Development of Dirofilaria immitis adult worms in NSG mice, detection of parasite-derived microRNA and comparative analysis of laboratory isolates

Global efforts to control heartworm disease are challenged by increasing drug resistance and inadequate early detection methods, which hinder the effective diagnosis and treatment of Dirofilaria immitis infection. This study presents an in vivo model for investigating D. immitis development and host-parasite interactions. The growth and migration of the D. immitis JYD-34 isolate were analyzed in immunodeficient NSG mice over 177 days, revealing parasite migration to the heart and lungs, which mirrors infection dynamics in the natural canine host. Pathophysiological examination of host tissues revealed early adult-stage worms elicited minimal inflammation. However, with chronicity, mild pulmonary hemosiderin accumulation was observed. Plasma profiling identified 31 D. immitis-specific microRNAs (miRNAs), 22 of which have also been detected in D. immitis infected dogs. Infection resulted in nine differentially expressed murine miRNAs, providing insights into host-parasite interactions and potential diagnostic biomarkers. Comparative analysis of five D. immitis isolates revealed distinct growth dynamics and cardiopulmonary migration patterns, enhancing our understanding of isolate-specific variation. Overall, this study supports the use of NSG mice as a practical and reproducible in vivo model for heartworm disease to answer fundamental questions regarding parasite development, host interaction and inter-isolate variation, with broad applications in developing novel drugs and diagnostics.