Equine Leptospirosis: Disease Overview, Risks and Ramifications

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1 Equine Leptospirosis: Disease Overview, Risks and Ramifications Mark V. Crisman DVM, MS, DACVIM Senior Veterinarian- Zoetis Adjunct Professor Virginia-Maryland College of Vet Med LEPTOSPIROSIS ETIOLOGY Leptospirosis bacterial disease caused by spirochetes 3 Gram-negative aerobic bacteria Motile spirochete with hooked end Organism thrives in wet, warm conditions, neutral to slightly alkaline ph 3 Ideal temperature 82-86ºF but can survive as low as 32ºF Inhabits renal tubules in chronic carriers Electron micrograph of Leptospira interrogans. Photo courtesy of Leptospira and Leptospirosis, 2nd ed. 8 1 Presentation Title 00/00/12 (Optional) 2 Presentation Title 00/00/12 (Optional) LEPTOSPIRA PATHOGENESIS 22 species of Leptospira; pathogenic, intermediately pathogenic and nonpathogenic More than 250 pathogenic serovars of Leptospira based on surface LPS currently recognized 4 At least 12 pathogenic species and four nonpathogenic species 4 Six serovars considered most clinically significant in horses 4 L. interrogans serovar Pomona L. interrogans serovar Grippotyphosa L. interrogans serovar Icterohaemorrhagiae L. interrogans serovar Canicola L. interrogans serovar Bratislava L. borgpetersenii serovar Hardjo MAINTENANCE VS. INCIDENTAL HOSTS Maintenance (reservoir) host 5-8 Hosts maintain organism and are vital to dissemination Hosts become infected young and harbor in kidneys Low pathogenicity to host Disease mild and subclinical Prolonged excretion in urine Incidental (accidental) hosts 5-8 More severe clinical disease and clinical signs Strong immune responses Short period of bacterial shedding For most serovars, horses are incidental hosts 5-8 Leptospira interrogans serovar Bratislava can exist in horses without causing disease, and horses may be maintenance hosts Can maintain high titer even without causing disease 3 Presentation Title 00/00/12 (Optional) 4 Presentation Title 00/00/12 (Optional) SOURCES OF LEPTOSPIRES Each serovar is maintained in reservoir hosts L. pomona cattle, swine, wildlife (striped skunk, raccoon, white-tailed deer, opossum) 9 L. grippotyphosa vole, raccoon, skunk, opossum L. icterohaemorrhagiae rodents (rats) L. canicola dog L. bratislava rat, swine, +/- horse L. hardjo cattle, farmed red deer, +/- sheep and goats SOURCES OF LEPTOSPIRES Leptospires are maintained in the renal tubules of reservoir hosts 6,7 Excreted into the environment in urine Bacteria contaminate natural water sources 6,7 Streams, lakes, stagnant water, mud Under ideal conditions (warm and wet) leptospires can survive in the environment for up to several months 5,10 Higher incidence of disease noted in heavy rainfall or flooding 5,10 Highland cattle in standing water. Photo courtesy of Dr. Amy Poulin. 5 Presentation Title 00/00/12 (Optional) 6 Presentation Title 00/00/12 (Optional) 1

2 DEVELOPMENT OF LEPTOSPIROSIS -following contact with contaminated environmental reservoirs.. Systemic spread to lymphatics and bloodstream, results in bacteremia 4-10 days post-infection Colonization eyes, genital tract, kidney, liver, meninges Concentration and portal of exit 7-10 days after infection leptospires concentrate in the renal tubules and are excreted in the urine 7 Presentation Title 00/00/12 (Optional) From Divers, T: Leptospirosis, p In Sprayberry (ed): Robinson s Current Therapy in Equine Medicine, 7 th ed., Elsevier, St. Louis, MO, DISTRIBUTION OF LEPTOSPIRES Worldwide distribution causing disease in multiple species 1 Domestic animals, wildlife and humans Cattle, pigs, buffalo, dogs and horses Leptospirosis is a zoonotic bacterial disease that can cause symptoms in humans 1 Leptospires are transmitted between species through urine and uterine discharges shed into the environment 8 Presentation Title 00/00/12 (Optional) ZOETIS EQUINE LEPTOSPIROSIS SEROPREVALANCE STUDY 2 Zoetis Equine Leptospirosis Seroprevalence Study 2 5,261 healthy horses sampled Clinics: 53 clinics 18 states <10 horses from any one horse facility Horse history form completed: Age, sex, breed, primary use, prior exposure to leptospirosis Horses enrolled cannot have been vaccinated with an off-label leptospiral vaccine in the past two years Titers 1:100 (MAT) = positive for exposure If multiple serovars were positive, serovar with the highest MAT titer was considered the exposure titer and other results were not counted If multiple serovars had equivocal titers, all were counted 9 Presentation Title 00/00/12 (Optional) 10 Presentation Title 00/00/12 (Optional) REGIONAL REPRESENTATION State percentages from the Zoetis Leptospirosis Serologic Study 2 were calculated to depict regional seroprevalence Percentages represent horses positive for at least one leptospiral serovar at MAT 1: Presentation Title 00/00/12 (Optional) 12 Presentation Title 00/00/12 (Optional) 2

3 PERVASIVENESS OF LEPTOSPIRAL ORGANISMS Strong evidence of broad-based exposure of healthy horses to a variety of leptospiral serovars in the U.S. and Canada 2,12 75% seroprevalence across the U.S. (1:100 MAT cutoff) 2 45% seroprevalence in U.S. and Canada (1:200 MAT cutoff) 12 L. POMONA MOST FREQUENTLY IDENTIFIED SEROVAR IN HIGH-TITER (>1:3200) INDIVIDUALS 2 Seroepidemiology of equine leptospirosis using diagnostic laboratory specimens from 29 U.S. states and one Canadian province 1,495 total horses 12 Serovar Seropositive at >1:100* Percent of Total Horses Number of Horses with Titers 1:3200* Pomona % 9 Bratislava % 6 Grippotyphosa % 7 Hardjo % 1 Canicola % 2 Icterohaemorrhagiae % 1 13 Presentation Title 00/00/12 (Optional) TOTAL *Horses presumed healthy 14 Presentation Title 00/00/12 (Optional) 1,015 positive horses out of 1,495 total EQUINE LEPTOSPIROSIS SEROPREVALENCE SUMMARY 2 Approximately 75% exposure across the country 2 Farm-level exposure had highest level of correlation with exposure to Leptospira and to a specific serovar Region, age, breed, sex, primary use, vaccination and exposure status are all associated with variation in Leptospira titers but accounted for <5% of variabilty 2 ROLE OF CROSS-REACTIVITY IN LEPTOSPIRAL INFECTIONS Horses can react serologically to many serovars prevalent in the environment, but natural infections are from only a few serovars. 27 Acute leptospiral infections can cause marked increases in serum antibody titers to multiple serovars, but the noninfecting serovar(s) decline(s) faster over several weeks than the actual infection serovar. 6 Leptospira interrogans serovar Pomona is the prominent incidental serovar associated with known disease in horses Presentation Title 00/00/12 (Optional) 16 Presentation Title 00/00/12 (Optional) Equine Leptospirosis Clinical Presentations CLINICAL ENTITIES Equine clinical findings 6 Abortion/prematurity Equine recurrent uveitis (ERU) Renal disease Leptospiral-associated uveitis Photo courtesy of Dr. Brian Gilger. Aborted fetus due to leptospirosis Photo courtesy of Dr. Carney Jackson. Pyogranulomatous nephritis due to leptospirosis Photo courtesy of Dr. Carney Jackson. 17 Presentation Title 00/00/12 (Optional) 18 Presentation Title 00/00/12 (Optional) 3

4 LEPTOSPIRAL ABORTIONS IN MARES May be endemic on some farms and in certain regions 6,12 Most abortions are late-term (>9 months) 6 Rarely live foal born 6 Aborted mares can shed leptospires in urine into the environment for up to 2-3 months 6 LEPTOSPIRAL ABORTIONS IN MARES L. pomona is the equine serovar responsible for 86% of leptospiral-associated abortion cases 12 Rarely L. grippotyphosa and L. hardjo also have been identified 6,12 Leptospiral-associated abortions account for 13% of bacterial abortions in mares in endemic areas 6 2.2% to 4.4% of all abortion submissions to the University of Kentucky Veterinary Diagnostic Laboratory were caused by Leptospira Presentation Title 00/00/12 (Optional) 20 Presentation Title 00/00/12 (Optional) 86% OF CONFIRMED LEPTOSPIRAL FETAL ABORTIONS WERE ASSOCIATED WITH L. POMONA ACROSS 9-YEAR TIME FRAME 12 DIAGNOSIS OF LEPTOSPIRAL ABORTIONS OR EARLY FETAL DEATH Titer Pomona Ictero SEROVAR Canicola Grippo Hardjo 1: : : : : : : : : : TOTAL Data courtesy of Dr. Craig Carter. Fetal liver hepatocellular dissociation/ degeneration Fetal liver swelling, friable, yellow discoloration Interstitial nephritis from aborted fetus Fetal kidney swelling with white radiating streaks indicating nonsuppurative to granulomatous interstitial nephritis All photos courtesy of Dr. Carney Jackson and Dr. D Newman, University of Kentucky Veterinary Diagnostic Laboratory. 21 Presentation Title 00/00/12 (Optional) 22 Presentation Title 00/00/12 (Optional) EQUINE RECURRENT UVEITIS EQUINE RECURRENT UVEITIS ERU Periodic ophthalmia Moon blindness Most common cause of blindness in horses! 13 Hallmark is recurrence or persistence of anterior uveitis History Mostly identified initially in 2- to 8-year-olds Two or more episodes within 2 years Quiet eye between episodes 23 Presentation Title 00/00/12 (Optional) Photos courtesy of Dr. Brian Gilger. Pathogenesis Immune-mediated disease Many bacterial, parasitic and viral triggers hypothesized Leptospira interrogans is the #1 inciting cause of ERU 13 70% of ERU is leptospiralassociated 14 Organisms identified in the eye of some but not all affected horses Elevated antibody titers in aqueous humor 15,16 24 Presentation Title 00/00/12 (Optional) Synechia Photo courtesy of Dr. Jaci Boggs. Peripapillary depigmentation Photo courtesy Dr. Brian Gilger. 4

5 ERU-PRESENTING COMPLAINTS ERU OUTCOMES Painful eye(s) Conjunctivitis Corneal cloudiness Early on, the symptoms may be mild and confused with conjunctivitis or environmental irritation With progression Anterior chamber aqueous flare, hyphema, hypopyon, fibrin Miosis Horse with blepharospasm secondary to uveitis. Photo courtesy of Dr. Ann Dwyer. Equine eye with signs of uveitis. Photo courtesy of Dr. Brian Gilger. Corneal scarring Recurrent painful eye Peripapillary depigmentation Corneal edema Synechia Cataract formation Chorioretinal scarring Retinal detachment BLINDNESS! Significant economic 15,17,18 and emotional impact on horses and owners Cataract ERU All photos courtesy of Dr. Brian Gilger. Cataract, posterior synechia Retinal detachment 25 Presentation Title 00/00/12 (Optional) 26 Presentation Title 00/00/12 (Optional) ERU AND BREEDS LEPTOSPIRA AND RENAL FAILURE 3,19 Certain breeds have higher incidence of disease 13 Appaloosa European warmblood Drafts Supports a genetic factor MHC class I haplotype ELA-A9 Appaloosas are 8x more likely to be affected by ERU 13 Bilateral in 80% of Appaloosa cases 13 Photo courtesy of Kim Uthe. Fever Azotemia Low urine specific gravity Pyuria w/o bacteria seen Renomegaly Tubulointerstitial nephritis Positive silver staining Leptospires bacteria Kidney: nonsuppurative interstitial nephritis However, all horses of any breed are at risk of developing clinical disease Appaloosa with ERU Photo courtesy of Dr. Brian Gilger. Leptospiral-induced pyogranulomatous nephritis All photos courtesy of Dr. Carney Jackson and Dr. D. Newman. 27 Presentation Title 00/00/12 (Optional) 28 Presentation Title 00/00/12 (Optional) LEPTOSPIROSIS TESTING Microscopic Agglutination Titer (MAT) Antibody titers measured Most frequently used method 21 On serum, urine or aqueous humor (AH) Panel of serovars Other tests 21 Culture Concentrates in urine Long incubation time and can have low sensitivity without enrichment Direct dark field microscopic exam Fluorescent antibody testing (FAT) Histologic staining (Warthin-Starry stain) Polymerase chain reaction (PCR) Leptospires in urine with Warthin-Starry silver stain Photo courtesy of Dr. Carney Jackson. MICROSCOPIC AGGLUTINATION TEST (MAT) TITERS Antibodies present 4-7 days after exposure Laboratories perform 5 or 6 serovar panel Cross-reaction between the serovars occurs Unequivocal diagnosis with four-fold rise baseline MAT titer to convalescent titer 21 Single MAT titer does not differentiate between exposed/infected Significant MAT titer elevations seen in acute renal failure and abortion cases (into thousands) If positive for multiple serovars, infecting serovar remains high longer Presentation Title 00/00/12 (Optional) 30 Presentation Title 00/00/12 (Optional) 5

6 MICROSCOPIC AGGLUTINATION TEST (MAT) TITERS For suspected leptosprial-associated ERU, MAT on both aqueous humor and serum is most diagnostic +/- PCR 15,16 Leptospira interrogans serovar Pomona is the serovar most frequently associated with clinical disease 6 Aqueocentisis Photo courtesy of Dr. Brian Gilger. ECONOMIC IMPACT OF LEPTOSPIROSIS LEPTOSPIROSIS CAN BE A COSTLY DISEASE Leptospires colonize the kidney and are shed in the urine. Horses can become septicemic which can lead to abortion, uveitis or acute renal failure. $2.1 BILLION The estimated economic impact of leptospiral-associated ERU in the U.S., including the cost of diagnosis, treatment and loss in horse value due to visual impairment or blindness. 14,16,22-25 $102 MILLION The estimated losses from leptospiral-associated abortions in Thoroughbred horses in Kentucky from x INCREASED RISK Risk of abortion increases in wet years as compared with normal rainfall years. 7,10 31 Presentation Title 00/00/12 (Optional) 32 Presentation Title 00/00/12 (Optional) SUMMARY Leptospirosis in horses is likely an underdiagnosed disease. Leptospirosis is capable of causing substantial economic and emotional impact to horse owners and the equine industry. Two of the most economically important diseases caused by pathogenic Leptospira spp. are equine recurrent uveitis (ERU) and abortion. 400,000 horses in U.S. are likely affected with ERU. Loses due to abortion can mount to $1.3 million in Thoroughbred industry alone, representing the tip of the iceberg. In seasons of heavy rainfall, the risk of leptospiral-associated abortions rises 3.7 times. Prevention relies on biosecurity, minimizing exposure to risk factors and client education. *Currently there are no vaccines with USDA licensed label claims agains abortions, recurrent uveitis or acute renal failure caused by L. pomona. 33 Presentation Title 00/00/12 (Optional) Introducing 34 Presentation Title 00/00/12 (Optional) EQUINE LEPTOSPIRA POMONA BACTERIN Species: Equine Route of Administration: Intramuscular Volume: 1 ml Contents: Equine L. pomona bacterin contains inactivated whole-cell cultures of L. pomona with MetaStim adjuvant to help enhance the immune response. Indications: This product is recommended for the vaccination of healthy horses, 6 months of age or older, as an aid in prevention of leptospirosis caused by Leptospira interrogans serovar Pomona. Primary vaccination: Healthy horses should receive an initial two doses three weeks apart. Revaccination: Annual revaccination with a single dose is recommended. 35 Presentation Title 00/00/12 (Optional) DEMONSTRATED TO BE SAFE AND EFFECTIVE In safety and efficacy trials, was shown to help provide a safe immune response 33,34 Field-safety testing has demonstrated that LEPTO EQ INNOVATOR is safe for use in healthy horses and in foals 3 months of age or older 34 Field-safety testing demonstrated LEPTO EQ INNOVATOR can be safely used in healthy pregnant mares in the second trimester Presentation Title 00/00/12 (Optional) Photo courtesy of Dr. Nichole Logan. 6

7 EFFICACY DATA female horses, 6 months of age at first vaccination 15 vaccinates, 15 controls MAT negative to: L. pomona, L. bratislava, L. canicola, L. grippotyphosa, L. hardjo, L. icterohaemorrhagiae Challenged with Leptospira interrogans serovar Pomona on three consecutive days (IP) 0% URINARY SHEDDING Horses vaccinated with and challenged with L. pomona showed 0% urinary shedding, which can help reduce the spread of disease. Controls (n=15) Vaccinates (n=15) Fever ( 103.0) 10 3 Blood Isolation 15 0 Urine Isolation 14 0 Kidney Isolation 3 0 Total Positive Isolation 100% 0% 37 Presentation Title 00/00/12 (Optional) 38 Presentation Title 00/00/12 (Optional) EFFICACY DATA SUMMARY 33 Immunogenicity demonstrated by vaccination and challenge test in 6-month-old healthy horses. Horses were vaccinated with two doses of LEPTO EQ INNOVATOR and subjected to experimental challenge at three weeks post-vaccination. 100% of control animals were positive for leptospiremia, while no vaccinates were positive for leptospiremia. 93% of the controls tested positive for leptospiuria, while no vaccinates were positive for leptospiuria. Duration of immunity has not been established DEMONSTRATED SAFE IN SECOND TRIMESTER BROODMARES 35 was field tested in pregnant mares 338 (225 vaccinates, 113 controls) broodmares across the U.S. were enrolled. No immediate systemic or local reactions observed in any broodmare following administration of 2-dose vaccine series. Mares represented first trimester (n=13), second trimester (n=298) and third trimester (n=27), including saline controls. No unexpected adverse events related to vaccine administration. Abortions: no fetuses recovered from two mares found open on final study day, diagnostics performed on mares with no cause identified; 0.695% incidence of mares vaccinated in second trimester, which is well below the estimated 6-10% natural rate of abortion in mares greater than 40 days of gestation. 31,32 39 Presentation Title 00/00/12 (Optional) 40 Presentation Title 00/00/12 (Optional) 99.8% REACTION-FREE demonstrated to have a low reaction rate In 1,019 horses across multiple geographic areas following administration of 1,808 vaccine doses only 3 local reactions observed that resolved without incidence 34,35 Phase 1: Total 681 horses included Foals 3 months (n=207) 34 Horses 4 months of age (n=474) 34 Phase 2: Broodmares (n=338) 35 # Horses # Injections # Site Reactions Phase Types of Horses Foals < 3 months (207) Horses > 4 months (474) Phase * 0 Pregnant Mares 2-21 years Total 1,019 1,808* 3 *Saline control horses removed for calculation Will the vaccine initiate uveitis in genetically predisposed horses? 9 Adult Apps, 3-17 yrs, MAT titers < 16, no clinical evidence of uveitis Horses vaccinated IM 7x over a 5 month period Horses observed for 1 yr. At conclusion- MAT of AH samples plus total ocular histologic exam CONCLUSION; Vaccine did not result in any cases of uveitis or uveitic flares as detected by gross examination. At microscopic level -WNL 41 Presentation Title 00/00/12 (Optional) 42 Presentation Title 00/00/12 (Optional) Appaloosa with ERU 7

8 Effect of vaccination against leptospirosis on the frequency, days to recurrence and progression of disease in horses with equine recurrent uveitis Vet. Ophthalmology (2005) Barton W. Rohrbach,* Daniel A. Ward, Diane V. H. Hendrix, Margaret Cawrse-Foss 41 horses with ERU (control & treatment groups) Vaccinated with 6 serovar vaccine (swine) recurrence of uveitis verified by ophth. exam and compared with progression of disease Results; after 2 nd vaccination, days to first recurrance significantly longer (mean126 days) compared with controls (86 days) CONCLUSION; Vaccine significantly > days to recurrence but failed to slow progression of disease. These data do not support the use of vaccination against lepto as adjunct therapy for tx of horses with ERU 43 Presentation Title 00/00/12 (Optional) KEY TAKEAWAYS Leptospira interrogans serovar Pomona (L. pomona) can cause devastating disease in horses. It can colonize in the kidney, shed in the urine and horses can become septicemic along with causing abortion, uveitis and acute renal failure. is the first vaccine developed specifically for horses to help prevent leptospirosis caused by L. pomona. Efficacy studies have demonstrated LEPTO EQ INNOVATOR helps prevent urinary shedding and septicemia. LEPTO EQ INNOVATOR is demonstrated safe and 99.8% reaction-free. SPRING Fayette Co KY- 26 confirmed Lepto abortionsnone of the mares were vaccinated for Lepto 44 Presentation Title 00/00/12 (Optional) EQUINE LEPTOSPIRA VACCINE SUMMARY Questions? is recommended for the vaccination of healthy horses, 6 months of age or older, as an aid in prevention of leptospirosis caused by Leptospira interrogans serovar Pomona. Efficacy has been demonstrated to aid in the prevention of leptospiremia and leptospiuria 31 Contains whole-cell monovalent Leptospira interrogans serovar Pomona bacterin Adjuvant with MetaStim Antigen purification process Diafiltration Has not been demonstrated to help prevent uveitis, abortion or acute renal failure caused by L. pomona 45 Presentation Title 00/00/12 (Optional) 46 Presentation Title 00/00/12 (Optional) mark.crisman@zoetis.com 8