Association between exposure to farm animals and pets and risk of Multiple Sclerosis
Introduction
Multiple Sclerosis (MS) is a complex disease of the central nervous system, and aetiological factors continue to be uncovered (Pakpoor and Ramagopalan, 2014). Contagious viral illnesses of pets, such as canine distemper, may potentially be associated with an increased risk of MS. However, immune modulation as a result of exposure to pets could also have a beneficial effect, in line with the “hygiene hypothesis”, which proposes that early life infections may down-regulate allergic and autoimmune disorders (Bach, 2001). Inconsistent evidence exists regarding the association between exposure to pets and/or other animals and MS risk (Ghadirian et al., 2001, Bansil et al., 1997, Alonso et al., 2011), but our group recently identified a positive association between farming and exposure to livestock and risk of central nervous system demyelination (Valery et al., 2013). In a population based case-control study in Tasmania, we examined whether farming, and exposure to pets and farm animals prior to the onset of MS was associated with MS risk.
Section snippets
Study participants
The population is described in greater detail elsewhere (van der Mei et al., 2003, Ponsonby et al., 2005). People with MS under the age of 60 years were recruited in the state of Tasmania through the use of advertising, information evenings and letters from neurologists. In total, 169 subjects volunteered to participate, while 136 cases were included in the final sample. Thirty (17.8%) did not meet the study protocol with regard to the diagnosis of MS, one person refused a neurological
Results
Overall, 68% of participants were female, and the mean time since diagnosis of the cases was 9.4 years (Table 1). Table 2 shows the association between exposure to various animals and MS. In relation to farm-related variables, no associations were found for being a farmer (only two controls were farmers and no cases), living on a farm, exposure to specific farm animals (cows, sheep, horses, pigs, poultry, goats, sheep dogs, native animals or ferrets), or a variable that combined the individual
Discussion
This population-based case-control study investigated whether farming and exposure to various pets or farm animals influenced the risk of MS. No associations were observed for farming, exposure to farm animals or remoteness of residence. We observed that people with MS were more likely to have had exposure to cats before diagnosis (OR 2.46 (1.17–5.18)), but there was no dose-response association with duration of exposure to cats, leaving it doubtful whether this was a true association. If there
Conflict of interest
There are no relevant conflicts of interest to declare.
Funding
This project was supported with funding from the National Health and Medical Research Council (NHMRC) of Australia (ID 106928), the Australian Rotary Health Research Fund, and MS Australia. IvdM is supported by an ARC Future Fellowship.
Acknowledgements
We thank the participants, Trish Groom and Jane Pittaway for conducting the environmental interviews, Ceri Flowers for the genetic fieldwork, Natasha Newton for administrative support and data entry, Sue Sawbridge and Tim Albion for the development and management of the database, Andrea Polanowski for the genotyping, the Tasmanian Multiple Sclerosis Society for assisting with the recruitment of volunteers, and Trevor Kilpatrick, H. Butzkueven, A. Hughes, B. Drulovis, and S. Siejka who were
References (15)
Protective role of infections and vaccinations on autoimmune diseases
J. Autoimmun.
(2001)- et al.
A case-control study of risk factors for Multiple Sclerosis in Iran
Mult. Scler.
(2011) - et al.
Multiple Sclerosis in India: a case-control study of environmental exposures
Acta Neurol. Scand.
(1997) - et al.
Environmental factors in early childhood are associated with Multiple Sclerosis: a case-control study
BMC Neurol.
(2011) - et al.
Further evidence of a possible association between house dogs and multiple sclerosis
Ann. Neurol.
(1978) - et al.
A case-control study of the association between socio-demographic, lifestyle and medical history factors and multiple sclerosis
Can. J. Public Health = Rev. Can. De. Sante Publique
(2001) - et al.
Environmental exposures and the risk of multiple sclerosis investigated in a norwegian case-control study
BMC Neurol.
(2014)
Cited by (9)
Childhood pet ownership and multiple sclerosis: A systematic review and meta-analysis
2021, Multiple Sclerosis and Related DisordersCitation Excerpt :Definition of exposure: there was wide variation in definition of periods and nature of exposure, not only between studies but also in some cases within studies, when looking at cases and controls. While one of the exclusion criteria was for studies that included current pet ownership for cases, some studies compared prior pet ownership for cases with pet ownership at any time (i.e. up to and including the study period) for controls (Flodin, Soderfeldt et al. 1988, Alonso, Cook et al. 2011), while others deliberately matched controls to cases and took the case age of onset as a “cut-off” for the control exposure (Antonovsky, Leibowitz et al. 1965, Alter and Speer 1968, Antonovsky, Leibowitz et al. 1968, Cook, Dowling et al. 1978, N. Koch-Henriksen 1989a, Operskalski, Visscher et al. 1989, Landtblom, Flodin et al. 1993, Siejka, Taylor et al. 2016). Furthermore, there was little consistency between ages of exposure to the animals, with studies ranging from at any time before disease onset, to specific narrow age ranges, to “childhood” / before age 15, age 19; specifically in the 1 year period prior to symptom onset.
Animal exposure over the life-course and risk of multiple sclerosis: A case-control study within two cohorts of US women
2019, Multiple Sclerosis and Related DisordersCitation Excerpt :Furthermore, it has been proposed that exposure to animals (kept as pets) may influence the risk of MS. For instance, exposure to animals who are prone to demyelinating diseases (e.g. German Shepherds) might be associated with an increased risk of MS (Clemmons, 1992; Lincoln et al., 2008). Despite previous efforts, studies have shown conflicting results (Cook and Dowling, 1977; Jotkowitz, 1977; Cook et al., 1978; Read et al., 1982; Norman et al., 1983; Anderson et al., 1984; Flodin et al., 1988; Operskalski et al., 1989; Landtblom et al., 1993; Bansil et al., 1997; Ghadirian et al., 2001; Hernán et al., 2001; Alonso et al., 2011; Conradi et al., 2011; Gustavsen et al., 2014; Siejka et al., 2016). Several studies have shown that people living with MS were more often exposed to animals in the years before the onset compared to healthy controls or controls with other neurological diseases (Cook and Dowling, 1977; Jotkowitz, 1977; Cook et al., 1978; Flodin et al., 1988; Landtblom et al., 1993; Bansil et al., 1997; Hernán et al., 2001; Siejka et al., 2016).
Editors’ Welcome
2016, Multiple Sclerosis and Related DisordersIncreased frequency of canine distemper virus-specific antibodies in multiple sclerosis
2021, Brain and BehaviorSeroprevalence of anti-Toxocara antibody among multiple sclerosis patients: a case–control study
2020, Journal of Parasitic Diseases