What you need to know about canine leptospirosis right now

sushytska/stock.adobe.com

“Leptospirosis is one of the most exciting reemerging pathogens in the United States.” So began the session, “Three truths and a lie: canine leptospirosis,” presented by Jenifer Chatfield, DVM, DACZM, DACVPM, at the 2024 AVMA Convention in Austin, Texas.¹

Firstly, Chatfield discussed 3 different canine cases, challenging the audience to determine if these dogs had leptospirosis (lepto). The first, a 6-month-old Yorkshire terrier, presented as slightly dehydrated, and was “going backwards on training,” according to the owners, by urinating in the house. Urine analysis (UA) showed bacteria and protein, so the dog was prescribed amoxicillin trihydrate/clavulanate potassium (Clavamox). A few days later, the owners called saying that symptoms initially resolved, but started up again because they had stopped the Clavamox and now need to start up again. What to do now, Chatfield says?

“When testing for lepto, it is complicated,” warns Chatfield. “One of the points of SNAP tests [quick, convenient, blood tests that can be performed at your veterinarian’s office] is to differentiates between the two immunoglobulins. When doing a titer, you need to know if you are measuring IgG or IgM, because in one of those, you find the face of acute disease or exposure. IgM is the antibody in the face of infectious disease that will spike quickly and fall off. IgG takes a little longer to go up and then it stays there.So, we say IgG is solid.”

Another diagnostic, notes Chatfield, would be a PCR test, for which there are 2. “The legacy PCR,” explains Chatfield, “tells you that you have some genetic material consistent with lepto present. We don’t know if the pathogen is actually viable.” But the quantitative PCR (qPCR), she notes, can be more exacting. “The qPCR test measures the amount, so if it comes back at a high level, then you know the dog has lepto,” says Chatfield.

Lesson learned: A qPCR test with a molecular antibiotic resistance panel will give you the most accurate reading of whether a dog has leptospirosis.

For case number 2, an 8-year-old dog presented with bad periodontal disease, vomiting and a deep, productive cough. The dog is up to date on vaccines and mildly dehydrated but was boarded for several days some time prior. Upon examination, a heart murmur was also detected. The dog is treated with fluids and an antibiotic, but symptoms are not fully resolved. A radiograph is done and a QPCR, which comes back negative. Radiograph reveals evidence of aspiration pneumonia, and in fact, the dog has kidney failure. “I would tell the owners of the dog to look behind the couch, because this dog has probably been throwing up for some time.” The veterinarian might not have looked deeper and discovered kidney failure had they relied on the owners reporting of one episode of vomiting.

Lesson learned: “If you start with an already established list of differentials, you are going to miss stuff,” advises Chatfield. “So don’t look under the fence, kick the gate open.”

With her final case, Chatfield presents a 7-year-old dog with lethargy and vomiting, up to date on her vaccinations. Prescribed antibiotics did not work. Blood work and imaging is done, and the QPCR test is positive for leptospirosis.The family had moved to a 3-year schedule for vaccination, and the dog, in fact, had not been up to date on her boosters for leptospirosis.

Lesson learned: “A lot of people think older dogs don’t have to come in for their annual vaccines,” says Chatfield. Think again!

Finally, Chatfield presented her “3 Truths and a Lie” scenarios:

Statement: Leptospirosis is found everywhere, not just in tropical areas:
TRUE. Leptospirosis is presented worldwide, except for Antarctica; increased rainfall can also increase leptospirosis in the environment. Additionally, leptospirosis is often contracted where other dogs congregate.

Statement: Little dogs in urban areas are more likely than big dogs in rural areas to become infected with leptospirosis.
TRUE. Living in an urban area poses a higher risk for leptospirosis.

Statement: Vaccinations for leptospirosis are safe even for dogs as young as 8 weeks old.

TRUE. Vets often don’t vaccinate until 12 weeks old, often because they feel that maternal antibodies are protecting the puppy.“But maternal antibodies fall off anywhere between 8 and 12 weeks,” noted Chatfield, and current guidelines say that it is safe for puppies 8 weeks of age and older to receive a leptospirosis vaccination.

Statement: Significant adverse reactions to leptospirosis are more common than significant reactions to other vaccines.
FALSE In a large study of over 1 million dogs, the data showed that adverse reaction rate was 0.3% for for dogs vaccinated for leptospirosis.

Reference
Chatfield J. Three truths & a lie: canine leptospirosis. Presented at: American Veterinary Medical Association Convention; Austin, TX: June 21-25, 2024.