Immunization with a recombinant subunit OspA vaccine markedly impacts the rate of newly acquired Borrelia burgdorferi infections in client-owned dogs living in a coastal community in Maine, USA.

Andrew K Eschner,Kristen Mugnai

doi:10.1186/s13071-015-0676-x

Abstract

BackgroundIn North America, Borrelia burgdorferi is the causative bacterial agent of canine Lyme borreliosis and is transmitted following prolonged attachment and feeding of vector ticks, Ixodes scapularis or Ixodes pacificus. Its prevention is predicated upon tick-avoidance, effective on-animal tick control and effective immunization strategies. The purpose of this study is to characterize dogs that are newly seropositive for Borrelia burgdorferi infection in relation to compliant use of a recombinant OspA canine Lyme borreliosis vaccine. Specifically, Preventive Fractions (PF) and Risk Ratios (RR) associated with the degree of vaccine compliancy (complete versus incomplete) are determined.Methods6,202 dogs were tested over a five year period in a single veterinary hospital utilizing a non-adjuvanted, recombinant OspA vaccine according to a 0, 1, 6 month (then yearly) protocol. Rates of newly acquired “Lyme-positive” antibody test results were compared between protocol compliant and poorly compliant (incompletely and/or non-vaccinated) dogs.ResultsOver the five-year span, one percent (range 0.39 - 1.3) of protocol compliant vaccinated, previously antibody negative dogs became seropositive for infection. Approximately twenty-one percent (range 16.8 – 33.3) of incompletely vaccinated dogs became positive for infection-specific antibodies. The Preventative Fraction for testing positive for antibodies specific for infection with Borrelia burgdorferi in any given year based on optimal vaccine compliance was, on average, 95.3% (range 93.29 - 98.08). The Risk Ratio for becoming infected with Borrelia burgdorferi antibodies in any given year if vaccine non-compliant was 21.41 (range 14.9 – 52.1). There was a high statistically significant relationship (p = <0.0001) in the observed data in terms of vaccination protocol compliance and the probability of Borrelia burgdorferi infection in each of the five years under study.ConclusionsThe recombinant outer surface protein A (rOspA) vaccine for dogs is highly effective in preventing new seropositive cases of Borrelia burgdoferi infection over a five-year period in dogs living in an endemic area. Dogs that were vaccine protocol-compliant were significantly less likely to become infected (as indirectly assessed by antibody) with the agent of canine Lyme borreliosis as measured by Preventive Fraction and Risk Ratio calculations.

Highlights

In North America, Borrelia burgdorferi is the causative bacterial agent of canine Lyme borreliosis and is transmitted following prolonged attachment and feeding of vector ticks, Ixodes scapularis or Ixodes pacificus
Five placebo-controlled laboratory studies pertaining to commercialized whole-cell Lyme borreliosis bacterins and recombinant Outer-surface protein A (OspA) vaccines for dogs have been published [6-10]
In an effort to decrease the adverse reaction profile and remedy the occasional diagnostic conundrums posed by whole cell bacterins for Lyme borreliosis, a Type I recombinant OspA subunit extract was licensed and marketed for canine use in the United States in 1996

Summary

Introduction

In North America, Borrelia burgdorferi is the causative bacterial agent of canine Lyme borreliosis and is transmitted following prolonged attachment and feeding of vector ticks, Ixodes scapularis or Ixodes pacificus. In an effort to decrease the adverse reaction profile and remedy the occasional diagnostic conundrums posed by whole cell bacterins for Lyme borreliosis, a Type I recombinant OspA (rOspA) subunit extract was licensed and marketed for canine use in the United States in 1996. This vaccine was the first Lyme disease vaccine to be licensed by the USDA demonstrating a 1-year duration of immunity (DOI) after use of a natural tick challenge model [9]. In 2000, a randomized, placebo-controlled study explored the effectiveness of the recombinant OspA vaccine (Recombitek® Lyme, Merial) and demonstrated that non-adjuvanted recombinant OspA completely prevented B. burgdorferi infection in vaccinated dogs [10]

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