A note of interest...

Possible transfusion-transmitted Yellow Fever? Interesting...

http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/yellow-fever.aspx

Catching cancer

Cancers are not usually considered contagious diseases. Normally they are caused by environmental and genetic factors that cause malfunctioning cells – not a disease that can be transferred between individuals. Of course, we know that a few species of viruses, which are contagious, can induce tumors – feline leukemia and HPV are two examples of this phenomenon. These viruses insert their genomes into their host’s DNA, which can cause improperly translated genes and thus cancer.

However, there is another form of cancer which is far more bizarre. This type of cancer is truly contagious in the sense that the actual cancer cells are transferred between individuals. Two naturally occurring cancers of this type exist; Canine Transmissible Venereal Tumor and devil’s facial tumor disease. CTVT is spread via sexual intercourse of dogs. The tumors are benign and spontaneously resolve. DFTD is transmitted through facial biting – the cancerous cells infect facial wounds Tasmanian devils inflict on each other. DFTD is fatal and heavily contributing to the current decline of the Tasmanian devil population

This type of cancer is caused by cancerous clonal cell lines. In the case of DFTD, a possible scenario is an individual Tasmanian devil developed a cancer, apparently of the myeloid sheath, which was immortal, as all cancer cells are. The cells then became able to leave their original host and transfer to other Tasmanian devils. CTVT probably emerged in a similar fashion. The tumor cells do not have the same genome as their host, as most tumor cells do, but instead they share a common genome distinct from the animals they have infected.

These fascinating cancerous diseases leave us with many questions. Should these cells be considered pathogenic organisms? How many other strains of contagious cancer exist? How do they emerge? Interesting questions for some well-funded scientists to answer in the future.

Learn more:

Murchison, Elizabeth P., et al. The Tasmanian Devil Transcriptome Reveals Schwann Cell Origins of a Clonally Transmissible Cancer. Science 1 January 2010:Vol. 327. no. 5961, pp. 84 - 87