Abstract: Background - Canine heartworm disease continues to be diagnosed in the United States, with positive tests numbering more than 100,000 / year (according to the Companion Animal Parasite Council) nationally. To date, much of the peer reviewed literature on canine heartworm infection has focused on epidemiologic and prevalence data, severe clinical presentations, and parasite resistance. Hypothesis/Objectives - The objective of this study was to examine longitudinal outcomes in dogs that tested positive and underwent therapy for heartworm infection within primary care hospitals. Animals - Privately owned dogs presenting to Banfield Pet Hospital were included in the study. Dogs testing positive for heartworms (via antigen test) were identified as cases and a population of negative controls was identified. Methods - Retrospective, case-control study with dogs identified via medical record search. In this system, longitudinal data is available for individual dogs, allowing long term analysis. Analysis on structured diagnostic codes pertaining to right and left sided cardiac disease and relative risk of outcomes was performed. Results – Dogs positive for heartworm infection were found to have increased relative risk (RR) for right heart failure (RR 3.59, 95% C.I. 2.64-4.86), left heart failure (1.83, 95% C.I. 1.51-2.22), and cardiomyopathy (2.79, 95% C.I. 1.71-4.57) compared to negative controls. All p values were significant at p< 0.0001 (Table 1). Conclusions and clinical importance – This analysis describes the longitudinal clinical outcomes of dogs with heartworm infections and provides data driven evidence to demonstrate the importance of disease prevention.
