Veterinary Public Health

Leptospirosis in Dogs - Case Definition

About This Case Definition

This case definition is used to evaluate and categorize cases of leptospirosis reported in dogs to the Los Angeles County Department of Public Health. It was developed by public health veterinarians by reviewing published literature and reported cases of leptospirosis in LA County dogs. Earlier case reports of this disease were reviewed and a few reclassified to meet this 2015 case definition.

Learn more about animal disease surveillance in LA County, and about cases of leptospirosis in dogs in LA County.

2016: For the purposes of this case definition, positive lepto ELISA antibody results are considered to be similar to low positive (i.e. 1:400) antibody titers.

Case Definition - Leptospirosis in Dogs - 2015

Confirmed

  • 4-fold change in antibody titer to at least one serovar (samples drawn 2-4 weeks apart) in a dog that did not receive a Leptospira vaccine in 6 months before testing, or
  • PCR positive urine or blood sample, or
  • Silver stain or immunostaining positive histology, or
  • Positive silver or immunostaining of urine sediment, or
  • Isolation of Leptospira organisms by culture of urine or tissue

Probable

Compatible clinical findings PLUS:

  • Positive antibody titer with at least one serovar ≥ 1:800 (dog that did not receive a vaccine in 6 months before testing), or
  • Antibody titer ≥ 1:6400 in dog with unknown vaccine history, or
  • 4-fold change in antibody titer to at least one serovar (samples drawn 2-4 weeks apart) in a dog with unknown vaccine history

Suspected

Compatible clinical findings PLUS:

  • Positive antibody titer with at least one serovar ≥ 1:400 in an unvaccinated dog, or
  • Titer to at least one serovar ≥ 1:800 in a dog with an unknown vaccine history

Not a case

  • Does not meet the case definition of Confirmed, Probable or Suspected, or
  • No compatible clinical findings AND antibody titer < 1:4 (i.e. incidental low positive titer)

Compatible clinical findings

At least three of the following: Azotemia, PU/PD, oliguria / anuria, fever, elevated liver enzymes (ALT, AST, ALP), icterus / ↑ total bilirubin, vomiting, anorexia, widespread petechiae, uveitis, pulmonary hemorrhage, abortions.

Exposure location

In general, cases are considered to be "Other" or "Unknown" unless the history indicates no travel outside of area.

  • UNKNOWN - No travel history or less than 1 month of history available.
  • LA COUNTY - No travel outside of LA County in month before onset
  • SO CAL - No travel outside of southern California in month before onset
  • OTHER - Dog traveled or lived outside of southern California in month before onset

For the purpose of this case definition Southern California includes the following counties: Los Angeles, Orange, San Luis Obispo, Kern, Santa Barbara, Ventura, San Bernardino, Riverside, San Diego & Imperial.

Rationale for surveillance in animals

Dogs with leptospirosis can directly transmit it to people through urine. Dog cases are also sentinels. Cases indicate that the bacteria is in wildlife or water in the dog's environment. Humans in same environment may also be exposed. Epidemiological data is valuable to LA County veterinarians to guide decisions on vaccination, testing and treatment.

References

  • Barr SC et al (2005). Serologic responses of dogs given a commercial vaccine against Leptospira interrogans serovar pomona and Leptospira kirschneri serovar grippotyphosa. Am J Vet Res 66(10):1780-1784.
  • Greene, Infectious diseases of the dog and cat. 4th ed. Elsevier Saunders. St. Louis, MO. 2012; 431-447.
  • Sykes JE, Hartmann K, Lunn KF, et al. 2010 ACVIM Small Animal Consensus Statement on Leptospirosis: Diagnosis, Epidemiology, Treatment, and Prevention. JVIM 2011; 25: 1–13. doi: 10.1111/j.1939-1676.2010.0654.x
  • Martin et al (2014) Vaccine-associated Leptospira Antibodies in Client-Owned Dogs. J Vet Intern Med 28:789-792
  • National Notifiable Diseases Surveillance System (NNDSS) Leptospirosis 2013 Case Definition
  • Standard Interpretive Comments for Leptospirosis MAT titers from Antech and IDEXX Animal Diagnostic Laboratories, 2014. IDEXX interpretive comment states PCR positives indicate DNA from pathogenic Leptospira. Antech interpretive comment states a positive PCR result supports a diagnosis of acute leptospirosis.