The rain is back, the low spot by the fence is a pond again, and your dog thinks it is a water bowl. Here is what leptospirosis is, why wet months matter, and the handful of things that actually lower the risk.
Leptospirosis is a bacterial infection dogs usually catch from water or soil contaminated with the urine of infected animals, especially rats, raccoons, opossums, and other wildlife. It is regularly diagnosed in Washington dogs, it can cause kidney and liver failure, and it can pass to people. It is treatable with antibiotics when caught early, and the American Animal Hospital Association now recommends the vaccine for most dogs. If your dog seems off after puddle season starts, call your vet.
We will say this up front, because it would be very convenient for a poop company to pretend otherwise: leptospirosis spreads through urine, not poop. None of the health agencies we checked list dog feces as a route. We are writing about it anyway, because the conditions that spread it are exactly the ones we walk through in Pierce County yards every week from October to May, and because there is a real, if indirect, connection to what we do. We will get to that.
Leptospirosis is caused by spiral-shaped bacteria called leptospires. According to the Washington State Department of Health, they thrive in moist environments and in water, and they spread through the urine of infected animals. Carriers include rats, mice, squirrels, raccoons, skunks, opossums, foxes, and deer.1 Rats are described as universal reservoirs.3
Dogs pick it up from lakes, streams, puddles, vegetation, and mud.1 The bacteria get in through the mouth, broken skin, or the lining of the eyes and nose, often from stagnant or slow-moving water.12 Once it is out in the environment, it can survive in water or moist soil for weeks to months.3
Put those facts together and the Pacific Northwest wet season starts to look like a very comfortable place for it: months of saturated lawns, standing water that never quite dries, and wildlife that moves closer to houses as it gets colder.
Yes. Washington's own disease surveillance guidelines say leptospirosis "is regularly diagnosed in dogs in Washington," and veterinarians are required to report animal cases to the Washington State Department of Agriculture.3 2
The most recent public example is on the east side of the state. Spokane Regional Health District reported a confirmed canine case in July 2025, and by May 2026 counted three confirmed canine cases in Spokane County over ten months, with no apparent link between them.4 5 Unlinked cases popping up in different households is a reminder that this is not a one-off outbreak you can avoid by skipping one dog park. It lives in the environment.
We could not find published counts for Pierce County dogs specifically. That is not the same as it not being here. It mostly reflects that animal case numbers are not widely published.
When is the risk highest? Sources frame the season a little differently. Cornell describes the bacteria thriving "especially during late summer and into fall," the AKC Canine Health Foundation points to fall and to water after heavy rains, and the AVMA notes timing varies by region.12 6 14 The common thread is simple: more rain and more standing water mean more chances for exposure.
Early signs are easy to mistake for a stomach bug or a dog that overdid it at the park.
Fever, vomiting, diarrhea, belly pain, refusing food, and severe weakness or depression.1
Stiffness or severe muscle pain, often mistaken for an injury.1
This is not a minor illness. In one Chicago study cited by the AKC Canine Health Foundation, more than a quarter of infected dogs did not survive.6 The Department of Health is clear on the upside, though: leptospirosis is treatable, and early antibiotics improve the odds of recovery.1 That is why "he's just a little off since the weekend" is worth a phone call during the wet months, especially if your dog has been drinking from puddles.
For a long time the lepto vaccine was treated as optional, something for farm dogs and hunting dogs. That changed. In a 2024 update to its canine vaccination guidelines, AAHA moved leptospirosis to the core list, with task force members recommending the vaccine for all dogs "regardless of their size, breed, geographical location, or lifestyle."7
Lepto can pass from dogs to people, but the Department of Health says this does not often happen, and Washington sees only zero to five human cases reported a year.1 2 If your dog is diagnosed, the CDC recommends covering cuts, wearing gloves when cleaning up urine, and disinfecting surfaces with one part household bleach to ten parts water.13 Keep little ones from helping with that particular chore.
The agency advice is short: keep dogs away from standing water, puddles, and ponds, prevent rodent infestations, and vaccinate.1 3 The rest of the list below is our own practical take from spending a lot of time in wet Pierce County backyards.
That last item is the connection we promised. The University of California's pest management program tells homeowners to clean up dog and cat feces specifically because rats will eat it.15 Rats are the main carrier of leptospirosis. So while poop does not spread lepto, a yard full of it is an open invitation to the animals that do. If you end up dealing with rats, read our guide to rat bait and antifreeze safety before anyone puts out poison.
For the bigger picture on what lingers in the yard over the wet months, see dog waste and water quality in Pierce County and our guide to keeping a yard clean through a PNW winter.
The short version: lepto rides in on rodent and wildlife urine and sits in puddles and mud for weeks. Give your dog a better water option than the puddle, take away the things that feed rats, and ask your vet about the vaccine at the next visit. That covers most of what is in your control.
Mostly by contact with water, mud, or soil contaminated with the urine of infected animals such as rats, raccoons, opossums, skunks, and deer. The bacteria enter through the mouth, broken skin, or the eyes and nose, often when a dog drinks from or wades through puddles.
Washington's Department of Health says it is regularly diagnosed in dogs in the state, and animal cases must be reported to the Department of Agriculture. Spokane County confirmed three unlinked canine cases between July 2025 and May 2026. Public counts for Pierce County are not published.
Leptospirosis spreads mainly through urine, not feces. The connection to poop is indirect: rats, the main carrier, will eat dog feces, so a yard with waste left in it can attract the animals that spread lepto.
Fever, vomiting, diarrhea, belly pain, refusing food, weakness, and stiffness or muscle pain. Many dogs also drink and urinate more as the kidneys are affected. Call your vet if these show up, especially during the rainy season.
AAHA now lists the leptospirosis vaccine as core for most dogs, and its task force recommends it regardless of size, breed, location, or lifestyle. Reactions are slightly more likely in small and young dogs but are rare overall. Ask your veterinarian what fits your dog.
It is possible but uncommon. If your dog is diagnosed, cover any cuts, wear gloves when handling urine, wash your hands well, and clean surfaces with a 1 to 10 bleach solution, per CDC guidance.
We are a pet waste and pet care company, not a veterinary practice. This article is general information checked against the sources above. For anything involving your own pet, call your veterinarian.
We cannot drain your lawn, but we can take away one of the things that draws rodents in. Weekly scooping all through the wet season, with a Dooty Report after every visit. Weekly plans are $99/mo (monthly visits start at $49), month-to-month, serving Bonney Lake, Buckley, and nearby Pierce County.
See Scooping Plans → Want the full rainy-season game plan? Read our PNW winter yard guide.