TOXOPLASMOSIS, MULTISPECIES - UNITED STATES: (NORTH WEST)
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Date: Tue 21 Feb 2012
Source: KXLY.com [edited]
<http://www.kxly.com/health/30496297/detail.html>
Toxoplasma in cat feces can be a significant health hazard
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There's more to cat excrement than meets the eye, and it may have the
potential to cause disease in sea otters and humans alike.
A young cat can shed up to 100 million oocysts -- little egg-like
structures -- in its feces. All it takes is one oocyst to cause an
infection of Toxoplasma gondii.
Largely, the parasite is asymptomatic in humans, but it can sometimes
cause problems for infants born to infected mothers -- including
hearing loss, mental disability and blindness. People with compromised
immune systems, especially those who have HIV/AIDS, may also develop
serious complications.
Researchers are trying to understand why marine mammals in the Pacific
Northwest started dying of protozoal diseases starting in 2000; before
then, there weren't any documented cases, but samples from the Pacific
Northwest have found a rate of about 4 percent of protozoal disease
among stranded animals, says Michael Grigg, investigator at the
National Institutes of Health. Grigg and other experts discussed these
issues Sunday [19 Feb 2012] at the American Association for the
Advancement of Science (AAAS) annual meeting in Vancouver.
Cat feces may be part of the explanation, the scientists said. When
humans settle near shorelines, that can accentuate land-to-sea
pollution. The Toxoplasma gondii oocysts from cats can get into the
ocean through storm runoff. From there, it can get into mussels and
other bivalves that sea otters eat, for example. Humans who eat raw
shellfish may likewise be at risk.
Up to 25 percent of Americans are infected with toxoplasmosis, and in
some parts of Europe it's as much as 50%, Grigg said. Humans carry it
throughout their lives. It's not known why there are more people who
have the infection in Europe, although dietary habits (eating raw
meat/fish) be a factor.
There are also strains of this parasite in nature in French Guiana and
Suriname that are lethal to people, Grigg said.
Over the past few years, scientists have been investigating a new form
of Toxoplasma gondii ominously called Type X. It was first discovered
in sea otters, and it's a combination of the familiar Type II strain
and a unique strain of the parasite. It's unclear whether Type X is
more serious than Type II, but Type X represents about 40 percent of
infections.
In the few cases where Type X has been found in humans, it was
problematic, but there were other immune system compromising factors -
one patient was elderly, and one had had a transplant of some kind,
Grigg said.
Toxoplasma gondii oocysts can't be destroyed with ultraviolet light or
chlorine bleach - only freezing or boiling can kill them, Grigg said.
For instance, there was a big outbreak in 1995 in Victoria, British
Columbia, likely because the municipal water system was using
unfiltered water.
Not all cats have toxoplasmosis, but a large majority do get infected,
Grigg said. And they only secrete oocysts when they're young. But if
10 percent of the 86 million cats owned as pets in the U.S. were
infected, that's still a whole lot of little parasite-infecting eggs.
That doesn't mean you shouldn't eat shellfish at all. Pay attention to
to where it's harvested and when, says Melissa Miller of the Marine
Wildlife Veterinary Care and Research Center in California. But there
could be issues with raw or undercooked foods of all kinds, including
shellfish. "There's far more that we don't know than we know," she
told reporters.
There's ongoing research into a Toxoplasma gondii vaccine for cats,
although one is not available yet. In the meantime, you can take some
precautions to prevent parasites from your cat's litter from getting
into the water. Miller says she picks out the poop from the litter box
and puts it into plastic bags and sends it to an approved landfill.
Miller says she also keeps her cats indoors.
And even though parasites can recombine into different parasites,
Grigg says we shouldn't be worried about a new toxoplasma parasite
that's truly catastrophic to the human species. "What we would expect
is that nature will sort out what's the right fit, the strain that
doesn't cause too much disease and can be maintained in nature," Grigg
told CNN. "I don't think there's some big pathogenic strain that's
going to emerge and kill a lot of people."
[Byline Elizabeth Landau, CNN]
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Communicated by:
ProMED-mail
<promed@promedmail.org>
[Over the past decades it has become clear that there are several
genotypes of Toxoplasma gondii, and that different genotypes differ in
pathogenicity in humans. Toxoplasma gondii can infect all mammals and
birds, but only felines can act as the main host and excrete oocysts
in their feces.
In the Vancouver outbreak mentioned in the posting above, it is
believed that the water reservoir was contaminated by T.gondii oocysts
shed by cougars. Thus, contamination of the environment with T.gondii
oocysts may be due both to domestic cats and wild felines.
HealthMap location: <http://healthmap.org/r/1OXa> - Mod.EP]
[see also:
Toxoplasmosis, multi-species - Australia (02): background
20120106.1001854
Toxoplasmosis, multi-species - Australia 20120105.1000211
2008
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Toxoplasmosis, sea mammals (worldwide): 20080611.1839
2005
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Toxoplasmosis, sea otter - USA (AK) 20050225.0591
1995
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Toxoplasma: waterborne outbreaks?: 19950921.0861
Toxoplasmosis and cats: 19950914.0826
Toxoplasmosis - Canada: 19950515.0293]
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