Detección molecular con la técnica de PCR en un solo paso para dirofilaria immitis en perros del cantón Machala, Santa Rosa y cantón Huaquillas, El Oro, Ecuador

Abstract

Canine cardiopulmonary dirofilariasis caused by Dirofilaria immitis is an emerging zoonosis of increasing relevance in tropical and coastal regions. This study aimed to determine the presence of the parasite in dogs from the cantons of Machala, Santa Rosa, and Huaquillas, in El Oro Province, Ecuador, using a combined approach of immunodiagnostics, PCR, and phylogenetic analysis. A total of 40 dogs with compatible clinical or epidemiological backgrounds were evaluated using a rapid immunochromatographic (IC) antigen test as an initial screening tool. Of these, 24 dogs (60%) tested positive by IC; however, endpoint PCR targeting the mitochondrial COI gene confirmed infection in only 10 cases (41.7%), revealing potential false-positive serological reactions. Chi-square statistical analysis showed a significant association between PCR results and canton of origin (p < 0.001), with Machala exhibiting the highest proportion of positive cases. No significant relationship was observed with sex (p = 1.00) or individual age (p = 0.212). Sanger sequencing of PCR amplicons and comparison with GenBank sequences confirmed D. immitis with 100% identity. Phylogenetic analysis demonstrated low genetic diversity, clustering within haplotypes shared with strains reported from Europe, North America, and Asia. These findings confirm active circulation of D. immitis in El Oro Province and highlight the need for surveillance and control strategies under a One Health framework. Furthermore, the study demonstrates the value of molecular diagnostics as a complementary tool to improve epidemiological accuracy and reduce false-positive outcomes.