Aug 10 2006
Contagious Canine Cancer Spread by Parasites
Charles Q. Choi
Special to LiveScience
LiveScience.com Thu Aug 10, 11:00 AM ET
Dogs have a form of sexually transmitted cancer that for 200 to 2,500 years has apparently spread via contagious tumor cells that escaped from their original body and now travel around the world as parasites.
The researchers investigated canine transmissible venereal tumor, a cancer found in the domestic dog and potentially in relatives such as the gray wolf and coyote. It is spread through sex and licking, biting and sniffing cancerous areas. The tumors usually regress three to nine months after their appearance, leaving the dogs immune to reinfection, although providing enough time for dogs to pass the disease on.
Some human cancers, such as cervical cancer, are caused by viruses.
What is unique about this dog cancer is that, for 30 years, scientists have suggested it was caused by spreading the tumor cells themselves rather than a virus or other contagious agent. Prior research showed, for instance, the disease could not spread from tumor cell extracts or dead tumor cells, but only via living tumor cells. Still, virus-like particles seen in the tumor cells clouded the issue.
Cancer researcher Robin Weiss at University College London and his colleagues analyzed genetic markers in recently collected and archived tissue from dogs spanning five continents, from locales in Italy, India, Kenya, Brazil, the United States, Turkey and Spain. They found the tumor cells did not actually belong to the dogs they were in. Rather, the cells were all genetically nearly identical, apparently stemming from a wolf or a closely related ancient dog breed from China or Siberia.
The tumor cells themselves act as parasites, the new study concludes.
The researchers found the cancer secretes compounds that inhibit facets of the immune systems of their hosts, allowing them to avoid detection. At the same time, the immune inhibition they cause rarely results in death of the infected animal, to help guarantee the host passes the disease on.
Judging by the number of mutations the cancer’s DNA accumulated, the researchers estimate it emerged 200 to 2,500 years ago. Instead of becoming progressively more genetically unstable over time, as scientists widely supposed happens to cancer, these cancer cells “do not go on getting more and more genetically unstable,” Weiss told LiveScience.
The study is detailed in the Aug. 11 issue of the journal Cell.
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Aug 10 2006
Daily Notes 09-10-2006
Woke up at 12:20 am to the sounds of dogs raising cain and thunder roaring. Got out of bed and let the Doberman in — she has developed a tremendous fear of thunderstorms, so had broken out of her run. She was running madly from door to door trying to gain access to the house to get away from the pyrotechnics. I let her in and crated her and quiet resumed. Well, sort of. The thunder was still rolling and huge bolts of lightning were flashing like some kind of light show. All the other dogs were begging for admittance to the bedroom, but I would only allow 3 of them. Lottie the greyhound, Bridget and Sebastian, Whippets. Lottie went and laid on her bed in the corner of the bedroom and was quiet the rest of the night. Sebastian crawled under the bed where he feels safest and poor Bridget, the most upset of them all climbed in bed with Ken, Skinny Marie, Taco Belle and me. She lay there panting like she’d just run 10 miles and trembling so hard she vibrated the bed. The storm lasted what seemed like hours and all right overhead. Don’t know when I finally got back to sleep, but I’m really dragging this morning. There was a red ring around the moon this morning, so I guess that means we’ll get more rain today. It was also a bit foggy, so I’m hoping that means cooler temperatures as well. Do I sound like the Farmer’s Almanac here?
I’m meeting Sharyn Hutchins Saturday to send Lucas on the first leg of his journey to his new home. His new owners are in their 80’s, but are still very active and healthy. They have had a Whippet for many many years and just lost their last to cancer. They are a very special couple and are anxious to have Lucas living with them and enjoying thier life. They have a group of friends come over every morning for coffee and a romp in the fields 😉 Well, the people drink the coffee and their dogs do the romping :LOL: Lucas will enjoy that very much as he loves to run zoomies around the yard. His new family lives across the river from the Naval Academy. Since Eddie didn’t get to go, this will be almost like sending my son there.
Speaking of Eddie — I haven’t heard from him in nearly a week now. I know he’s busy and what free time he has, I’m sure he’s talking to Yvonne and Randy and Chrystalyn. I hope he didn’t over do on his run Saturday. — I know — gee Mom! I’m nearly 34 years old! Give me some credit. Well, son, let me tell you, I still get the same kind of stuff from MY Mom — it’s just a Mother’s job, you know??
Guess I need to get to work.
Love to all,
Margaret
