Risk assessment of the exposure of people to methicillin-resistant Staphylococcus aureus (MRSA) from dogs

Abstract

Purpose: The purpose of this study was to assess the risk of exposure of people to MRSA from dogs, via direct and indirect pathways, with special emphasis on companion animal veterinarians. This scenario was used as an example of cross-species spread of antimicrobial resistance genes. Methods & Materials: We conducted a risk assessment to quantify the probability of exposure of people, specifically veterinarians to MRSA. Risk pathways included both direct and indirect (e.g. environment) transmission. A 24h-time period was considered to estimate the probability of potential exposure. Input data was collected through a literature review. When information was not available, expert opinion was considered. Palisade decision tools (@Risk 7.0.1 Pro edition) were used to construct the risk simulation model. The outcome was the probability of exposure within the defined time window. Repeated exposure and exposure load were not considered. Sensitivity analysis was performed to quantify the relative significance of each of the model input parameters. Results: The risk of exposure to MRSA from dogs appears to be low, for individuals with no occupational exposure (2.4x10-8) and one order of magnitude higher for companion animal veterinarians. Most of the available literature focused on reporting cases where similar isolates of MRSA were found in dogs and humans, but there are important data gaps for parameters including exposure load. It is therefore currently not possible to reliably quantify the significance of the different transmission pathways or even to rank them. Conclusion: No significant exposure to MRSA and therefore no indication of related adverse health effects from dog ownership or occupational exposure of small animal veterinarians were identified. However, we only considered a 24h-time period of potential exposure. In a scenario of prolonged colonization of an animal the repeated daily contact will result in cumulative exposure. Also, exposure does not necessarily mean risk. More work is needed to understand the health consequences of exposure to resistance genes, particularly MRSA.