Molecular Detection of Dirofilaria immitis Specific Gene from Infected Dog Blood Sample Using Polymerase Chain Reaction

Background: Dirofilaria immitis, a filarial nematode, is the most important parasiteaffecting dogs, causing cardiopulmonary dirofilariasis. Current diagnostic tools for detecting D. immitis include morphological assays, antigen detection, and X-ray. Herein, we developed a method for the molecular detection of D. immitis in blood using polymerase chain reaction (PCR). Methods: The study was conducted at Eulji University, Republic of Korea in 2016. To detect D. immitis-specific gene regions, we aligned the cytochrome c oxidase subunit I (COI) genes of seven filarial nematodes and designed primers targeting the unique region. We used dog glyceraldehyde-3-phosphate dehydrogenase (GAPDH)- targeted primers as the internal control. We conducted PCR-amplified genomic DNA from canine blood samples. The products were confirmed by sequencing. Results: Gene alignment revealed a D. immitis COI-specific gene region, and the activity of designed primers was confirmed by PCR and sequencing. Plasmid DNA made from the PCR products was a positive control. The limit of detection for our method was 50 copies. The D. immitis COI and dog GAPDH genes could be discriminated from blood samples simultaneously. Conclusion: This study provides a method for highly specific and sensitive molecular diagnosis of D. immitis used as a diagnostic and therapeutic tool from the early stage of infection.