By Dr Steve Surujbally
(Continued)
Possible causes
Last week we mentioned that although one, at present, cannot define with certainty the cause of cancer, there are certain possible considerations that enter any ’cause-of-cancer’ discussion.
Firstly, let’s look at the cell itself. All cells of the body function and then die and are replaced. The process of cell multiplication/ reduplication entails the splitting of the cells by mechanisms that are mostly of a chemical nature. Sometimes these processes are influenced by external forces, and the physics and chemistry within the cell are compromised. A new and abnormal cell is produced (‘mutant’). This ‘weirdo’ could then begin to grow and multiply much faster than the original cells from which it emerged. These new cells tend to overrun the normal cells.
So we must now turn our attention to those factors/agents that will trigger the formation of the mutants and which will carry the cell multiplication along the aberrant path that finally leads to tissue destruction and eventually the death of the host.
Some examples are:
(i) Ultra-violet rays, X-rays, nuclear radiation
Again, we are dealing here with empirical observation. The actual physico-chemical disturbance in the cell cannot as yet be pinpointed. However, there is enough evidence in humans to show that there is a linkage between radiation (by certain rays – as those mentioned above) and cancer. For example, it is pretty much agreed that an excess of ultra-violet rays on unprotected skin (eg deficient melanin – the colouring material that makes our skin dark) is associated with skin cancer. There is a condition in some dogs called ‘Collie Nose’ (because it affects collies and related breeds especially when they are translocated to sunny climates) which exhibits itself by a skin ulceration on the dog’s nose. Later, the situation becomes real bad and the tissue on the nose becomes cancerous. Similarly, X-rays and nuclear radiation have been implicated in, for example, thyroid cancer and leukaemia respectively.
(ii) Chemicals
Well, I don’t suppose I need to ‘prove’ that chemicals can be main culprits in wrecking the normal cell biology. Lung and skin tissue damage caused by nicotine and coal tar is no longer a theory (although the cigarette manufactures want us to believe differently). Anyway, dogs don’t smoke, so nicotine and coal tars are not on the vets’ hitlist. On the other hand, our companion animals are forced into contact with a barrage of other chemicals – the anti-tick and flea medications (eg the ‘blue spray’), the old engine oils, the Jeyes Fluid, the array of damaging mange ‘remedies,’ etc. And I have not begun to mention the animals’ confrontation with willfully thrown acids, bleaches and the like – all of which may possibly be connected with the creation of monstrous cancer-like skin lesions. Lastly, another example of a chemical causing cancer would be the aniline dye which is linked with cancer of the bladder.
(iii) Mechanical trauma
I mention this tongue-in-check. But how often have we not heard that a blow (inflicted years ago) is the cause, much later on, of a tumour in the area where the blow was struck. I am not getting into this debate, out of respect for my centenarian (now deceased) mother who was a firm believer in the nexus between prior injury and cancer, and who could have out-argued me any day of the year.
(iv) Viruses
When I was at vet school (it seems like that was a thousand years ago), the virus theory of cancer was in full swing. The other day when I was participating at one of my annual ‘refresher’ courses, I could not help being amused at the way the pro-virus argument for the cause of cancer seems to have reached the dustbin of medical history. Yet, let it be clear, viruses have been known to experimentally cause cancer in lab animals. Furthermore, warts and oral papillomas in dogs and cats are definitely associated with viruses.
(v) Parasites
I write this only because I can remember reading somewhere that certain parasitic infections are associated with cancer of the bladder in the dog.
Next week we’ll have a look at various types of tumours.
Please implement disease preventative measures (vaccinations, routine dewormings, monthly anti-heartworm medication, etc) and adopt-a-pet from the GSPCA’s Animal Clinic and Shelter at Robb Street and Orange Walk, if you have the wherewithal to care well for the animals. Do not stray your unwanted pets, take them to the GSPCA’s Clinic and Shelter instead. If you see anyone being cruel to an animal, or if you need any technical information, please get in touch with the Clinic and Shelter by calling 226-4237.
