Diagnostic and clinical implications of a nested PCR specific for ribosomal DNA of the feline lungworm Aelurostrongylus abstrusus (Nematoda, Strongylida).

Aelurostrongylus abstrusus (Nematoda, Strongylida, Metastrongyloidea) is a cosmopolitan parasite of cats and causes severe respiratory distress. Information on the biology and epidemiology of feline aelurostrongylosis is fragmentary, mainly due to the limits inherent in the classical diagnosis. In the present work, a two-step nested PCR based on the use of genetic markers in the second internal transcribed spacer (ITS2) of ribosomal DNA was established for A. abstrusus in different biological samples. Characterization of the ITS2 (321 bp of length) revealed a G+C content of 39.5%. To exploit the sequence difference between the ITS2 of A. abstrusus and those of other common feline endoparasites, specific primers were designed and tested by PCR for their specificities and sensitivities. The PCR assay was validated on a panel of fecal (i.e., feces, flotation supernatant, and Baermann sediment) and pharyngeal swab samples from cats with known histories of lungworm infections, and it showed a specificity of 100% and a sensitivity of up to 96.6%. Also, the nested PCR was able to identify cats that were actually infected but that tested negative by the classical diagnostic methods. This PCR method was shown to be a powerful tool for the molecular diagnosis of feline aelurostrongylosis, overcoming the constraints of the classical diagnosis. The implications of such a molecular tool for further bioepidemiological studies of both intermediate and definitive hosts have been discussed.