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. 2017 Nov 9;10(Suppl 2):476.
doi: 10.1186/s13071-017-2444-6.

Heat treatment and false-positive heartworm antigen testing in ex vivo parasites and dogs naturally infected by Dirofilaria repens and Angiostrongylus vasorum

Luigi Venco  1 , Simone Manzocchi  2 , Marco Genchi  3 , Laura H Kramer  3
Affiliations

Heat treatment and false-positive heartworm antigen testing in ex vivo parasites and dogs naturally infected by Dirofilaria repens and Angiostrongylus vasorum

Luigi Venco et al. Parasit Vectors. .

Abstract

Background: Heartworm antigen testing is considered sensitive and specific. Currently available tests are reported as detecting a glycoprotein found predominantly in the reproductive tract of the female worm and can reach specificity close to 100%. Main concerns regard sensitivity in the case of light infections, the presence of immature females or cases of all-male infections. Research and development have been aimed at increasing sensitivity. Recently, heat treatment of serum prior to antigen testing has been shown to result in an increase in positive antigen test results, presumably due to disruption of natural antigen-antibody complexes. Cross-reactions in dogs with both natural and experimental infections with Angiostrongylus vasorum and Spirocerca lupi have been reported, but cross-reactions with other helminths have not been extensively studied. In order to evaluate potential cross-reactivity with other canine and feline parasites, two studies were performed. Study 1: Live adults of Dirofilaria immitis, Dirofilaria repens, Toxocara canis, Toxocara cati, Dipylidium caninum, Taenia taeniaeformis and Mesocestoides spp. larvae were washed and incubated in tubes with saline solution. All worms were alive at the time of removal from the saline. Saline solutions containing excretory/secretory antigens were then tested for heartworm with six different, commercially available antigen tests. All results were evaluated blind by three of the authors. Study 2: Sera from dogs with natural infections by A. vasorum or D. repens, living in areas free of heartworm disease, were tested with the same tests before and after heat treatment (103 °C for 10 min).

Results: Results suggest that antigens detected by currently available tests are not specific for D. immitis. They may give positive results through detection of different parasites' antigens that are normally not released into the bloodstream or released in a low amount and/or bound to antibodies. Tests may even detect antigens released by male D. immitis adult worms. D. repens appears to release more detectable antigens than the other worms studied.

Conclusions: Cross-reaction with A. vasorum and D. repens does occur in the field and could potentially occur with other helminths. Heat treatment decreases specificity by enhancing cross-reactivity.

Keywords: Antigen tests; Cross-reactivity; Dirofilaria spp..

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Conflict of interest statement

Ethics approval and consent to participate

For these studies, no ethics approval was requested as no animals were involved in clinical-diagnostic procedures other than requested for their health and with owner permission. T. canis, T. cati, D. caninum and T. taeniaeformis were recovered following humane euthanasia of pets for reasons unrelated to parasitic infections, in which necropsy was allowed or requested by the owners.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

    1. Lee AC, Bowman DD, Lucio-Forster A, Beall MJ, Liotta JL, Dillon R. Evaluation of a new in-clinic method for the detection of canine heartworm antigen. Vet Parasitol. 2011;177(3-4):387–391. doi: 10.1016/j.vetpar.2010.11.050. - DOI - PubMed
    1. Atkins CE. Comparison of results of three commercial heartworm antigen test kits in dogs with low heartworm burdens. J Am Vet Med Assoc. 2003;222(9):1221–1223. doi: 10.2460/javma.2003.222.1221. - DOI - PubMed
    1. Courtney CH, Zeng Q. Comparison of heartworm antigen test kit performance in dogs having low heartworm burdens. Vet Parasitol. 2001;96(4):317–322. doi: 10.1016/S0304-4017(01)00374-0. - DOI - PubMed
    1. Schnyder M, Deplazes P. Cross-reactions of sera from dogs infected with Angiostrongylus vasorum in commercially available Dirofilaria immitis test kits. Parasit Vectors. 2012;5:258. doi: 10.1186/1756-3305-5-258. - DOI - PMC - PubMed
    1. Aroch I, Rojas A, Slon P, Lavy E, Segev G, Baneth G. Serological cross-reactivity of three commercial in-house immunoassays for detection of Dirofilaria immitis antigens with Spirocerca lupi in dogs with benign esophageal spirocercosis. Vet Parasitol. 2015;211(3-4):303–305. doi: 10.1016/j.vetpar.2015.06.010. - DOI - PubMed

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