A multidimensional analysis of the risk of infection with <i>Ehrlichia canis</i> among urban dogs in Iquitos, Peru

Abstract

<i>Ehrlichia canis</i> is a tick-borne bacterium that causes a potentially fatal disease in dogs called Canine Monocytic Ehrlichiosis. In this cross-sectional study, we used a One Health framework to identify statistical associations between <i>E. canis</i> infection in dogs and multiple dog-related, human and environmental factors in Iquitos, Peru. Due to the lack of consensus regarding the positivity threshold for <i>E. canis</i> qPCR assays, we also evaluated if the factors associated with infection remained conserved regardless of the Ct value cut-off used: Ct<35, a conservative but commonly accepted Ct <i>cut-off</i> for bacterial screening, or Ct ≤40, which has been used in several <i>E. canis</i> studies. Under the more conservative scenario, we found that the prevalence of <i>E. canis</i> among dogs was 19.6% (95% CI 15.8-23.9%). Additionally, we showed that risk factor analyses utilizing a qPCR Ct cut-off of 35 or 40 (with conventional PCR confirmation for samples with a Ct>35) yield comparable results in statistical models, although some differences should be considered. Our findings suggest that in Iquitos, Peru, interventions to prevent <i>E. canis</i> infection should prioritize dogs living in houses with corrugated iron walls. Additionally, comprehensive strategies targeting dogs that have recently traveled and incorporating neutering/spaying and widespread acaricide programs may also prove beneficial. We also discuss the challenges encountered during molecular testing for <i>E. canis</i> detection, highlighting the broader difficulties of studying poorly understood intracellular pathogens in Global South countries.