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.
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
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.