Q and A: Leptospirosis – A Hidden Threat for Your Horse

Horse drinking from pool of stagnant water - possible source of equine leptospirosis.
Horse drinking from pool of stagnant water - possible source of equine leptospirosis. Peter Gudella

Newsdate: Friday, April 5, 2024 – 11:30 am
Location: PARSIPANNY, New Jersey

What is Leptospirosis?

Leptospirosis is a bacterial infection caused by spirochetes belonging to Leptospira spp. The bacteria can affect many mammals, including wildlife, cattle, dogs, horses and even humans.

Horse's eye with chronic signs of uveitis.

Horse's eye with chronic signs of uveitis.

A recent nationwide study showed 75% of healthy horses were exposed to at least one leptospiral serovar.
© 2021 by Dr. Rana Bozorgmanesh New window.

Equine leptospirosis is a costly and underdiagnosed disease that can affect the entire equine industry. A recent nationwide study showed 75% of healthy horses were exposed to at least one leptospiral serovar.

What causes Leptospirosis?

Horses often become infected when exposed to:

  • Contaminated soil, bedding, feed and drinking water1,2
  • Standing or slow-moving water3,4
  • Wildlife such as skunks, white-tailed deer, raccoons and opossums
  • Aborted or stillborn fetuses or vaginal discharges1,4

Infected animals can shed the bacteria in their urine.1,4 The Leptospira bacteria can survive for weeks in warm, moist environments.4,5

What effects does Leptospirosis have on horses?

  • Leptospira bacteria are a leading cause of equine recurrent uveitis (ERU).3 It’s estimated that up to 70% of all uveitis cases are associated with leptospires.5,6 There is no cure for ERU.
  • Leptospires can cause late-term abortion in mares. A study showed that 13% of bacterial abortions are caused by L. pomona, the most common leptospiral serovar associated with clinical disease in horses.3
  • Leptospiral infection can lead to acute renal failure when leptospires colonize in kidneys, causing the horse to become septicemic.*

How can I help prevent Leptospirosis?

LEPTO EQ INNOVATOR® is the first and only equine vaccine to help prevent leptospirosis caused by L. pomona and is USDA-licensed for use in pregnant mares. In intensive safety and efficacy trials, LEPTO EQ INNOVATOR was shown to provide a safe and effective immune response.

  • Vaccinated horses showed 0% urinary shedding when challenged with L. pomona.7
  • Field studies showed 99.9% of vaccinated horses were reaction-free with no significant adverse events.8-10
  • Field safety studies examined LEPTO EQ INNOVATOR when used in the first, second and third trimesters of pregnancy and showed no systemic or local reactions were attributed to vaccination.8,9


*Currently, there are no vaccines available with USDA-licensed label claims against equine abortions, uveitis or acute renal failure due to L. pomona.

1 Spickler AR, Leedom Larson KR. Leptospirosis. http://www.cfsph.iastate.edu/DiseaseInfo/factsheets.php. Published August 2013. Accessed September 1, 2016.

2 Thomas H. Leptospirosis in horses. Equine Chronicle. January/February 2015. http://www.equinechronicle.com/leptospirosis-in-horses. Accessed September 1, 2016.

3 Divers TJ, Chang Y-F. Leptospirosis. In: Robinson NE, Sprayberry KA, eds. Current Therapy in Equine Medicine. Vol 6. 6th ed. St. Louis, Mo: Saunders Elsevier, 2009:145-147.

4 Levett PN. Leptospirosis. Clin Microbiol Rev. 2001;14(2):296-326.

5 Polle F, Storey E, Eades S, et al. Role of intraocular Leptospira infections in the pathogenesis of equine recurrent uveitis in the southern United States. J Equine Vet Sci. 2014;34(11-12):1300-1306.

6 Borstel MV, Oey L, Strutzberg-Minder K, Boeve MH, Ohnesorge B. Direkter und indirekter Nachweis von Leptospiren aus Glasköperproben von Pferden mit ERU. Pferdeheilkunde. 2010;2(März/April):219-225.

7 Data on file, Study Report No. B850R-US-12-011, Zoetis Inc.

8 Data on file, Study Report No. B951R-US-15-092, Zoetis Inc.

9 Data on file, Study Report No. B951R-US-13-046, Zoetis Inc.

10 Data on file, Study Report No. B951R-US-13-043, Zoetis Inc.

All trademarks are the property of Zoetis Services LLC or a related company or a licensor unless otherwise noted.

Press release by Zoetis - Note: Article was first posted oon EquiMed.com in 2017

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