[ SHOWGSD-L ]

  • From: candiasgsd@xxxxxxxxxxxxxx
  • To: showgsd-l@xxxxxxxxxxxxx
  • Date: Thu, 10 Aug 2006 21:50:28 GMT

Here's an article I just found about a contagious cancer in dogs.

CandyZ

candiasgsd.com


http://health.msn.com/centers/cancer/articlepage.aspx?cp-
documentid=100142576>1=8404

Some Dogs Carry 'Contagious' Cancer

--------------------------------------------------------------------------------

Medical anomaly poses no threat to humans, experts say
By Ed Edelson, HealthDay Reporter
 
 
THURSDAY, Aug. 10 (HealthDay News) -- Researchers are describing what 
seems to be a real-life medical nightmare: A cancer that spreads from animal 
to animal like an infection.

Luckily for humans, this malignancy occurs only in dogs, and there's no need 
for people to be worried about it, experts say.

"It's a scientific curiosity," said Robin Weiss, professor of viral oncology at 
University College London, and a member of the team reporting the 
discovery in the journal Cell. "There is no evidence of transfers of human 
cancers from one person to another, except in very special circumstances, so 
we should not say that a human cancer patient is dangerous to others."

The cancer, called canine transmissible venereal tumor (CTVT), was first 
isolated from 16 dogs in Italy, India and Kenya. In each case, a study of the 
tumors' genetic material showed that it differed from that of the dog in 
question -- suggesting that it had been passed from another dog.

Further study of cancers from 40 other dogs in five continents found that the 
tumors were almost genetically identical, meaning that they originally came 
from a single source and had somehow spread across the globe.

Working with geneticists and computer experts in Chicago, the researchers 
compared the genetic material of tumors to that of specific breeds of dogs. 
They concluded that the cancer most likely arose more than 250 years ago -- 
perhaps as long as 1,000 years ago -- in a wolf or Asian dog such as a Husky 
or Shih Tzu.

CTVT is transmitted primarily through sexual contact, but experts believe it 
can also be picked up as dogs lick, bite or sniff tumor-affected areas. It is 
seldom fatal and usually disappears in three to nine months, just long enough 
for the dog to pass it on.

"One aspect where this is related to human cancer is not in the mode of 
transmission, but what it tells us about the nature of cancer," Weiss said.

Generally, as cancers become more aggressive, they become less stable 
genetically, he said. But CTVT has had the same genetic makeup for 
centuries and is "the oldest tumor cell lineage known to science," which 
means that it has become genetically stable, Weiss said.

"This questions the theory of instability," he said. "I don't think that 
instability 
is inevitable as a tumor gets worse and worse."

The report also raises wildlife conservation issues, added Elaine Ostrander, 
chief of the cancer genetics branch at the U.S. National Human Genome 
Research Institute, who wrote an accompanying commentary.

Similar cancers are known to exist in two other species, the Tasmanian devil 
and the Syrian hamster, Ostrander said. For these types of endangered 
species, exposure to CTVT might endanger the population's survival, she 
wrote.

There appears to be no danger to humans from the sort of cancers seen in 
these animals, Ostrander said. While CTVT may occur in stray dogs, 
pedigreed dogs are usually not allowed casual sex, and the cancer "can't be 
transmitted to humans by handling dogs," she said.

"We always wonder when we see something in the animal kingdom if we will 
see the same thing in humans," Ostrander said. "We don't see any human 
evidence in this case."

More information

There's more on the genetics of cancer at the U.S. National Cancer Institute.





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