• Open Access

Effects of Recent Leptospira Vaccination on Whole Blood Real-Time PCR Testing in Healthy Client-Owned Dogs


  • This study was performed primarily at the Cornell University, College of Veterinary Medicine. PCR and MAT were also performed at IDEXX Laboratories in Sacramento, CA and North Grafton, MA, respectively. The study was partially supported by a grant from IDEXX Laboratories, and was presented in poster form at the 2010 ACVIM Forum, Anaheim, CA.

Corresponding Author: R.E. Goldstein, Department of Clinical Sciences, CVM, Cornell University, Ithaca, NY 14853; e-mail: Rg225@cornell.edu.



Bacterin-based canine Leptospira vaccines could present a challenge for the use of whole blood real-time polymerase chain reaction (PCR) as a diagnostic tool. Recent vaccination could induce positive results if the targeted DNA fragment is present within the vaccine and in the blood of the recently vaccinated dog.


The objective of this study was to assess whether 2 available 4-serovar vaccines induce a positive real-time PCR reaction in the blood of healthy recently vaccinated dogs.


Twenty healthy dogs.


This was a prospective study. Dogs were assigned to 1 of 2 vaccine groups. Both vaccines were culture-based and include Leptospira interrogans serovars Pomona, Canicola, and Icterohaemorrhagiae and Leptospira kirschneri serovar Grippotyphosa. Whole blood for real-time PCR and serum for the microscopic agglutination test (MAT) were collected prior to and 3 and 7 days after vaccination and weekly thereafter for 8 weeks. Two real-time PCR tests targeting 2 different genes were performed independently in a blinded fashion.


Both Leptospira vaccines produced positive real-time PCR reactions when assayed undiluted or diluted 1 : 100 in canine blood. However, blood samples drawn from all dogs at all time points after vaccination were negative on PCR. All dogs developed MAT titers.

Conclusions and Clinical Importance

Recent vaccination with 2 commercially available vaccines does not interfere with the use of real-time PCR for the identification of acute Leptospira infection in dogs.