Bringing leptospirosis back to the basics

Leptospirosis has shed its old reputation as a disease that only affects big dogs that spend their lives outdoors. In this episode of The Vet Blast Podcast presented by dvm360, host Adam Christman, DVM, MBA, chief veterinary officer at Fetch dvm360, gets back to basics on leptospirosis with Robert Armentano, DVM, DACVIM (SAIM), head of the internal medicine department at Veterinary Specialty Center in Bannockburn, Illinois.

From outdated assumptions about which dogs need the vaccine to the belief that a negative snap test rules out infection, Armentano walks through where the profession's thinking on leptospirosis has fallen behind the science, and what still needs to change.

Below is a partial transcript, edited lightly for clarity.

Adam Christman, DVM, MBA: The epidemiology of leptospirosis has changed over the past 10 years or so. What does that look like, and why do you think that is?

Robert Armentano, DVM, DACVIM (SAIM): For a long time, it was, ‘Oh, the big dogs that are out in the wilderness hunting, let’s just vaccinate them.’ There was a stigma about vaccinating the tiny dogs for lepto. Manufacturers have done a really good job modifying the vaccine, so now it’s becoming more common in the small dogs, and we’re vaccinating them better. If you look at a map, the Midwest is unfortunately one of the hottest hotspots, but there are about 250 serovars across the world. It’s a worldwide disease. We see a ton in the city because of our rodent friends, and out in suburbia, dogs get it from possums and voles carrying the organism.

Christman: Walk us through vaccination. I know the American Animal Hospital Association changed its guidelines to make this a core vaccine. What about pet owners who are hesitant to vaccinate their dogs against lepto?

Armentano: For us, it’s moderately non-negotiable, because for the most part, you could make an argument 20 years ago that the smaller dogs were having more vaccine reactions. We just don’t see that anymore. I can’t remember the last time I’ve seen an actual lepto vaccine reaction that was really compromising to the patient. They’re going to die of the disease long before they die of the vaccine. In an area like ours, it really is a true core vaccine, and I agree with AAHA’s recommendations, especially because of the zoonosis and the chronic carrier stages. It’s not just about their dog. It’s a little bit about global health too, considering we see it across the world.

Christman: If a dog does get lepto, when do you vaccinate them again?

Armentano: There have been 2 big consensus statements looking into this. The old one said the one good thing about a dog getting lepto is that it just got a free vaccine for a year. That has changed, because the argument now is that the dog was only exposed to one serovar, so what about all the others? For the most part, once they’re clinically normal for about a month, we recommend boostering them with the 4-serovar vaccine to cover the rest. You know you’re in an endemic region, and you’re going to get some cross-reactivity, but you want to cover them.

Christman: As we wrap up, are there any misconceptions you think our profession has about leptospirosis? Is there a myth out there, or something you think we could do better with, like the instinct to refer a lepto suspect out right away?

Armentano: For the most part, there isn’t any magic here. I don’t give up on these dogs very easily. The times we’re truly in trouble are when they’re anuric. That’s when we need the bigger therapies. But most of the time, for an acute kidney injury, it’s supportive: keeping them hydrated, giving antibiotic therapy, and trying to clear the infection.

The other misleading part is we see it all the time: ‘Oh, we snapped them, they’re negative. Their MAT was negative. They don’t have lepto.’ That’s not even a little bit true. We have to do the convalescent testing and prove there’s a positive PCR test. There’s more criteria we need than just running one single test and being done.

The last thing I find interesting is that, although we’re not seeing a ton of it in the United States yet, just like every bug out there, we’re starting to see a little more resistance to the organism. There are some interesting studies out of South America where dogs were treated with doxycycline, and 2 weeks later they were clinically better but still urine PCR-positive, meaning they were still shedding the organism. So if a dog was PCR-positive to begin with, I strongly recommend retesting at the end of treatment to make sure they’ve gone PCR-negative. We owe that to the other dog in the house, the dog next door, and the other family members.