Cross-reactions of sera from dogs infected with Angiostrongylus vasorum in commercially available Dirofilaria immitis test kits

Background: Dirofilaria immitis and Angiostrongylus vasorum are both important potentially fatal canine nematodes with overlapping endemic areas, especially in Europe. The preadult and adult stages of both species are living in the Arteria pulmonalis and the right heart, and diagnostically detectable circulating parasite antigens have been demonstrated for both species. For the detection of D. immitis infections, a variety of commercial tests have been developed, however, they have not been evaluated for cross-reactions against circulating antigens of A. vasorum. Methods: In this study, potential cross-reactions of sera from 16 dogs, which were experimentally infected with A. vasorum and which had circulating antigens as confirmed by a species-specific ELISA, were evaluated for the detection of A. vasorum antigen in six commercially available D. immitis test kits. Results: In three fast tests (Witness (R) Dirofilaria, SensPERT (R) Canine Heartworm, SNAP (R) 4Dx (R) Plus), all sera were negative. One fast membrane ELISA (SNAP (R) HTWM RT Test) was positive with four sera (25%), and one serum delivered a non-valid result twice. In the PetChek (R) HTWM PF Test, depending on the interpretation protocol, 5 or 8 dogs (31.2 - 50%) were positive. With the DiroCHEK (R)-ELISA, a single A. vasorum-infected dog (6.2%) tested positive. Conclusions: Due to potential cross-reactions with A. vasorum in commercially available test kits for the detection of D. immitis antigen, the simultaneous use of highly specific diagnostic methods for the differentiation of these two canine heart worms is recommended.