Association between exposure to farm animals and pets and risk of Multiple Sclerosis

•Inconsistent evidence exists regarding the association between exposure to pets and/or other animals and MS risk.•Our group recently showed that farming and exposure to livestock increased the risk of demyelination.•In this study, farming, exposure to livestock or specific farm animals were not associated with MS.

PurposeThere exists inconsistent evidence regarding animals including pets as risk factors for the development of Multiple Sclerosis (MS). We investigated the association between farm animals and pets as possible environmental factors in MS development.MethodsPopulation based case-control study with 136 clinically definite MS cases and 272 controls randomly chosen from the community matched on sex and age. Data was collected from both questionnaire and a lifetime calendar detailing residence, occupation and pet/animal exposure over the course of participant's lives.ResultsExposure to farming, livestock, specific farm animals and remoteness of residence showed no significant association with MS risk. Exposure to cats prior to disease onset was associated with a greater risk of MS (Adjusted Odds Ratio 2.46 (1.17–5.18)) but without a clear dose-response (test for trend, p=0.76).ConclusionsIn contrast to other literature, farming and exposure to farm animals were not associated with MS. While we identified an association between cat exposure and MS, there was no dose-response relationship, and previous studies showed inconsistent results, leaving us to conclude that there is no strong evidence that exposure to cats is associated with MS.