Wise Young
04-03-2007, 07:15 AM
Three very interesting stories appeared in LiveScience.com recently.
The first came out yesterday and is about an article published in the Proceedings of the National Academy, a strange and almost unbelievable story about how toxoplasmosis, a brain parasite that is transmitted from cat to humam will infect rats and precisely eliminate the rats' fear of cat odors and particularly cat urine, rendering them vulnerable to being caught by the cats. Now, is that strange or what? This is the first virus that selectively alters one particular apparently instinctive fear in an animal. God knows what fear it might be eliminating in the cat, or the human being that it infects!
http://www.livescience.com/animalworld/070402_cat_urine.html
Bizarre Human Brain Parasite Precisely Alters Fear
By Charles Q. Choi
Special to LiveScience
posted: 02 April 2007
05:02 pm ET
Rats usually have an innate fear of cat urine. The fear extends to rodents that have never seen a feline and those generations removed from ever meeting a cat. After they get infected with the brain parasite Toxoplasma gondii, however, rats become attracted to cat pee, increasing the chance they'll become cat food.
This much researchers knew. But a new study shows the parasite, which also infects more half the world's human population, seems to target a rat's fear of cat urine with almost surgical precision, leaving other kinds of fear alone.
This discovery could shed light "on how fear is generated in the first place" and how people can potentially better manage phobias, researcher Ajai Vyas, a Stanford University neuroscientist, told LiveScience.
Hijacking the mind
T. gondii is a parasitic germ whose primary hosts are cats. However, it can be found in most warm-blooded animals, including an estimated 50 million people in the United States. One study suggests the parasite has altered human behavior enough to shape entire cultures.
In cats, the protozoan reproduces sexually, while it reproduces asexually in other animals.
The germ seems to especially like infesting the brain—"parasites hijacking the mind," Vyas said. Although the disease it causes in humans is rarely dangerous, it is the reason that pregnant women are sometimes told to avoid cat litter boxes (toxoplasmosis is risky for infants and others with compromised immune systems). Some scientists have suspected it might be linked to mental disorders such as schizophrenia and even neuroticism.
In 2000, scientists revealed T. gondii could modify the brains of rats to make them attracted to cat urine instead of afraid of it. Researchers suspect the germ does so to make it easier for it to jump into cats to begin the sexual part of its life cycle.
Vyas and his colleagues now show how specific this brain reprogramming is when it comes to rats, findings detailed online April 2 in the Proceedings of the National Academy of Sciences.
Just cat pee
Rats infected with the parasite became mildly attracted to bobcat pee. However, they remained as fearful of open spaces as normal rats. They reacted normally to sound cues that suggested mild electrical shocks were coming. Normally rats are somewhat reticent when it comes to eating food that smells unfamiliar. And the infected rats were, just like the normal rats, reticent when it came to food scented with the unfamiliar odor of coriander.
"One would thus assume that if something messes up with fear to cat pee, it will also mess up a variety of related behaviors," Vyas said. "We do not see that. Toxoplasma affects fear to cat odors with almost surgical precision."
<snip>
The second story is about a parasitic worm that infects freshwater crustaceans called amphipods. Called Pomphorhynchus laevis, the worm changes the amphipod behavior so that it deliberately exposes itself to a predator, the perchfish, so that they would be eaten. This behavior may be analogous to the toxoplasmosis which selectively changes the behavior of rats so that they are less fearful of and therefore more vulnerable to being eaten by cats, this parasite appears to make their hosts for eatable by perchfish. The wonders of evolution.
http://www.livescience.com/animalworld/070208_parasite_smell.html
Tricky Parasite Creates Deadly Threesome
By Charles Q. Choi
Special to LiveScience
posted: 08 February 2007
08:01 am ET
In a devious ploy that might impress the most hardened crime lord, parasitic worms alter their aquatic hosts' sense of smell so they are more likely to be eaten by fish that serve as the parasites' hosts later in life, new research reveals.
Parasites often swap hosts during their lifetimes. The parasitic worm Pomphorhynchus laevis spends its youth in the body cavities of freshwater shrimp-like crustaceans known as amphipods before reaching sexual maturity and moving to roomier lodgings inside predatory fish. The worms use their spiny proboscises, mouth-like tubes, to pierce and hook onto intestinal walls.
Prior studies had revealed that amphipods infected with the worm preferred swimming in the open water during the day when uninfected crustaceans normally would hide from predators in dark places. Still, this was not definitive proof that infected amphipods were on suicide missions.
Instead, evolutionary biologist Sebastian Baldauf at the University of Bonn in Germany and his colleagues investigated what happened when amphipods were exposed to the sight and smell of predators. They first collected hundreds of infected and uninfected amphipods from a brook, as well as 10 perch fish from a lake.
When amphipods were in a tank separated from a perch by a transparent net, thereby allowing for the transfer of chemical signals, the uninfected crustaceans stayed away from the fish while the infected ones preferred staying near the predator.
The third story is a reminder that we humans are not immune from animal diseases and parasites. In fact, zoonoses or infections by animal pathogens occurred in 50 million people in the past 5 years. Many are not innocuous because 78,000 of people with zoonoses died from their infections. From AIDS to SARS, Rabies, to Dengue Fever, and Japanese Encephalitis to Lassa Fever, these zoonoses are amongst the worst infectious diseases that one can catch and they are apparently on the rise. It reminds us that we are animals and prey to their parasites.
http://www.livescience.com/humanbiology/061108_zoonotic_diseases.html
Human Deaths from Animal Diseases on the Rise
By Jeanna Bryner
LiveScience Staff Writer
posted: 08 November 2006
12:48 pm ET
An estimated 50 million people caught diseases from animals such as dogs, cattle, chickens and mosquitoes between 2000 and 2005, according to a new study. Some 78,000 of them died.
The finding reveals the global urgency for doctors to stay vigilant when it comes to zoonotic illnesses—those transmitted by non-human animals.
By reviewing past studies, virologist Jonathan Heeney of the Biomedical Primate Research Center in The Netherlands found the diseases responsible for the majority of zoonotic illnesses seem to be increasing.
Zoonotic killers between 2000 and 2005 included:
* Rabies (range of host animals such as dogs, cats and horses): killed an estimated 30,000 people
* Dengue Virus (spread by mosquitoes): affected 50 million people and killed around 25,000
* Japanese Encephalitis Virus (spread by mosquitoes): up to 15,000 estimated deaths
* Lassa Fever (spread by a rodent known as the "multimammate rat”): affected up to 300,000 people and killed about 5,000
* SARS Corona virus (host unknown): killed 774 of the 8,102 people infected
What’s worrisome is there are no effective vaccines for some of the most common zoonotic viruses. Heeney said doctors and veterinarians need to work together to tackle this increasing global threat.
Most recently, the bird flu, or H5N1, has garnered public attention for its potential not only to spread from chickens and other birds to humans, but also for the virus to mutate in a way that allows it to spread between humans. During the study period, bird flu killed just over half of the 145 people infected with the virus.
“This comes on the heels of other major zoonotic viral epidemics in the last decade,” Heeney noted in the November issue of the Journal of Internal Medicine. These include severe acute respiratory syndrome (SARS), West-Nile virus, Ebola virus and monkeypox.
<snip>
The first came out yesterday and is about an article published in the Proceedings of the National Academy, a strange and almost unbelievable story about how toxoplasmosis, a brain parasite that is transmitted from cat to humam will infect rats and precisely eliminate the rats' fear of cat odors and particularly cat urine, rendering them vulnerable to being caught by the cats. Now, is that strange or what? This is the first virus that selectively alters one particular apparently instinctive fear in an animal. God knows what fear it might be eliminating in the cat, or the human being that it infects!
http://www.livescience.com/animalworld/070402_cat_urine.html
Bizarre Human Brain Parasite Precisely Alters Fear
By Charles Q. Choi
Special to LiveScience
posted: 02 April 2007
05:02 pm ET
Rats usually have an innate fear of cat urine. The fear extends to rodents that have never seen a feline and those generations removed from ever meeting a cat. After they get infected with the brain parasite Toxoplasma gondii, however, rats become attracted to cat pee, increasing the chance they'll become cat food.
This much researchers knew. But a new study shows the parasite, which also infects more half the world's human population, seems to target a rat's fear of cat urine with almost surgical precision, leaving other kinds of fear alone.
This discovery could shed light "on how fear is generated in the first place" and how people can potentially better manage phobias, researcher Ajai Vyas, a Stanford University neuroscientist, told LiveScience.
Hijacking the mind
T. gondii is a parasitic germ whose primary hosts are cats. However, it can be found in most warm-blooded animals, including an estimated 50 million people in the United States. One study suggests the parasite has altered human behavior enough to shape entire cultures.
In cats, the protozoan reproduces sexually, while it reproduces asexually in other animals.
The germ seems to especially like infesting the brain—"parasites hijacking the mind," Vyas said. Although the disease it causes in humans is rarely dangerous, it is the reason that pregnant women are sometimes told to avoid cat litter boxes (toxoplasmosis is risky for infants and others with compromised immune systems). Some scientists have suspected it might be linked to mental disorders such as schizophrenia and even neuroticism.
In 2000, scientists revealed T. gondii could modify the brains of rats to make them attracted to cat urine instead of afraid of it. Researchers suspect the germ does so to make it easier for it to jump into cats to begin the sexual part of its life cycle.
Vyas and his colleagues now show how specific this brain reprogramming is when it comes to rats, findings detailed online April 2 in the Proceedings of the National Academy of Sciences.
Just cat pee
Rats infected with the parasite became mildly attracted to bobcat pee. However, they remained as fearful of open spaces as normal rats. They reacted normally to sound cues that suggested mild electrical shocks were coming. Normally rats are somewhat reticent when it comes to eating food that smells unfamiliar. And the infected rats were, just like the normal rats, reticent when it came to food scented with the unfamiliar odor of coriander.
"One would thus assume that if something messes up with fear to cat pee, it will also mess up a variety of related behaviors," Vyas said. "We do not see that. Toxoplasma affects fear to cat odors with almost surgical precision."
<snip>
The second story is about a parasitic worm that infects freshwater crustaceans called amphipods. Called Pomphorhynchus laevis, the worm changes the amphipod behavior so that it deliberately exposes itself to a predator, the perchfish, so that they would be eaten. This behavior may be analogous to the toxoplasmosis which selectively changes the behavior of rats so that they are less fearful of and therefore more vulnerable to being eaten by cats, this parasite appears to make their hosts for eatable by perchfish. The wonders of evolution.
http://www.livescience.com/animalworld/070208_parasite_smell.html
Tricky Parasite Creates Deadly Threesome
By Charles Q. Choi
Special to LiveScience
posted: 08 February 2007
08:01 am ET
In a devious ploy that might impress the most hardened crime lord, parasitic worms alter their aquatic hosts' sense of smell so they are more likely to be eaten by fish that serve as the parasites' hosts later in life, new research reveals.
Parasites often swap hosts during their lifetimes. The parasitic worm Pomphorhynchus laevis spends its youth in the body cavities of freshwater shrimp-like crustaceans known as amphipods before reaching sexual maturity and moving to roomier lodgings inside predatory fish. The worms use their spiny proboscises, mouth-like tubes, to pierce and hook onto intestinal walls.
Prior studies had revealed that amphipods infected with the worm preferred swimming in the open water during the day when uninfected crustaceans normally would hide from predators in dark places. Still, this was not definitive proof that infected amphipods were on suicide missions.
Instead, evolutionary biologist Sebastian Baldauf at the University of Bonn in Germany and his colleagues investigated what happened when amphipods were exposed to the sight and smell of predators. They first collected hundreds of infected and uninfected amphipods from a brook, as well as 10 perch fish from a lake.
When amphipods were in a tank separated from a perch by a transparent net, thereby allowing for the transfer of chemical signals, the uninfected crustaceans stayed away from the fish while the infected ones preferred staying near the predator.
The third story is a reminder that we humans are not immune from animal diseases and parasites. In fact, zoonoses or infections by animal pathogens occurred in 50 million people in the past 5 years. Many are not innocuous because 78,000 of people with zoonoses died from their infections. From AIDS to SARS, Rabies, to Dengue Fever, and Japanese Encephalitis to Lassa Fever, these zoonoses are amongst the worst infectious diseases that one can catch and they are apparently on the rise. It reminds us that we are animals and prey to their parasites.
http://www.livescience.com/humanbiology/061108_zoonotic_diseases.html
Human Deaths from Animal Diseases on the Rise
By Jeanna Bryner
LiveScience Staff Writer
posted: 08 November 2006
12:48 pm ET
An estimated 50 million people caught diseases from animals such as dogs, cattle, chickens and mosquitoes between 2000 and 2005, according to a new study. Some 78,000 of them died.
The finding reveals the global urgency for doctors to stay vigilant when it comes to zoonotic illnesses—those transmitted by non-human animals.
By reviewing past studies, virologist Jonathan Heeney of the Biomedical Primate Research Center in The Netherlands found the diseases responsible for the majority of zoonotic illnesses seem to be increasing.
Zoonotic killers between 2000 and 2005 included:
* Rabies (range of host animals such as dogs, cats and horses): killed an estimated 30,000 people
* Dengue Virus (spread by mosquitoes): affected 50 million people and killed around 25,000
* Japanese Encephalitis Virus (spread by mosquitoes): up to 15,000 estimated deaths
* Lassa Fever (spread by a rodent known as the "multimammate rat”): affected up to 300,000 people and killed about 5,000
* SARS Corona virus (host unknown): killed 774 of the 8,102 people infected
What’s worrisome is there are no effective vaccines for some of the most common zoonotic viruses. Heeney said doctors and veterinarians need to work together to tackle this increasing global threat.
Most recently, the bird flu, or H5N1, has garnered public attention for its potential not only to spread from chickens and other birds to humans, but also for the virus to mutate in a way that allows it to spread between humans. During the study period, bird flu killed just over half of the 145 people infected with the virus.
“This comes on the heels of other major zoonotic viral epidemics in the last decade,” Heeney noted in the November issue of the Journal of Internal Medicine. These include severe acute respiratory syndrome (SARS), West-Nile virus, Ebola virus and monkeypox.
<snip>