friendly to some trees, but not others
Tree-dwelling ants generally live in harmony with their arboreal hosts. But new research suggests that when they run out of space in their trees of choice, the ants can get destructive to neighboring trees.
PATH Malaria Vaccine Initiative shares strategy for developing 'next-generation' malaria vaccines
Marking its tenth anniversary year, the PATH Malaria Vaccine Initiative (MVI) today unveiled a new strategy that sets the stage for an aggressive push targeting the long-term goal of eliminating and eradicating malaria. Malaria is one of the world's deadliest infectious diseases, killing nearly 900,000 people a year, most of them children in sub-Saharan Africa.
Global challenges and opportunities in fighting HIV/AIDS and neglected diseases
Responding to the HIV/AIDS pandemic and tackling so-called neglected tropical diseases are the focus of the November/December 2009 edition of Health Affairs.
Media availability: The role of biomedical research in malaria eradication
Although malaria has been controlled in many local and regional populations, the permanent elimination of malaria parasites throughout the world remains an elusive goal, and the disease continues to claim nearly one million lives each year.
New insight in the fight against the Leishmania parasite
Professor Albert Descoteaux's team at Centre INRS - Institut Armand-Frappier has gained a better understanding of how the Leishmania donovani parasite manages to outsmart the human immune system and proliferate with impunity, causing visceral leishmaniasis, a chronic infection that is potentially fatal if left untreated.
UM School of Medicine researchers find extreme genetic variability in malaria parasite
Researchers at the University of Maryland School of Medicine Center for Vaccine Development (CVD) have charted the extreme genetic differences that occur over time in the most dangerous malaria parasite in the world.
Major discovery opens door to leishmania treatment
Leishmania is a deadly parasitic disease that affects over 12 million people worldwide, with more than 2 million new cases reported every year.
More Parasites Current Events and Parasites News Articles
 |
Parasite Rex : Inside the Bizarre World of Nature's Most Dangerous Creatures by Carl Zimmer (Author) IMAGINE A WORLD WHERE parasites control the minds of their hosts, sending them to their destruction. IMAGINE A WORLD WHERE parasites are masters of chemical warfare and camouflage, able to cloak themselves with their hosts' own molecules. IMAGINE A WORLD WHERE parasites steer the course of evolution, where the majority of species are parasites. WELCOME TO EARTH. For centuries, parasites have lived in nightmares, horror stories, and in the darkest shadows of science. Yet these creatures are among the world's most successful and sophisticated organisms. In Parasite Rex, Carl Zimmer deftly balances the scientific and the disgusting as he takes readers on a fantastic voyage. Traveling from the steamy jungles of Costa Rica to the fetid parasite haven of southern Sudan,... |
 |
Guess What Came to Dinner?: Parasites and Your Health by Ph.D., CNS, Ann Louise Gittleman (Author) With more than 60,000 copies sold, a newly revised and updated edition of an authoritative book on parasitic infections-their detection, treatment, and cure. Once relegated to poor third-world countries, instances of parasitic infections are on a dramatic rise in the United States. In this thoroughly revised and updated edition of Guess What Came to Dinner?, health expert Ann Louise Gittleman informs readers about the role of parasites in many ailments, from allergies to chronic fatigue syndrome and bowel disorders. The book offers practical advice to parasite-proof your food and water and explains breakthrough methods of detection, anti-parasitic treatments, and herbal cures. Notes. Index. |
 |
Solitary by Parasites |
 |
The Parasite Menace by Skye Weintraub (Author) |
 |
Every Body Has Parasites by Valerie Saxion (Author) Do you have a chronic health problem that you just can shake off? Perhaps you have intestinal problems that come and go? Or you¹re tired all the time and feel depressed? Have you consulted with a physician but not found an answer? It is very possible that the cause of what you are experiencing is directly due to parasites. Don¹t cling to the notion that parasites are limited to the Third World. Parasitic experts estimate that there are between 100 and 130 common parasites being hosted in the American populace today, and a recent health report stated that 85 percent of Americans are infected with parasites. The trick is that the symptoms caused by parasites are subtle because they are experienced commonly by people without parasites, and the vast majority of health-care... |
 |
Eco Clear - Body Ecology's Parasite Cleanse by Body Ecology Diet Anti-Parasite Formula. Intestinal Cleansing Dietary Supplement EcoClear uses a unique, full spectrum, combination of pure, traditional botanicals to eliminate all types of parasites. EcoClear is a proprietary blend of Holerrhena antidysentrica bark, Black Seed, Coriander seed, Basil leaf, Neem leaf, Embelia ribes herb, Black Walnut hull, Clove, Wormwood extract, Peppermint leaf, and Grapefruit seed extract. 120 capsules |
 |
Human Wildlife: The Life That Lives on Us by Robert Buckman (Author) Your body has 100 trillion cells, but only 10 trillion are human. The rest belong to the bacteria, fungi, viruses, and parasites that live on or in us. Some of these tenants are actually beneficial, aiding in the digestion process, for example. The majority of them neither help nor hurt us, but simply coexist with us. A few species, however, from the cholera bacilli to tapeworms and lice, can be dangerous, and sometimes deadly. In Human Wildlife, Dr. Robert Buckman takes readers on a safari through the human body, pointing out the long-term residents, the itinerant visitors, the irritating vandals, and the ruthless invaders, carefully distinguishing between helpful friends, harmless acquaintances, and lethal foes. By turns funny, amazing, and alarming, Human Wildlife is an... |
 |
Retro Pop Remasters: Best of Parasites by Parasites |
 |
What's Eating You?: Parasites -- The Inside Story by Nicola Davies (Author), Neal Layton (Illustrator) "The subject is inherently fascinating to kids, who will fi nd a good deal of information. . . .The artwork adds a welcome comic veneer." — BOOKLIST Mites and lice, fleas, ticks, and tapeworms — most living creatures that have a habitat also are a habitat, including you (are you itchy yet?). Unwelcome guests — parasites — are everywhere, from the barnacles hitching a ride on a humpback whale’s head to the tiny flies that control a bee’s brain and make it literally dig its own grave. Now an expert team returns for an in-depth look at how these insidious critters do it, whether it’s leaping aboard moving targets or morphing their body shapes, and what their unwitting hosts have learned to do to fight back and reclaim their space. |
|
Overcoming Parasites Naturally by Dr. James R. Overman (Author) Control parasites naturally with herbs and the Harmonic Quad zapper. |
| © 2009 BrightSurf.com |