A practical review of leptospirosis (Proceedings)

Leptospirosis

•Most common zoonosis worldwide.

•Bacterial disease caused by pathogenic Leptospira species affecting domestic animals, wildlife, and humans.

Leptospira

•smallest spirochete bacteria

(0.1 µm x 6-30 µm)

•tightly coiled

•pointed ends which are bent into distinctive hooks

•gram negative

•Does not stain well!

•motile

•spirochetes - typical double membrane structure

•Cytoplasmic membrane and peptidoglycan cell wall are closely associated and overlain by an outer membrane

•Leptospiral lipopolysaccharide

•composition similar to other gram-negative bacteria, but lower endotoxic activity

•Surface protein/outer membrane proteins (OMPs)

•Lipopolysaccharides (LPS) and lipoproteins

•LPS – highly immunogenic, responsible for

serovar specifity

Cornell and Gluck are looking at these surface proteins to help improve serologic testing

ENVIRONMENT

•Leptospira in rivers, lakes, and sewage.

•Heat (>93 F) and Cold (< 50 F)

•Detrimental to the organism

•Alkaline Soil

•> 8 or < 6 pH not suitable for survival

•Soil contaminated with urine

•~ 2 weeks (RATS or VOLES)

•~ 7 weeks (New Zealand Winter)

PATHOGENESIS

•Increased prevalence during rainy periods in spring and fall.

•TEMPERATURES:

• September 23 – November 3 Average temp was >65 compared to ↓ 65 baseline year(Dr. Hall Thesis 2005)

•Host-adapted - most common reservoirs are raccoon, skunk, deer, cattle, swine, and rats.

•Equine - adapted host – Bratislava

• Never isolated from the horse but high titers (Persistent)

•Exposure occurs when horses consume contaminated groundwater that contains urine shed from a host-adapted species.

•Leptospira are able to penetrate mucous membranes and abraded skin.

•Rapidly gain access to vascular space.

•Bacteremia persists for about 8 days.

•FEVERS 103-106 F 7-9 days after exposure (US Livestock Sanitary Assoc- Morter et al, 1964, JAVMA 1969)

•Invasion of many internal organs occurs.

•No Tropism

•The infection induces a strong host antibody response – 1st detectable in serum 4-8 days after exposure. (US Livestock Sanitary Assoc- Morter et al, 1964, JAVMA 1969)

•Maintain for up to 7 years (Swart Aus Vet J 1982)

•Organisms are eliminated rapidly from the blood and most organs by host mechanisms – TH2-response.

•Interferon Gamma

•Localization of organisms may occur in :

•Genital tract

• Renal tubules

•Anterior and posterior chambers of the eyes.

•Infected horses may shed pathogenic leptospires in the urine for up to 4-5 months. (Morter et al, 1964, Bernard 1993)

Clinical Signs

•VAGUE!

•Fevers

• Weight Loss/Anorexia

•Intermittent Colic

•Azotemia (Renal)

•Hematuria/Pigmenturia

•Anemia

•Abortion

•Uveitis

CLINICAL MANIFESTATIONS

•UVEITIS

•RENAL DISEASE

•ABORTION

UVEITIS

•Most frequently encountered clinical manifestation of leptospirosis in horses.

•Unilateral OR Bilateral

•Recurrent AND Progressive

•Early - epiphora, photophobia, blepharospasm, miosis, corneal edema, conjunctivitis, keratitis

•Susequent exacerbations -hypopyon, hyphema, fibrin in anterior chamber, synechiae, cataract

•Blindness (Severe Cases)

•When?

•6 weeks-24 months after infection

•How?

•Antibodies against Leptospira were detected in tears , aqueous and vitreous humor

•Bind to equine cornea and produce corneal opacity.

•The immune response of ERU is directly induced and maintained by persistent leptospiral infection of the eye (intraocular antibody synthesis).

•High Prevalence of PCR Lepto + in Uveitis cases VS Controls

•Treatment

•Goals:

•relieve pain

•preserve vision

•reduce and control ocular inflammation

•Medication:

•Mydriatic-cycloplegics

•Corticosteroids: Topical/Systemic or Subconjunctival (2mg Vetalog)

•NSAIDs (topical and systemic)

•Cyclosporine ?

•Vitrectomy (98% no further attacks of ERU)

•GERMANY: But Increased incidence of CATARACT!

•Intracameral Injection

•1cc Gentocin

•SYSTEMIC TREATMENT

•Tough because of blood ocular barrier

•LA-200 (6.6 mg/kg IV SID or BID)

•Doxycycline 10mg/kg PO SID

•Efficacy? 5mg/kg PO BID to Ponies

•NO LEVELS DETECTED IN AQEOUS HUMOR

•Baytril 7.5 mg/kg PO SID for 2 weeks?

•Divers et.al. Unpublished data

ACUTE RENAL FAILURE

•Initially Vague Signs

•Intermittent Fevers

•Off Feed

•Not Thriving

•Initial Blood Work

•Normal

•2-3 weeks later = Elevated Kidney Enzymes

•Reported in 1 stallion, 1 mare, weanlings and foals

•4 ARF in TB-yearlings in Lexington, KY in June 2006 (HEMI-not published)

•2 weeks previously: Sales Prep Movement

•High Fevers in these 4 animals 105 +/-

•Treatment

•IVF

•Diuresis (Aminophylline, Mannitol and/or Lasix)

•Antibiotics –

•Penicillin (30-40,000 IU/kg IV QID)

•Baytril

•Ticarcillin-clavulonic acid have been given

•Prognosis

•Good with early and effective treatment

ABORTIONS AND PREMATURE FOALS

•Subclinical most of the time

•Mare might or might not exhibit clinical signs (fever) at time of infection but abortion might occur later in disease process – generally no premonitory clinical signs

•Abortion 3-4 weeks later in Clinical Cases

•Sporadic cause of placentits, abortion, premature births (more common in KY)

•Abortions occur in last third of gestation

• Infected premature or full-term, weak, icteric foal

•Hydrops Allantois

•1 TB mare (HEMI-Unpublished)

Abortion

•PLACENTA (Poonacha 1993 Vet Path)

•80% Gross Lesions

•96% Histopathologic Lesions

•Edematous

•Greenish Discoloration of Allantoic Surface

•Nodular Allantoic Masses

•Calcified Plaques amnion

•Spirochetes

•stroma and villi of placenta

•attach to epithelial cells

•causing vasculitis, thrombosis, endothelial damage, inflammatory cell infiltrates

•Prophylactic Treatment of Mare:

•LA-200(6.6 mg/kg IV SID or BID)

•Doxycycline (10mg/kg PO BID) 7-14 days

•Penicillin

•Baytril?

•Premature Foal

•High Doses of K-Pen (30-40,000 IU/kg IV QID)

•Prognosis: Still Learning

•88% success rate of rebreeding and carrying a live foal after a Lepto abortion. (Dr Hall Thesis 2005)

•1990 Confirmed cases = 27 Live Live Thoroughbred foals in KY= 7397

•Estimated prevalence of Lepto induced abortion per live foals in KY TB = .0037 (37/10,000) born

•2004 Confirmed cases = 24

Live Thoroughbred foals in KY = 13797

•Estimated prevalence of Lepto induced abortion per live foals in KY Tbs = .0017 (17/10,000)

Diagnostics

Antigen Detection

•ELISA

•PCR

•Both Tests in Development for Equine at Gluck

•Tissue and Urine Samples

•John Timoney

Serological Diagnosis

•Most common diagnostic tool.

•Antibodies are detectable in blood approx. 5-7 days after onset of symptoms.

•Genus specific

•Serogroup specific

•Microscopic Agglutination test (MAT)

(reference method for serological dx of leptospirosis)

MAT

•Patient sera are reacted with live antigen suspensions of leptospiral serovars – examined microscopically (dark-field) for agglutination – titers determined.

•Risk of cross-reactions.

•Paired sera are required to confirm a diagnosis.

•Insensitive. (esp. in early acute-phase specimen)

•WHAT TITER LEVEL IS SIGNIFICANT?

•Donahue et al. 1991-1993 JVID

•94.4 % of Abortions had Titers ≥ 12, 800

•5.6 % of Abortions has Titers Between 1,600 and 6400.

•Other Articles: Very Similar Findings

•UVEITIS

•Confusing because of the lag time of clinical disease

•RENAL

•Limited data: Most likely Similar to Abortion

•WHAT TITER LEVEL IS SIGNIFICANT?

•Williams EVJ 1994 : 3 Farms with Hx Lepto

•1178 Samples

•43/1178 (3.6%) 3200-6400

•7/1178 (0.6%) ≥12,800

•HAGYARD 2006

•239 MAT TESTS

•Similar DATA to WILLIAMS

MAT and URINE SHEDDING?

•GOOD QUESTION!

•EVJ WILLIAMS 1994

•Looked at Titers > 800

•Urine Collected 1x weekly for 3 weeks

•NO + on FA, Dark-Field OR Culture (only 18 horses)

•BERNARD JAVMA 1993

•6 horses ≥ 6400

•3 horses + on FA only

•105 days, 52 days and 52 days until 3 consecutive "-"'s

•These horses were treated with Dihydrosptepromycin for 3 d

•Then LA-200 5mg/kg IV SID for 5 days

•CANNOT USE MAT to Determine Urine Shedding

Preventative Measures

•Basic precautions.

•Early identification of infected animals.

•Reduce contact with infected animals.

(particularly urine and other body fluids)

•Keep rodent problems under control.

•Keep water sources clean.

•Draining or fencing off standing water.

•VACCINE?

•No approved vaccines on the market

•People have used the Cattle and Pig Vaccines

•Must have serovar-specific vaccine

•Immunity short lived

•UVEITIS (Vet Opht June 05')

•1/2 dose inactivated swine vaccine (2 doses)

•INCREASED DAYS TO REOCCURRENCE

•DID NOT SLOW PROGRESSION OF DISEASE

THANKS

•Craig Carter DVM: UK VDDL

•Mike Donahue DVM and Staff: UK VDDL

•Jackie Smith MS UK VDDL

•Cornell University

•John Timoney : Gluck