By Michelle Evason, BSc, DVM, DACVIM

When I think about leptospirosis in dogs, I immediately think about one case (and client) who left me feeling helpless and heartsick. I've obviously blurred some details in what comes next to protect anonymity; however, like many of the tales we tell in this profession, this case revolves around a pet and their devoted owner. In this case, eight Havanese dogs that lived the good life with their "Mom" near the Atlantic coast.

On a Friday afternoon (of course), we received a call that this client was headed our way with her three Havanese dogs that had all acutely begun vomiting one day prior. We also learned two of her other eight dogs were currently being treated by the referring veterinarian (rDVM) for milder vomiting (n =five sick dogs).

The three dogs being referred were coming for management of acute kidney injury (AKI) identified on rDVM laboratory testing of blood and urine, IRIS staged as AKI IV(O).¹ One immediate differential proposed was toxin ingestion, and I also argued for consideration of infectious, i.e., leptospirosis. This is where things began to go sideways; I soon discovered a rapid way to test for leptospirosis was not available at the clinic. The next clinical stumbling block became hospital management, infection control, and public health, as once the "L-word" is uttered it cannot be taken back. Unfortunately, appropriate leptospirosis infection control protocols were not yet in place for the ICU.

We did the best we could, as one too often feels one does in this profession, our team received the dogs with infection control in mind (PPE, etc.), performed physical exams, collected samples (blood and urine), placed IV access (jugular and cephalic catheters), calculated fluid rates and urine output, and performed imaging (chest radiographs, abdominal ultrasound).

We began ampicillin IV (due to oral medication intolerance), supportive care (anti-emetics, analgesia, nutritional support), and also placed "lepto suspect" signs on the dog's ICU cages to ensure appropriate precautions were taken when handling the dogs and environment (e.g., bedding).

We also had a frank (sad and difficult) conversation with the dogs' devastated, exhausted, and worried owner, regarding prognosis, the lack of dialysis as an option, and need for constant ongoing adjustment of prognosis based on serial AKI staging.¹

As most veterinary personnel can relate to, as we all have our stories of cases like this, all of us on the hospital ICU team fought to stabilize and care for these dogs for the next week. Sadly, two dogs were euthanized due to their deteriorating condition, and one recovered with ongoing chronic kidney disease (CKD). The dogs that were sick, but not referred, were started on fluids and doxycycline by the rDVM (in consultation with us) and recovered.

There were several very hard conversations about why vaccination for leptospirosis (eventually confirmed in all five sick dogs) was reportedly never offered to this client. A few more difficult conversations occurred with a couple of human health care providers, as medical history-taking revealed this pet owner was receiving immunosuppressive treatment post-transplant.

I think about these dogs and their owner every time I think about leptospirosis. While it does not change what happened or make the sick feeling of failure as a clinician completely go away), I hope (like I know some of us out there do) every time I write, speak, or publish about this infectious disease it helps: 1) promote vaccination in more dogs, which then prevents them from ever becoming ill with lepto, 2) allow quicker diagnosis (due to vet awareness, getting it on differential lists, current availability of rapid diagnostic tests, and hospital stocking of these), and 3) minimizes risk of human illness by getting clinicians and practices to plan ahead through the implementation of appropriate infection control protocols, and prompt initiation of appropriate antimicrobials, along with awareness of human risk. 

Leptospirosis and serovars

In recent years, there seems to have been a global jump in dogs diagnosed with leptospirosis, ^2-7 with specific U.S. and Canadian "lepto hot spots" identified based on commercial laboratory canine results.^2,3 These "hot spots" are regions where dogs appear likely to be exposed to, and subsequently infected with, the gram-negative bacteria Leptospira interrogans sensu lato, the agent of leptospirosis.

Regrettably, whether one considers leptospirosis "emerging," "endemic," or a combination of the two, this pathogen is an ongoing global One Health concern.^2-7

Different serovars of Leptospira spp. may be present in a given locale and vary further dependent on wildlife (or not so 'wild') reservoirs that shed the bacteria in their urine, e.g., raccoons, rodents, and kitties (Table).^6-9 In cats, and dependent on study and region, urine shedding (leptospiruria) can be very common.⁹

Importantly, leptospirosis in dogs is almost entirely "vaccine preventable." As such, client communication to inform risk associated with leptospirosis and prevention strategies are critical. Education on leptospirosis prevention should be tailored based on regional and lifestyle exposure risk, i.e., where the dog lives (region), travel plans that take the dog to other regions, lifestyle (e.g., hunting dog), and season of year. The latter (season) is particularly important for those in cooler climates, most notably the Northeast and Midwest U.S. and much of Canada, as lepto risk appears to vary widely based on time of year in these regions, vs. more temperate regions (e.g., southern U.S., Hawaii) where risk is stable year-round.^2,3 Additionally, education on (and awareness of) public health (human) risk surrounding leptospirosis for veterinary teams, clients, and environment, i.e., One Health is key.^6-9 (see Table 1)

Leptospirosis and 'hot spots'

These maps outline current reported leptospirosis and "lepto hot spots" for dogs in the U.S. and Canada (Figures 1 and 2).^2,3 The figures are based on canine test- positive PCR results collected over time for both countries.

Leptospirosis risk factors in dogs and cats

Risk factors for leptospirosis in dogs include wildlife and livestock exposure, proximity to urban centers, outdoor activities, water exposure (puddles—especially for small breed dogs, post-flooding, rainfall), and lack of vaccination.^2-7

In cats, leptospirosis risk factors include outdoor lifestyle, urban environment, and multi-cat households.⁹

Clinical presentation of leptospirosis

The common outcomes of leptospirosis in dogs can be clinical disease that ranges from subtle (i.e. "a bit off") to severe renal and/or hepatic compromise.^6-8 Other reported multi-system disease presentations have included generalized muscle tenderness and pain, respiratory or neurologic signs, and bleeding tendencies, e.g., epistaxis, petechiation, etc.^6-8

Leptospirosis in dogs should be considered when there is acute onset of disease, the patient has vague clinical signs (reduced appetite, acting "off," vomiting), or the dog has likely exposure to (lives, visited) a known or emerging risk area.^6-8 Other lepto diagnostic "ding ding dings" include a complete blood count that shows reduced platelets, a serum biochemistry that shows renal or hepatic changes (or both), and dilute urine (+/- proteinuria, +/- glucosuria).^6-8

Various diagnostic algorithms for leptospirosis utilizing the above and specific testing (lepto antibody-serology (IgM, IgG), PCR, MAT) have been published,⁸ including a recent machine-learning version.¹¹

There is a paucity of information in cats; however, cats tend to have no or mild clinical signs.^8,9 The few reports of cats presenting with acute disease have included neurologic or GI signs, uveitis, urinary, or generalized muscle tenderness, along with other reports of cats with more chronic CKD or gastrointestinal signs.⁹ A diagnostic algorithm has been published for cats.⁹ 

General recommendations for prevention

Dogs: Vaccination is available against the four common pathogenic lepto serovars (Canicola, Pomona, Icterohaemorrhagiae, Grippotyphosa). Ideally, vaccination is administered at the first puppy exam (eight weeks or older, and repeated two to four weeks later), and then annually to ensure vaccination coverage as per the American Animal Hospital Association (AAHA) vaccination guidelines.¹⁰

Although lepto is considered a noncore vaccine, for those in known risk regions (or for dogs travelling to risk regions), vaccination is strongly advised.

Adverse events after leptospirosis vaccine have been determined to be very low overall, with 53/10,000 (0.5 percent) dogs receiving a leptospirosis vaccine having an adverse event as compared to 22/10,000 (0.2 percent) dogs receiving a non-leptospirosis vaccine.¹²

Other aspects of prevention for dogs include reduction of leptospirosis exposure as practical, e.g., monitor for lepto outbreaks, avoid known risk environments, rodent control, etc.

Cats: Reduction of environmental risk (as above) as practical. Currently, there is not an approved vaccine for cats.

Regular client reminders regarding vaccine prevention, pointing pet-owners toward leptospirosis resources and maps, such as those included in this article, and emphasizing the "an ounce of prevention is worth a pound of cure" message can assist with compliance. Communicating results of adverse event studies can assist with "vaccine hesitancy" client concerns.¹²

Public health, zoonosis concerns around leptospirosis

People (pet owners and veterinary personnel) have acquired leptospirosis from pets, and, while this appears to be overall uncommon, precautions are needed. These steps should include lepto risk awareness (signs on cages in clinics if known or suspected case), avoidance of urine contact and limiting where the patient urinates (e.g., designated area), along with appropriate disinfectant (routine), and drying.

Dogs are thought to have stopped shedding leptospires in their urine at 48 to 72 hours post-appropriate antimicrobials, which likely minimizes risk of transmission. However, a recent study has shown persistence of shedding, despite antimicrobials in some dogs, and advised ongoing monitoring due to this concern.¹³

Client counselling on zoonotic concern and common environmental exposure is indicated, along with assessment of risk and potential therapy of other household dogs.^6-8

End note: While I know I cannot bring those Havanese dogs back to health and to the sweet life they had with their devoted owner, I appreciate the opportunity to write about leptospirosis in their memory in hopes it helps raise awareness regarding this largely preventable infectious disease.

Michelle Evason, BSc, DVM, DACVIM (SAIM), has worked in general practice, academia, specialty clinical practice, and in the animal health industry. She serves as global director of Veterinary Clinical Education for Antech and has published on numerous infectious diseases, antimicrobial stewardship, nutrition, and pet-owner education-related topics. Michelle enjoys ferrying her children to various activities and fulfilling most "Canuck" stereotypes.

References

1. Cowgill L, et al. IRIS. Grading of acute kidney injury (AKI). 2016. Accessed July 2022. http://www.iris-kidney.com/pdf/4_ldc-revised-grading-of-acute-kidney-injury.pdf
2. Smith AM, Goncalves AA, Evason M, et al. A cross-sectional study of environmental, dog, and human-related risk factors for positive canine leptospirosis PCR test results in the United States, 2009 to 2016. BMC Vet Res. 2019;15(1):412. https://doi.org/10.1186/s12917-019-2148-6.
3. Stull JW, Evason M, Weese JS, et al. Canine leptospirosis in Canada, test-positive proportion and risk factors (2009 to 2018): A cross-sectional study. PLOS ONE. 2022;17(6): e0270313. https://doi.org/10.1371/journal.pone.0270313
4. Major A, Schweighauser A, Francey T. Increasing Incidence of Canine Leptospirosis in Switzerland. Int J Env Res. 2014; 11(7):7242-7260.
5. Raj J, Campbell R, Tappin S. Clinical findings in dogs diagnosed with leptospirosis in England. Vet Rec. 2021;189(7):e452.
6. Schuller S, Francey T, Hartmann K, et al. European consensus statement on leptospirosis in dogs and cats. JSAP. March 2015;56 (3):159-179.
7. Sykes JE, Hartmann K, Lunn KF, et al. 2010 ACVIM small animal consensus statement on leptospirosis: diagnosis, epidemiology, treatment, and prevention. JVIM. 2011; 25(1), 1-13.
8. Weese JS, Evason M. Infectious Diseases of the Dog and Cat. CRC Press. July 2019.
9. Murillo A, Goris M, Ahmed A, et al. Leptospirosis in cats: Current literature review to guide diagnosis and management. J Fel Med. 2020;22(3):216-228.
10. Ford RB, Larson LJ, McClure KD, et al. 2017 AAHA Canine Vaccination Guidelines. Accessed June 2022: https://www.aaha.org/globalassets/02-guidelines/canine-vaccination/vaccination_recommendation_for_general_practice_table.pdf
11. Reagan KL, Deng S, Sheng J, et al. Use of machine-learning algorithms to aid in the early detection of leptospirosis in dogs. J Vet Diag Invest. 2022; May:1-10. 
12. Yao PJ, Stephenson N, Foley JE, et al. Incidence rates and risk factors for owner-reported adverse events following vaccination of dogs that did or did not receive a Leptospira vaccine. J Am Vet Med Assoc. 2015; 247 (10): 1139-1145.
13. Hetrick K, Harkin KR, Peddireddi L, et al. Evaluation by polymerase chain reaction assay of persistent shedding by pathogenic leptospires in the urine of dogs with leptospirosis. JVIM. 2022; 36:133-140.