What happened
- A UC Davis study, reported in May 2026, examined a leptospirosis outbreak in Los Angeles County in 2021 that sickened more than 200 dogs 1,2.
- The researchers concluded that gaps in vaccination and in infection control, including crowded boarding settings, contributed to the outbreak 1,2.
- The researchers said major veterinary organizations now recommend annual leptospirosis vaccination for all dogs, and that the infection is expected to become more common with climate change 2.
Why it matters
Leptospirosis is a bacterial infection that can seriously affect dogs, and it can spread to people. Whether the vaccine is advised for your dog depends on local risk and lifestyle, and the recommendation varies by organization: the WSAVA guidelines, for example, treat it as a core vaccine where it is common. Our dog health guide explains core and non-core vaccines.
This research is also one of eight discoveries named in the AKC Canine Health Foundation’s 2026 Discovery of the Year shortlist 3 (see our report).
We read this study through news coverage, not the full paper. Ask your veterinarian which vaccines suit your dog.
Sources
- Study: LA canine outbreak caused by low vaccination rates, crowded boarding. HealthDay. Open source
- Dog daycare outbreak exposes gaps in puppy leptospirosis vaccinations. News-Medical. Open source
- Meet the eight discoveries recognized by the 2026 Canine Health Discovery of the Year Award. AKC Canine Health Foundation. Open source