(C37) Loop-mediated Isothermal Amplification PCR in Place of Modified Knott’s Test Screening Dogs for Heartworm Infection

Abstract:

Background:
The current diagnostic recommendations for Dirofilaria immitis (D. immitis) infection in dogs rely on detecting antigens primarily produced by adult females, combined with microfilariae (mf) detection tests.
Hypothesis/

Objectives:
This study aims to compare LAMP PCR and the Modified Knott's (MK) test for mf detection, used in conjunction with antigen detection tests, to screen for canine heartworm infection in shelter dogs.
Animals:
Matched whole blood samples were collected from 35 shelter dogs in Gunsan, Jeollabukdo (Republic of Korea), between June and October 2022. The study was approved by the Institutional Animal Care and Use Committee (IACUC).

Methods:
Blood samples were analyzed for the presence of mf using the MK test and for D. immitis DNA using a species-specific LAMP PCR.

Results:
Among the 10 antigen kit-positive animals, 4 (11.4%; 4/35) were found to have microfilariae morphologically identified as D. immitis. In comparison, LAMP PCR detected D. immitis DNA in two additional heartworm-positive samples, accounting for 17.1% (6/35).
Conclusion and Clinical Importance:
Although LAMP PCR was not statistically significant compared to the MK test, it detected a greater number of D. immitis cases and showed more consistency with the results of antigen detection tests. In clinical use, LAMP PCR offers advantages over the MK test, as it does not require a microscope and can be easily employed with any blood sample, similar to advanced antigen test kits, regardless of observer subjectivity. Consequently, in conjunction with antigen testing, LAMP PCR could serve as an essential screening test for D. immitis infection in canine populations.