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

Abstract

Background: 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.Objectives: 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.Animals: Twenty healthy dogs.Methods: 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.Results: 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.

Orchitis and balanoposthitis in a dog withLeptospira interrogansserovar Canicola in Southern California

“…PCR, which detects leptospiral DNA, has the potential advantage for diagnosis early in the course of illness, when serologic tests are negative or in dogs that possess residual antibody after vaccination 36. Leptospires are generally found in blood for the first 10 days after infection and thereafter in urine 37.…”

A comparison of two real-time polymerase chain reaction assays using hybridization probes targeting either 16S ribosomal RNA or a subsurface lipoprotein gene for detecting leptospires in canine urine

“…Despite the satisfactory data regarding in vitro accuracy, data regarding clinical cases and the use of qPCR, using both rrs and LipL32 targets in natural canine infections, is scarce. 22 This is also true when interpreting the findings in those studies that used different qPCR assays when investigating the molecular epidemiology of leptospirosis in dogs. 27 Ideally, the use of the rrs gene, which is largely used for classification purposes, 10,23 has the advantage of a wider database of nucleotide sequences for in silico validation.…”

“…37 A hydrolysis probe-based qPCR assay targeting the 16S ribosomal RNA (rrs) gene has also been validated in humans. 28,30 This assay has gained popularity over time and has also been adopted for use in dogs 22 as the assay has been validated for all pathogenic leptospires, including those known to infect dogs.…”

Leptospirosis in dogs and cats: new challenges from an old bacteria

“…The current recommendation is that PCR and the MAT are used in conjunction while further research is performed on the sensitivity and specificity of PCR testing (Schuller and others 2015). Vaccination does not result in positive PCR results (Midence and others 2012). …”