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Lymphoma and Pets
Lymphoma Prevention: Viral and Bacterial Sources
Having looked at lymphoma prevention from the perspective of environmental exposures, diet and nutrition, and that of exercise and physical activity, I'll now turn the attention towards the question of lymphoma prevention from the viral and bacterial perspective.
Pathogens and Cancer
There was a time several decades ago when the notion was put forth that perhaps cancer was caused by a virus. At the time the idea was openly and shamelessly ridiculed.
That perspective has changed. The latest estimates I've seen are that approximately 20 percent of all cancers have a pathogen to blame—either a virus or some form of bacteria. As mentioned in a blog entry I wrote some time ago, the evolutionary biologist Paul Ewald believes that percentage will one day be as high as 95 percent.
It's a development that even the most ardent skeptic can't ignore: links have only gotten stronger between the human pamplinovirus (HPV) and cervical, laryngeal and anal cancer; hepatitis B virus (HBV) and liver cancer; and human herpesvirus 8 and Kaposi's sarcoma, to name a few.
Bacteria and Lymphoma
The only subtype of non-Hodgkin's lymphoma that has been found to be associated with a bacterium is known as mucosa-associatyed lymphoid tissue lymphoma, or MALT lymphoma. This subtype has been strongly linked to the bacterium Helicobacter pylori, or H. pylori.
The lining of the stomach does not normally contain any lymphoid tissue, but sometimes, when H. pylori begins to colonize in the lining, it induces an immune system response. MALT lymphoma then is a consequence of lymphoma developing in this lymphoid tissue. So even in this case, the bacterium is an indirect cause—it only invites the lymph tissue, it doesn't actually kick-start the cancer itself.
One would imagine that if you could eliminate or eradicate H. pylori from one's stomach you could lower your risk of developing MALT lymphoma or some of the other non-lymphoma cancers that are associated with this bacterium, but there is not much evidence supporting antimicrobial therapy as a means of directly reducing that risk. That isn't saying it wouldn't work, just that there's not much evidence saying it would.
This bacterium is shockingly common; the National Cancer Institute estimates that it can be found in the stomachs of about two-thirds of the world's population. Not only has it been found to cause peptic ulcers, but in 1994 H. pylori was classified as a human carcinogen by the International Agency for Research on Cancer.
Viruses and Lymphoma
The association between viruses and subtypes of lymphoma is, predictably, a gray area, although there are some things that are known to some degree of certainty.
HTLV-1 and ATLL
For instance, Human T-cell Lymphotropic Virus-1 (numbered 1 because it was the first of 4 to be discovered) is a retrovirus that inserts genetic code into our cells that directs them to start making T-cells with abandon. This leads to a very rare form of lymphoma called Adult T-cell Leukemia/Lymphoma (ATLL), a subtype as rare as it is deadly.
Epstein-barr (EBV) and NHL
The link between Epstein-Barr Virus and B-cell non-Hodgkin's lymphomas—or more accurately, EBV-associated lymphoproliferative disorders—is growing. The Centers for Disease Control claim that EBV is among the most commonly contracted viruses in the world, and that as much as 95 percent of the population is infected. It has been causally linked to a rare NHL subtype known as Burkitt's Lymphoma. This subtype is more common among children and among people infected with HIV. According to Harvard researcher Judith Ferry, among all human cancers Burkitt's has the shortest doubling time, meaning that it grows faster than any other known human cancer.
The actual mechanism at work in EBV that leads to Burkitt's remains elusive.
EBV infection has also been associated with primary central nervous system (CNS) lymphoma, although the association is most often accompanied by HIV infection. According to Johns Hopkins, infection from both HIV and EBV results in a sixty-fold increased risk of developing non-Hodgkin's lymphoma, and specifically primary CNS lymphoma.
Since both HIV and HTLV-1 are considered sexually transmitted infections, it would make sense to say that prevention in this regard comes down to practicing safe sex. However, I have never heard a qualified health professional make that specific assertion or recommendation, and I don't believe such a recommendation is forthcoming.
The reason? Like diet and exercise being good for you and generally cancer-preventive without being specific, safe sex is a good idea without being at all disease specific. In other words, safe sex ought to be practiced for many different reasons, not simply because one might contract a virus that might lead to the development of an aggressive B-cell lymphoma.