Pets and MS, is there a link?

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Over the years I have been asked about just about everything and anything that can cause MS. But, this is a new one on me.

Do pets cause MS? Specifically, is childhood pet ownership or exposure linked to the development of MS.

The concept is not as far fetched as it may initially appear. For instance, early on there were concerns over canine viruses causing MS. Pet ownership is common in the developed world and may be an association, and losing a pet can be a very stressful event and their is a link with acute stressful events.

Therefore, the authors in this publication have searched for studies that have specifically looked at this. They found 26 studies ranging from 1965-2019. But there are a few issues to consider. For instance, the diagnosis of MS has changed significantly over this period ranging from primarily history and examination and later following a specified criteria, be it Poser or the McDonald criteria. Also, the exposure period to pets vary between the studies. But, for the purposes of this analysis, the authors only looked at those that fit their definition of ‘childhood exposure’.

Pets studied varied from dogs, cats, birds, rabbits, horses, and guinea pigs. The forest plots can be found below (the further to the right the greater the likelihood; top-bottom overall pet ownership, dog ownership, cat ownership, bird ownership, rabbit ownership, horse ownership and guinea pig ownership).

But, overall the authors felt that the studies were to varied to form any definite conclusions, and advice caution on making recommendations for or against pet ownership based on their findings.

Figure: Forest plots from meta-analysis showing (top to bottom): overall pet ownership, dog ownership, cat ownership, bird ownership, rabbit ownership, horse ownership and guinea pig ownership.

Abstract

Mult Scler Relat Disord. 2021 May 25;53:103046. doi: 10.1016/j.msard.2021.103046. Online ahead of print.

Childhood pet ownership and multiple sclerosis: A systematic review and meta-analysis

Laura Edwards Christopher Tench

Background: Many studies have been conducted investigating a range of environmental factors which have been implicated in the pathogenesis of multiple sclerosis (MS). We collated available data about exposure to domestic animals before symptom onset in MS to perform a systematic review and meta-analysis.

Methods: Medline, Embase and Cinahl were searched for relevant articles, based on pre-defined inclusion and exclusion criteria and reference lists were hand-searched. Data were extracted and critical analysis was conducted using the Newcastle-Ottawa criteria. Meta-analysis used random effects.

Results: Study heterogeneity was high and study quality was variable. Random effects meta-analysis showed no associations with any pet ownership and development of MS.

Conclusion: It is not possible to draw definitive conclusions from this work. The studies included had a high level of heterogeneity. There are many variables involved in pet ownership and exposure and the nature of the way these have been studied makes the analysis challenging.

About the author

Neuro Doc Gnanapavan

20 comments

  • Different types of stresses very rarely gets talked about in MS and it’s a factors of every day life, maybe though childhood also. I.e losing a pet.

    Maybe stress on the body is not easily understood that’s why people shy away from it, do clinicians even know what stress does to our system?

    From my experience if you even mention to a doctors you’ve been stressed lately, they change the subject. It’s like it’s avoided.

      • Very interesting and pretty worrying.

        The one this about the healthcare system is it mainly focuses on symptoms and not the causes of illness

        Stress just seams like a mystery that’s not understood and therefore commonly ignored to me.

        The chemicals created in stress responses could be at cause of malfunctioning immune systems who knows. But it’s a factor of life that some people naturally don’t handle aswell as others.

        It’s an environmental factor that’s seams to get over looked and is abit of an elephant in the room.

  • You need to allow for confounders in a study of this kind. The pretty Forest Plots look like somebody has taken a course in EBM without really understanding the tool and they aren’t appropriate where there is study heterogeneity.

    • Yes of course, and this one of the major problems with meta analyses. But they considered to high grade of evidence which is altogether questionable.

      • This isn’t a problem with Forest Plots. As Doug Altman told me, if the studies are heterogenous, don’t do a meta-analysis. It’s like representing skewed data with an arithmetic mean. It’s meaningless and if an article appears with this error, the editor and Journal are meaningless too.

        • Doug Altman would know! But, to be fair the authors do point this out. Maybe the MS databases can look at this (they’re now large enough), taking into account recall bias etc. More than likely, however, it would be waste of everyone’s time.

  • This study seems to be bullpoop rubbish. How could you possibly even start to compare? They used quite a variance of pets… Not all even canine. And of course they forgot my silky, slinky, bed cover stealing snakedog baby who is actually a ferret but thinks he’s my boss & what’s his is his and what’s mine is his. Ferrets are very similar in the viruses we catch, including some coronaviruses😔. But what they may want to consider studying if they are going to study links with MS to pets is the chemicals used in/on pets… These flea spot drops, and the Capstar pill… Literally the pill kills fleas within 30 minutes by acting on the central nervous system within the flea. Seriously?!! What is that doing to the poor kitty or doggie ingesting that pill? And then they pee that out into the ground,.. etc..
    Feel free to look up this neurotoxic chemical Nitenpyram

    • Ferrets would definitely be considered far from the median pet ownership with n=1 (yourself) currently as the only data point so far 😉
      Chemicals are a valid consideration cf. farming chemicals in Parkinson’s.

      • Far from the median Pet ownership….Tell that to a Yorkshire man where they are coming out of their trousers:-)

    • Well said. When my childhood cats were rescued from being dumped in the river Holme they were flea infested. The health visitor who rescued them covered them in anti flea powder, to the point that they couldn’t stand up. 19 and 23 years later they died. I suspect chronic exposure to flea treatments isn’t good, but it did my cats no harm in the long run.

    • 😂😂😂 I’m glad you had fun reading my comment. Although I meant it to be serious (no such thing in my life), it was quite comical. N=1 (yourself)… I’m still giggling..
      I guess I may have to change my name to something else befitting of a ferret owner.

    • Queen bee, great point about chemicals we put on or in pets! I’ve wondered much about this myself. And I do absolute minimum acceptable per vet. What about the live vaccines we give pets, such as bordeatella for kennel cough? My dog is lovely but slobbery and so an intranasal live vaccine for her was potentially dangerous for me as immune compromised. I arrange ahead of time for vet to get non live version of bordetella vaccine. But I was surprised neither my vet nor doctors had it on their radar. Is it really so rare or low risk to immune compromised? Link to live pet vaccine discussion https://www.wormsandgermsblog.com/2017/04/articles/animals/dogs/modified-live-vaccines-pets-and-immunocompromised-owners/

      My vet then cautioned me to ensure I gave dog dewormer regularly because he felt worms were potentially dangerous in my immune compromised state. Could exposure to animal parasites increase chance of MS?

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