A Comparison of Copromicroscopic and Molecular Methods for the Diagnosis of Cat Aelurostrongylosis

Simple Summary Feline aelurostrongylosis is a worldwide distributed parasitic disease of domestic cats caused by the nematode Aelurostrongylus abstrusus. Cats may have a subclinical infection with this parasite or may show signs that overlap with those of many other respiratory conditions of cats, either parasitic or not. The diagnosis of feline aelurostrongylosis currently relies on fecal examinations, though this approach has some limits that can be overcome by innovative molecular techniques. Therefore, the present study has investigated the diagnostic reliability of a PCR assay performed on different samples collected from cats from Italy and Greece. The results of the study confirmed that PCR is highly sensitive and specific for the diagnosis of A. abstrusus infections in domestic cats. The gold standard method for the diagnosis of cat aelurostrongylosis is the detection of Aelurostrongylus abstrusus first stage larvae with the Baermann's examination. Nevertheless, molecular assays have shown higher diagnostic performances compared to copromicroscopy. This study evaluated the usefulness of an A. abstrusus species-specific PCR on different biological samples collected in clinical settings from 100 privately-owned cats in Italy (n. 60) and Greece (n. 40). A fecal sample was collected from each animal and a pharyngeal swab was also obtained for cats from Italy. All stool samples were subjected to flotation and Baermann's test. The cats were categorized in three groups based on the results of copromicroscopy, i.e., Group A (n. 50 cats with A. abstrusus infection regardless of positivity for other helminths), Group B (n. 25 cats negative for A. abstrusus but positive for at least one of any other helminth), Group C (n. 25 cats negative for any helminth). DNA was extracted from individual aliquots of feces, flotation supernatant, Baermann's sediment and the pharyngeal swab and then subjected to a PCR specific for A. abstrusus. At least one fecal aliquot or the pharyngeal swab scored positive by the A. abstrusus-specific PCR for 48/50 (96%) cats enrolled in Group A; in particular, 38/50 (76%), 35/50 (70%), 41/50 (82%) and 21/25 (84%) DNA extracts from feces, flotation supernatant, Baermann's sediment and pharyngeal swabs were positive by PCR. These results confirm that molecular tools are highly sensitive and specific and indicate that pharyngeal swabs are the most suitable sample for molecular analysis in clinical settings.