A Taq-Man-based multiplex quantitative PCR for the simultaneous detection and quantification of Angiostrongylus vasorum, Crenosoma vulpis, and species of respiratory capillarids in canids

In recent years, Angiostrongylus vasorum, Crenosoma vulpis, Eucoleus aerophilus (syn. Capillaria aerophila) and Eucoleus boehmi (syn. Capillaria boehmi), commonly referred to as canine lungworms, have gained a growing interest worldwide as the result of their geographical expansion. Each of these nematode species differs considerably in its biology and pathogenicity. Despite their impact on dogs’ health, these parasites are often underdiagnosed owing to diagnostic challenges. Here, we describe the development and validation of a Taq-Man-based multiplex quantitative PCR (qPCR) for the simultaneous detection of the main species of canine lungworms in faeces of infected dogs. Using 10-fold serial dilutions of synthetic gene block fragments containing individual sequence targets of each lungworm species, the analytical sensitivity of the assay ascertained was 1.84 ng/μl for A. vasorum, 3.08 ng/μl for C. vulpis and 0.79 ng/μl for Eucoleus spp. The sensitivity of the assays and their ability to detect mixed species infections were compared with microscopy-based techniques (faecal floatation and Baermann technique) applied to faecal samples submitted for lungworm testing through an accredited diagnostic laboratory at the Institute of Parasitology, University of Zurich, Switzerland, and from community dogs as part of a research project on canine endoparasites in Cambodia. The multiplex qPCR displayed high diagnostic sensitivity (42/46, 91.3%; 95% Confidence Interval (CI): 79.1–97.1%) and a diagnostic specificity of 100% (45/45, 95% CI: 90.6–100%), and was able to detect 42.9% additional mixed lungworm species infections compared with microscopy-based methods. Kappa statistics showed substantial agreement between the qPCRs and microscopy for mixed infections (κ = 0.72, 95% CI: 0.4–1) and Eucoleus spp. (κ = 0.65, 95% CI: 0.45–0.85) and almost perfect agreement for C. vulpis (κ = 0.85, 95% CI: 0.63–1) and A. vasorum (κ = 0.92, 95% CI: 0.84–1).

This multiplex qPCR enables timely, accurate, and sensitive diagnosis of canine lungworm species in faecal samples and can be used to monitor the geographical distribution and emergence of these parasitic species, globally.