A Bay Area dog named Bubba died from leptospirosis in late 2025. Two more dogs tested positive near a Berkeley encampment by January. In Los Angeles, at least six dogs have contracted lepto since the start of 2026. And spring rain season is just getting started.

If your dog drinks from puddles, creek crossings, or standing water on trail — and let’s be honest, most hiking dogs do — leptospirosis should be on your radar right now.

Quick Overview: Leptospirosis Risk for Hiking Dogs

Detail	Info
What it is	Bacterial infection spread through contaminated water and soil
Peak risk	March through May (spring rain + snowmelt)
How dogs get it	Drinking or wading through puddles, creeks, standing water
Current outbreaks	Berkeley (2+ dogs), Los Angeles (6+ dogs since January 2026)
Vaccine status	Now recommended as core (annual) by AAHA/AVMA expert panels
Fatality if untreated	Up to 20-30% in severe cases
Treatable?	Yes, with early antibiotics. Late diagnosis is dangerous

Bottom line: Lepto is a real and growing threat to trail dogs this spring. Get your dog vaccinated annually, avoid stagnant water on trail, and know the early symptoms.

What Leptospirosis Actually Does to Dogs

Leptospirosis is a bacterial infection caused by Leptospira spirochetes. The bacteria live in the urine of infected animals — rats, raccoons, skunks, deer, livestock — and survive for weeks in warm, wet environments. Standing water, muddy puddles, slow-moving creeks, and flooded trail sections are exactly where the bacteria thrive.

Your dog doesn’t need to drink contaminated water to get infected. Wading through a puddle with a small paw abrasion is enough. The bacteria enter through mucous membranes or broken skin, spread through the bloodstream, and attack the kidneys and liver.

Early symptoms look like a dozen other things: lethargy, loss of appetite, vomiting, fever. By the time kidney failure or jaundice shows up, treatment gets complicated and survival rates drop. A dog that seemed fine after a Saturday hike can be critically ill by Tuesday.

That’s what makes lepto dangerous for trail dogs specifically. The exposure happens in exactly the places we take our dogs, and the early warning signs are easy to dismiss as “tired from a big day.”

Why Spring 2026 Is a Heightened Risk

Three factors are converging right now.

California outbreaks are active. The Berkeley cases were linked to rat populations near an encampment, but the bacteria don’t stay in one ZIP code. Infected wildlife moves. Contaminated runoff spreads. Berkeleyside reported that leptospirosis was detected in rats for the first time in five years in Alameda County. In LA, the NBC Los Angeles coverage noted six-plus dog cases since January, with vets warning the numbers will climb as temperatures rise.

Spring rain and snowmelt create perfect conditions. Lepto bacteria survive in standing water for 30 days or longer. March through May brings exactly the conditions that concentrate bacteria: rain fills low spots on trails, snowmelt feeds creeks and puddles, and temperatures climb into the range where Leptospira thrives. Every muddy trailhead puddle and every slow creek crossing becomes a potential exposure point.

More dogs are hitting trails after winter. Spring is when trail traffic spikes. Dogs that spent winter on neighborhood walks are suddenly splashing through seasonal creeks and drinking from water sources they haven’t touched in months. Rocky practically sprints for the first puddle he sees after a long winter. I get it. But that enthusiasm is exactly the problem.

The Vaccine Situation Has Changed

Here’s the most actionable piece of this entire post: the leptospirosis vaccine is now considered a core vaccine for all dogs.

The 2022 AAHA Canine Vaccination Guidelines were updated in 2024 to reclassify lepto from “non-core” (meaning risk-based, optional) to “core” (meaning recommended for all dogs). An expert panel now recommends annual vaccination rather than every three years, because immunity wanes faster with lepto than with diseases like distemper or parvo.

If your dog isn’t vaccinated for lepto, the initial series is two shots spaced two to four weeks apart, followed by annual boosters. Protection kicks in about two weeks after the second dose.

For hiking dogs specifically, here’s the timing that matters: if you’re planning spring trail trips starting in mid-March, you needed the first shot in mid-February to be fully protected by now. If you haven’t started, get the first dose this week. You’ll have partial protection within two weeks and full protection about a month out.

Rocky has been on annual lepto boosters since I started taking trail vaccinations seriously two years ago. It’s one shot per year, about $25-40 at most vets, and it’s the single cheapest insurance policy for a dog that spends time near water on trail.

What About Side Effects?

The lepto vaccine has a slightly higher reaction rate than some other canine vaccines. Most reactions are mild: soreness at the injection site, low energy for a day, maybe a slight fever. Serious reactions are rare. The older four-serovar vaccines had more issues; the newer formulations are better tolerated.

Talk to your vet about your dog’s specific history. But for a dog that regularly encounters standing water, creek crossings, and wildlife corridors on trail? The risk calculus is straightforward.

Trail Prevention: What to Do Beyond the Vaccine

Vaccination is your foundation. But it doesn’t cover all Leptospira serovars, and no vaccine is 100%. Layer these habits on top.

Manage Water Sources on Trail

• Carry your own water and a collapsible bowl. Don’t rely on natural water sources, especially standing water. If you need gear recommendations, the best dog first aid kits for hiking post covers hydration supplies as part of your trail kit.
• Redirect your dog from stagnant puddles. Moving water is lower risk than standing water, but neither is guaranteed safe. Puddles in low-lying areas near wildlife corridors are the highest-risk water sources.
• Avoid flooded or recently flooded trail sections. If a trail section looks like it’s been underwater recently and the mud is still saturated, route around it.

Know the High-Risk Terrain

Lepto risk is highest where water collects and wildlife concentrates:

• Creek crossings with slow or standing water (not fast-moving mountain streams)
• Puddles on fire roads and wide trails where runoff pools
• Meadow edges and wetland margins where deer, raccoons, and rodents drink
• Trailhead parking areas where standing water collects near wildlife crossings
• Urban-adjacent trails where rat and raccoon populations are dense

If you’re already thinking about spring mud season hiking preparation, add lepto awareness to your seasonal checklist. Mud season and lepto season overlap almost perfectly.

Post-Hike Routine

• Rinse your dog’s paws and belly after every hike through wet terrain. Warm water, basic rinse. You’re removing potential bacteria before they find a way in through a micro-abrasion.
• Check for cuts, scrapes, and cracked pads. Open wounds dramatically increase lepto risk. If your dog has a fresh cut and walked through standing water, monitor closely for the next 7-14 days. Dog boots aren’t just for snow — they protect against exactly this kind of exposure.
• Watch for early symptoms for two weeks after any hike near standing water. Lethargy, decreased appetite, increased thirst, vomiting, or fever within 2-14 days of a hike warrants a vet call. Mention the water exposure specifically.

Recognizing Leptospirosis: The Symptom Timeline

Lepto symptoms appear anywhere from 2 to 14 days after exposure. Here’s what to watch for:

Days 1-3 post-exposure: No symptoms. The bacteria are spreading through the bloodstream. Your dog seems completely normal.

Days 4-7: Early signs often look like “off day” symptoms. Decreased energy, reluctance to eat, mild fever, muscle stiffness. Easy to write off as post-hike soreness, especially after a big trail day.

Days 7-14: If the infection progresses, symptoms escalate. Vomiting, diarrhea, increased thirst and urination (as kidneys struggle), yellowing of the gums or whites of the eyes (jaundice, indicating liver involvement). At this stage, get to a vet immediately.

The critical mistake: Most owners who lose dogs to lepto waited too long because early symptoms looked like normal post-adventure fatigue. If your dog was near standing water on a recent hike and seems “off” four to seven days later, don’t wait. A simple blood test and urine test can catch lepto early, and early antibiotic treatment has a high success rate.

When to Call Your Vet (Featured Checklist)

Call your vet if your dog shows ANY of these within 2 weeks of hiking near water:

• Sudden loss of appetite lasting more than 24 hours
• Vomiting or diarrhea with no obvious dietary cause
• Lethargy beyond normal post-hike tiredness
• Increased drinking and urination
• Yellowing of gums, eyes, or skin
• Muscle stiffness or reluctance to move
• Fever (normal dog temp is 101-102.5F)

Lepto Is Also a Human Health Risk

One more reason to take this seriously: leptospirosis is zoonotic. Dogs can transmit it to humans through urine, and the bacteria can survive on surfaces and in soil. If your dog contracts lepto, you’re at risk too.

San Francisco has already reported a human case in 2026. LA County has reported fewer than five. These numbers are small, but the ABC7 coverage of Bubba’s story specifically flagged the human transmission risk.

For hikers who share a tent with their dog on overnight trips, this matters. If your dog waded through contaminated water and then sleeps in your tent, their wet fur and paws are potential vectors. Another reason the post-hike rinse routine is worth the two minutes it takes.

The Spring Trail Checklist for Lepto Prevention

Here’s the practical takeaway. Print this or screenshot it before your next spring hike.

1. Confirm your dog’s lepto vaccination is current. Annual boosters. If unvaccinated, start the two-dose series now.
2. Pack your own water supply. Don’t let your dog drink from puddles or slow-moving water sources. A collapsible bowl and an extra liter of water weighs almost nothing.
3. Route around standing water when possible. If a trail section is flooded or puddled, go around.
4. Protect open wounds. If your dog has a cut or cracked pad, consider boots or skip the creek crossing entirely. See the tick prevention guide for more on managing spring-specific hazards.
5. Rinse paws and belly after every wet hike. Basic hygiene, big payoff.
6. Know the symptom window. Watch for lethargy, vomiting, or appetite loss 2-14 days post-hike. Don’t assume it’s just tiredness.
7. Tell your vet about water exposure. If your dog gets sick after a hike, mention the standing water. It changes the diagnostic approach.

Lepto isn’t new, but it’s having a moment. California is seeing cases climb, vaccination guidelines have shifted, and spring is the highest-risk season. The dogs most exposed are the ones doing exactly what we do: hitting trails, crossing creeks, splashing through mud.

Rocky’s vaccinated, I carry water for both of us, and I’ve started being pickier about which creek crossings I let him wade through. It takes almost no extra effort. The alternative — catching it late and hoping antibiotics work fast enough — isn’t a trade I’m willing to make.

Get the shot. Carry the water. Watch for the signs. Spring trails are waiting.