In a previous letter to Moose Jaw Today Mr. Richard Dowson confidently asserted that canine distemper virus (CDV) is the cause of multiple sclerosis (MS). His latest letter (Jan 20) offers no new data or arguments.
The study I mentioned in my brief response to his first letter stated that there is an association between Epstein Barr virus (EBV) and MS. It did not make a categorical statement about proving the cause of MS, nor should it have done so. That would have been irresponsible science.
We are (again) informed by Mr. Dowson that CDV was found in 100% of a study population with Paget’s disease. This proves that… 100% of the people studied had Paget’s disease and that CDV material was found in the bony lesions. Interesting, but irrelevant as far as the etiology of MS is concerned.
Mr. Dowson tells us, quite correctly, that EBV is one of the most common viruses found, but it needs to be pointed out that not everyone who meets up with EBV will get infectious mononucleosis, have a weakened immune system or any of the host of other diseases associated with this virus.
We are also told that “There seems to be no evidence that EBV causes demyelination”
This statement is incorrect. In the link I gave to the EBV/MS study, we read the following: “Serum levels of neurofilament light chain, a biomarker of neuroaxonal degeneration, increased only after EBV seroconversion.”
We are also informed that EBV …weakens the Immune System. The ‘sick’ person can’t effectively fight infections. If a Pathogen is present, it could infect the person, thus EBV ‘plays a role’.
And also: ”Does this mean because EBV reduced the immune system’s ability to fight infections and a ‘predator virus’ invaded the individual while he or she was ill?”
If I understand Mr. Dowson correctly, he asserts that EBV may cause CDV infection leading to MS. In order to prove this hypothetical conjecture one would need, at the very least, data on the relationship (if any) between serial infections of EBV and CDV in the same host. No such data exist, to the best of my knowledge.
In Mr. Dowson’s previous letter he stated: “The Netherlands has almost no cases of Multiple Sclerosis – about 1 case in 100,000 population”
This is not even nearly correct – the actual incidence is 88 times higher. See reference (1).
We also read: “Why so low? The Netherlands has strict pet ownership laws”
So does just about every country in the EU.
If CDV causes MS, it is quite reasonable to assume that there should be a relationship between dog ownership and that disease, an opinion Mr. Dowson clearly shares.
One can calculate the number of dogs/100 000 population in EU countries (1, 2) and compare that to the prevalence of MS in those countries. Here are the results for some member states of the EU.
Germany: 12891 dogs/100 000; Prevalence of MS: 140/100 000.
Netherlands: 11470 dogs/100 000; Prevalence of MS: 88/100 000.
UK: 12686 dogs/100 000; Prevalence of MS: 164/100 000.
Italy: 13833 dogs/100 000; Prevalence of MS: 113/100 000.
France: 11538 dogs/100 000; Prevalence of MS: 95/100 000.
Denmark: 10649 dogs/100 000; Prevalence of MS: 227/100 000.
Even a superficial examination will show that there is no correlation between dog ownership and prevalence of MS. For example, the difference in dog ownership between Germany and the Netherlands is merely 11%, while MS prevalence differs by 37%.
The UK and the Netherlands differ by 9.5% with regard to dog ownership, but a whopping 86% in the prevalence of MS.
It is of course possible that CDV does indeed play a role in the etiology of MS, but so far Mr. Dowson has offered no convincing data or argument in favour of that hypothesis. The plural of anecdote isn’t data.
One must also bear in mind that various other viruses have been implicated in this regard (4,5).
Vaccination against canine distemper have become widespread over the last few decades, so much so that a veterinary surgeon in Ontario has not seen a case for 32 years (5). This by itself argues against CDV as a cause of MS.
If Mr. Dowson is so convinced that his proposition is correct, I suggest that he writes it up as a scientific article and submit it to a medical journal of note.
Leon W. Retief
I must apologize to Mr. Dowson and readers for two typos in my previous letter. The links to references (2) and (5) contain spaces before the URLs which make them inoperable.
Here are the correct URLs: