Abstract
Canine heartworm disease, caused by Dirofilaria immitis (Leidy, 1856), is a parasitic roundworm infection common in tropical regions. It impacts animals and humans, residing in pulmonary arteries and causing severe lung damage and significant health risks. Although well-studied globally, canine heartworm infections remain uninvestigated in Mongolia. This study aimed to detect microfilariae and identify D. immitis in dogs, contributing to understanding the presence of heartworm disease in Mongolia's urban areas. Hematologic samples (n = 180) were collected from owned and unowned dogs across six districts in urban Ulaanbaatar, Mongolia, using EDTA tubes. Whole blood samples were tested for microfilaria and D. immitis DNA via thin blood smear, the modified Knott's test, and PCR. A commercially available kit was used to detect canine heartworm antigen in blood. Two dogs were confirmed to have D. immitis infections based on comprehensive tests. The D. immitis 5.8S-ITS2-28S gene sequence from Mongolian dog matched sequences from other countries and clustered similarly in phylogenetic analyses. This is the first molecular detection and identification of D. immitis in Mongolian dogs. © 2025 Elsevier B.V., All rights reserved.