Lyme disease is endemic to some parts of North America, and is an emerging disease in others. Although tick preventives are available, vaccination is an increasingly common though controversial method used in the prevention of canine Lyme infection; reported efficacies of canine Lyme vaccines are highly variable, ranging from 50% to 100%. The objective of our research was as follows: to determine the efficacy of vaccines for Borrelia burgdorferi in North American dogs by comparing vaccinated dogs to those not receiving the vaccine. We used a systematic review and meta-analysis to address this objective.
Monovalent and multivalent vaccines were considered eligible interventions. Our main outcome of interest was the reduction of clinical illness following exposure to B. burgdorferi. Outcome data were extracted as a binary outcome for the following clinical signs (assessed separately): lameness, anorexia, pyrexia, depression, lymphadenopathy. Experimental and analytical observational studies were considered eligible for inclusion. In addition to grey literature searches, the following electronic databases were searched with no language restrictions: MEDLINE, Web of Science, CAB Abstracts. The last search was performed on November 29, 2016.
Thirteen challenge trials and three observational studies were identified as eligible, and twelve challenge trials contained sufficient data to be included in our meta-analysis. A meta-analysis could not be performed for observational studies due to an insufficient number of studies. None of the challenge trials assessed lymphadenopathy, but for each of the remaining four clinical signs a separate random effects meta-analysis was performed. With the exception of anorexia, all summary odds ratios were less than the null value of 1. Overall, the findings of our meta-analysis suggest that North American Lyme vaccines reduce the odds of clinical illness in dogs following exposure to B. burgdorferi. However, these results should be interpreted with caution since a number of issues related to small sample size, study quality, and publication bias were identified. No experimental field trials were identified, highlighting a major gap in the literature on this topic. Future studies should focus on larger sample sizes in field conditions.
Department of Population Medicine, University of Guelph
Thursday, June 14
5:30 PM – 5:45 PM
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