Aspergillus qPCR testing on nasal swab: A useful tool for diagnosis and follow‐up of sinonasal aspergillosis in dogs?

Polymerase chain reaction (PCR) testing either for Aspergillus.spp or for Aspergillus fumigatus is now available; however, the interest of such tests in the diagnosis of canine sinonasal aspergillosis (SNA) has not yet been assessed. The aim of this study was to evaluate the presence of fungal material using qPCR targeting Aspergillus.spp (PanAsp) and A. fumigatus (Aspfum) in samples obtained from nasal cavities of dogs with various nasal diseases and healthy dogs.

In SNA dogs, Aspfum and PanAsp were positive in 13/20 and 14/20 dogs with a mean cycle threshold (Ct) of 30.6 [range 23,2 ‐ 33,3] and 28.3 [24,3 ‐ 34,5], respectively. The PanAsp was also positive in 3 non‐SNA dogs: one with cured SNA, one with LPR and one with nasal tumor, but at very low load (Ct>33). Results between both qPCR were highly correlated (r = 0.8, P < 0.01). For Aspfum and PanAsp, the sensitivity was 65% and 70% and the specificity was 100% and 94%, respectively.

Aspfum qPCR test on deep blinded nasal swabs appears highly specific but only moderately sensitive to diagnose canine SNA. In some dogs fungal plaques are exclusively found in the frontal sinus and are probably not reached by blinded sampling. Since A. fumigatus is the most common etiological agent of canine SNA (96.7% of isolates), Aspfum testing appears appropriate; however, PanAsp testing is a non‐negligible tool to detect the small percentage of SNA cases related to other Aspergillus species. Results also show that healthy predisposed dogs do not seem to be carriers and confirm that A. fumigatus does not appear to have a major role in LPR. The negative results found in cured SNA dogs show a good correlation with clinical and rhinoscopic findings.

In conclusion, Aspfum and/or PanAsp (qPCR testing) on deep nasal blinded swabs can be useful for the detection of SNA at diagnosis and after cure.