Journal Scan: Can antibody response to Leptospira vaccine reliably predict resistance to infection?

Why they did it

Although antibody response to a Leptospira vaccine has been evaluated in an experimental setting, it has not been evaluated in client-owned dogs.

What they did  

The authors vaccinated 32 client-owned dogs with one of four commercially available Leptospira vaccines. Enrolled dogs could not have received a leptospirosis vaccine for at least one year before the study. At the time of enrollment, all but one dog had negative results for antibodies to the six Leptospira serovars tested-that dog had a titer of 1:200.

After initial vaccination, an additional vaccine was administered at 3 weeks and 52 weeks. Sera for Leptospira-antibody evaluation was collected within two to three days of each follow-up vaccine as well as at weeks 4, 7, 15, 29, and 56. Microscopic agglutination test (MAT) titers against Leptospira serovars bratislava, canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona were evaluated.

What they found

Antibody titer responses were variable among dogs and differed by serovar and vaccine. Serovars canicola, grippotyphosa, and icterohaemorrhagiae demonstrated the highest titers (1:6,400) during week 4, and at week 7, 66% of dogs still had an MAT titer ≥ 1:800 for at least one serovar. All vaccines resulted in at least some MAT titers ≥ 1:800. Antibody responses were negative in 84% of dogs one year after vaccination. None of the dogs that still had positive titers at one year had a titer ≥ 1:800.

Of note, several dogs developed titers to serovars bratislava and hardjo even though none of the vaccines used contained these serovars. This finding suggests cross-reactivity to nonvaccine serovars.

Take-home message

Antibody response is variable among dogs vaccinated against leptospirosis and suggests that antibody titers cannot reliably predict resistance to infection. The authors note that “numerous studies have shown no correlation between postvaccination titers and protection.” Recent vaccination may also increase MAT titers to ≥ 1:800 and make a clinical diagnosis of leptospirosis more challenging.

Martin LER, Wiggans KT, Wennogle SA, et al. Vaccine-associated Leptospira antibodies in client-owned dogs. J Vet Intern Med 2014;28(3):789-792.

Link to abstract: http://onlinelibrary.wiley.com/doi/10.1111/jvim.12337/abstract