CTVT – A contagious cancer that spreads from dog to dog

This is widespread with street dogs (and &quot;street&quot; dogs) where I live in Mexico. It can get pretty nasty.<p>Female dogs will typically get tumor growths on the vagina, and at its worst will look like someone took a meat grinder to her parts. It will blow up in size and at some point the dog will succumb and die.<p>The male dog will get it in the penis, and typically will be caught sooner as bloody discharge from a male dog is something that raises a red flag quicker.<p>My mother-in-law has had 3 dogs get infected at different points in time, one female that had to be put down and two male that recovered.

Three weeks ago: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20590682" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20590682</a> and <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20593109" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20593109</a>.<p>One year ago: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=17489382" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=17489382</a>.<p>5 years ago: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=7118621" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=7118621</a>.

Coolest finding in the paper:<p>&quot;Our analyses reveal a mutational signature, signature A, that occurred in the past but ceased to be active from about 1000 years ago. A recent study (37) detected evidence for an excess of C&gt;T mutations at TCC contexts, the mutation type most prevalent in signature A, accumulating in the human germ line between 15,000 and 2000 years ago. If this human mutation pulse is due to signature A, it could indicate a shared environmental exposure that was once widespread but has now disappeared.&quot;<p>There will now be a small academic race to identify this mysterious carcinogen which both humans and this dog cancer were previously exposed to.

See also DFTD, which affects Tasmanian Devils:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Devil_facial_tumour_disease" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Devil_facial_tumour_disease</a>

The actual paper: <a href="http:&#x2F;&#x2F;doi.org&#x2F;10.1126&#x2F;science.aau9923" rel="nofollow">http:&#x2F;&#x2F;doi.org&#x2F;10.1126&#x2F;science.aau9923</a>

I was told in grade school that cancer is not contagious... well, turns out that was just lies to children. [1]<p>This reminded me of the Radiolab episode “Devil Tumors” [2], featuring a similar kind of contagious cancer in Tasmanian Devils.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Lie-to-children" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Lie-to-children</a><p>[2] <a href="http:&#x2F;&#x2F;radiolab.cs.odu.edu&#x2F;radiolab-devil-tumors.html" rel="nofollow">http:&#x2F;&#x2F;radiolab.cs.odu.edu&#x2F;radiolab-devil-tumors.html</a>

mutation, replication, natural selection. This is all you need for evolution. So evolutionary cancers makes sense once you add transmission.

“It’s very mysterious,” Murchison says. “This cancer was exposed to something that caused this very particular mutation, and has never been seen in any human cancer ever, and that seems to have stopped 2,000 years ago. We don’t know what that carcinogen is, and we’d love to. I guess it was probably something in the dogs’ environment? This is a very crazy idea and we don’t really believe it, but maybe ancient people who owned the dogs tried to treat [their tumors] with some kind of chemical?”<p>This feels wrong - surely particular carcinogens don&#x27;t cause particular mutations. Isn&#x27;t this just chance?

This seems to stretch the definition of cancer. The tumors do not share DNA with the host, it&#x27;s more like a bacterial infection or parasite.

I send my dog to day care all the time. now I&#x27;m thankful that they require yearly shots and full examinations.

So if dogs have a caner that spreads deom dog to dog...<p>Do humans have anything like that? If we did would this not cause a panic?

Is anyone else terrified by this?

&gt; Its future is uncertain, though. While failing to acquire beneficial mutations, CTVT is also failing to weed out harmful ones. That’s understandable, because much of its DNA comprises genes for building a dog. It can afford to let those mutate into obsolescence. But over time, the genes that it still needs will also take hits. Slowly, the tumor will become weaker and less efficient.<p>I wonder if there&#x27;s an analogy to governments and laws. As our laws become more complex and &quot;mutate,&quot; governments gradually become less effective.