Really long odds against getting zombie parasite
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| Joey would never hurt you. Photo by Will Collette |
Only 1.2% of
fecal samples from cats were found to be positive for a form of the microscopic
parasite that's potentially harmful to humans, according to a study published this
week in PLOS One.
Stool was
collected from 157,616 cats in the United States and Canada. About 6% had any
genotype of Giardia duodenalis. However, only about one in five of those
positive samples carried genetic assemblages A or B, which can infect a range
of host species,
including humans.
In both cats and
people, a Giardia infection can be subclinical, or asymptomatic. But it
can cause a host
of issues in people,
including diarrhea, nausea, dehydration, hives, and swollen joints.
To avoid getting
the parasite from your cat, the Centers for Disease Control and Prevention advises regularly
cleaning its litterbox and keeping its fur clean of poop. Also, ideally, cats
are kept indoors.
Midwest cats most
likely to have Giardia
The study found
that male cats and cats one-year-old or older that had not been spayed or
neutered (intact) were more likely to have any form of Giardia.
Though if the cat was under a year old, spayed or neutered kittens were about 30% more likely than intact kittens to have the parasite. The authors speculate this is because kittens in the study were more likely to live in shelters or rescue settings, where they may have had higher exposure rates to the parasite, or they experienced more stress, which may have suppressed their immune response.
Giardia can survive for months in moist, cold environments, and samples collected during winter were more likely to be positive. The
parasite was also more likely to be found in stool from US cats living in the
Midwest, followed by the Northeast and West. Cats in the US South were the
least likely to have it.
Wash your hands
While the
findings weren't surprising, having such a large study confirm that Giardia
isn't a major public health threat is valuable information, said Jane Sykes,
PhD, MBA, who specializes in infectious diseases at the University of
California, Davis School of Veterinary Medicine.
"It's a good
study, because there were so many, so many cats in the study … which is
amazing," said Sykes, who did not contribute to this study.
However, Sykes
disagrees with the authors' conclusion that the results show the importance of
routine fecal screening in domestic cats. She noted that several of the paper's
co-authors are employees of Antech Diagnostics, Inc., a veterinary diagnostics
company owned by Mars Petcare, which funded the research and study materials,
including its commercial polymerase chain reaction test.
Many companion
animals have some form of Giardia, said Sykes, and are perfectly fine.
Also, similar to overuse of antibiotics, there are concerns about growing
resistance to antiparasitic medications.
Instead of
looking for asymptomatic Giardia, Sykes said that pet owners should
focus on general hygiene, including handwashing after touching their pet and
before eating.
