2026-04-29 ブリティッシュコロンビア大学（UBC）
＜関連情報＞
- https://news.ubc.ca/2026/04/outdoor-cats-carry-infectious-diseases/
- https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014160
飼い猫の屋外放し飼いは人獣共通感染症病原体への曝露リスクを高める：世界的な総合的研究 Outdoor roaming of owned cats elevates risk of zoonotic pathogen exposure: A global synthesis
Amy G. Wilson ,Scott Wilson,Peter P. Marra,David R. Lapen
PLOS Pathogens Published: April 20, 2026
DOI:https://doi.org/10.1371/journal.ppat.1014160
Abstract
Domestic animals play a central role in pathogen transmission at the human–wildlife interface. Domestic cats, in particular, are uniquely consequential in disease spillover dynamics due to their global distribution, large, human-subsidized free-roaming populations, and high contact rate with humans, domestic animals, and wildlife. However, the extent to which human ownership and management mitigate this spillover risk remains a key knowledge gap. To address this gap, we conducted a global systematic review and quantitative synthesis of the prevalence and diversity of zoonotic pathogens in indoor-only, outdoor-owned (roaming unsupervised), and unowned (feral or stray) cats. Our dataset comprised 174,064 individuals from 88 countries, representing 124 pathogen species, 97 of which are zoonotic. Using generalized linear models within a Bayesian framework and rarefaction analyses, we show that ownership provides limited protection against zoonoses when owned cats have unsupervised outdoor access. Outdoor-owned cats were 3–5 times more likely to carry zoonotic pathogens than indoor-only cats, and, notably, had infection odds statistically equivalent to those of feral cats, despite receiving presumed veterinary care and feeding. Feral cats carried the highest pathogen diversity, however, outdoor-owned cats still harbour 1.5 times the helminth richness of indoor cats, highlighting their potential as effective bridges for pathogen spillover. With approximately 62% of owned cats roaming freely worldwide, and rates exceeding 90% in some regions, these findings reveal a major yet overlooked route of zoonotic risk. Public health and One Health frameworks have traditionally focused on feral cats; however, our results highlight the need to explicitly incorporate owned outdoor cats into zoonotic disease prevention strategies by restricting unsupervised roaming and promoting responsible ownership practices. Without such integration, current frameworks risk overlooking a pervasive and preventable pathway for pathogen transmission at the human–wildlife–domestic animal interface.
Author summary
Cats are among the most common companion animals worldwide and are often allowed to roam freely outdoors, bringing them into close contact with people, other domestic animals, and wildlife. While these interactions raise well-known conservation concerns, they also expose cats to a wide range of pathogens. Disease risk is commonly associated with feral cats, but the relative risk for owned cats allowed to roam outdoors unsupervised has remained unclear. To address this question, we compiled data from studies conducted globally, encompassing a broad range of pathogens relevant to human health. We found that cats with outdoor access were more likely to carry infections than indoor-only ats, and that their risk of infection was comparable to that of feral cats. This similarity suggests that outdoor access leading to hunting or contact with wildlife and other free-roaming animals can rapidly negate the protective effects of ownership. Because owned cats also have frequent close contact with people, infection acquired outdoors may increase opportunities for onward exposure to owners and the broader public, including through environmental contamination. Together, these results show that how people manage their pets plays a major role in shaping disease transmission between wildlife, domestic animals, and humans, highlighting that strategies designed to reduce the ecological impacts of free-roaming cats can simultaneously deliver substantial benefits for both public health and biodiversity.
