Leptospirosis: The return of the Jedi (Proceedings)

• Agent

o Spirochete with more than 200 "serovars." The pathogenic serovars do not replicate outside animal hosts

• Leptospira interrogans

• Serovars: autumnalis, bratislava, canicola, icterohaemorrhagiae, pomona

• Leptospira kirshneri

• Serovar: gryppotyphosa

• Leptospira borgpetersenii

• Serovar: hardjo

o Specific serovars are "hosted-adapted" to certain reservoir species and generally do not cause disease in those hosts, e.g.:

• L. interrogans bratislava pigs, rats, small mammals

• L. interrogans canicola dogs

• L. interrogans icterohaemorrhagiae rats

• L. kirschneri grippotyphosa voles, raccoons, small mammals

• Epidemiology

o Animals are critical to the maintenance of pathogenic leptospires in a given area.

o Leptospires can persist in the renal tubules without causing disease, and can be excreted in the urine for prolonged periods of time.

• Leptospires evade immune responses while sequestered in renal tubules.

o Prevalence in dogs is increasing since 1983

• Risk factors

• Adult (4 – 7 years) intact male dogs

• Herding, working dogs, and hounds

o Enzootic worldwide

• Tropical and semitropical areas

• Alkaline soil

• Leptospires can survive in moist environments for months, but are killed by freezing

o Seasonality

• Summer or fall

• Rainy periods

• Transmission

o Leptospires are eliminated by urine and enter the body through abraded skin and intact mucous membranes

o In dogs, leptospira concentrates in the liver and kidneys

• Clinical signs – 7 days post-exposure

• May clear the infection in 2 – 3 weeks

• May develop chronic renal failure or chronic active hepatitis

o In cats, infections are usually subclinical

• Cats can shed leptospira in the environment

• Clinical Signs

o Many, if not most, Leptospira infections in dogs are subclinical

o L. interrogans icterohaemorrhagiae: Hepatic disease and hemorrhage occur mostly with (may also have sub-acute uremia)

o L. interrogans bratislava: Renal disease predominates with (liver changes also can be present)

o L. interrogans pomona: Renal and liver disease mostly

o L. kirschneri grippotyphosa: Renal and liver disease mostly

o L. interrogans canicola: Mostly renal changes

o Experimental infection

• L. interrogans pomona and L. interrogans bratislava causes hemorrhagic and inflammatory lesions in lungs kidneys and liver.

o Signs

• Fever

• Uveitis

• Vomiting, diarrhea

• Renal failure

• Liver failure

• Jaundice

• Muscle pain

• Laboratory Abnormalities

o CBC

• Leukopenia (acute)

• Leukocytosis (subacute)

• Thrombocytopenia

o Renal failure

• Increased BUN and creatinine

• Cillindruria

• Pyuria

• Hematuria

o Liver disease

• Increased activity of ALT and Alkaline phosphatase

• ALP is usually higher than ALT

• Increased bilirubin

o Interstitial lung disease

• Diagnosis

o Clinical Signs + Serology

• Detection of antibodies

• Antibodies from active infection, previous infection or vaccination

• Active infection

o MAT titer > 3200

o 4 fold increase in titer over 2 – 4 weeks

o Positive IgM ELISA

o Titers can be negative in acute infection

o Vaccine may induce antibodies against L. interrogans automnalis

• Demonstration of the organism

• Dark-field or phase-contrast microscopy in the urine

o Intermittent shedding leads to false-negative

• Culture

o Before antibiotics

o Place immediately in transport media

o To the laboratory ASAP

o Pre-treatment with furosemide may increase yield

• PCR (urine)

o Early positive

o Very sensitive

o May be positive for years after recovery

o 8% of dogs (regardless of health status) shed pathogenic leptospir

o Serology is a poor predictor of leptospiruria

• 22% sensitivity, 79% specificity

• Therapy

o Fluid therapy

• Maintain hydration

• Preserve renal function

o Antibiotics

• Ampicillin or penicillin G

• Initially IV

• Doxycycline for 2 weeks after penicillin to eliminate the carrier phase

• Decreases shedding, but may not eliminate it

• Prevention

o All serovars can potentially infect humans

o Wear gloves

o Vaccines

• Can reduce severity of the disease but do not eliminate the carrier state

• May not protect against all serovars

• Not necessary in geographic areas with low/absent risk

• The most reactogenic vaccines for the dog

• The duration of immunity is short (≤ 1 year).

• If risk of Leptospira disease is high

• Vaccines need to be given much more often than they are currently given

• 4-way lepto product

• 12 weeks, 15 weeks, 6 months, 1 year

• Then every 6 to 9 months if it remains at high risk

• Relative efficacy

• L. interrogans canicola: ≤ 75%

• L. kirshnerii grippotyphosa: ≤ 60%

• L. interrogans icterohaemorrhagiae: ≤ 90%

• L. interrogans pomoma: ≤ 60%

• Public health

o Leptospirosis can occur as either sporadic cases or in epidemics

o Infection occurs through mucosal contact with water or soil contaminated with the urine of infected animals

o Risk occupations

• Veterinarians, farmers and abattoir workers

• Recreational activities in water

References

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