Diagnostic challenges for Aelurostrongylus abstrusus infection in cats from endemic areas in Italy

Background The lungworm Aelurostrongylus abstrusus infects wild and domestic feline species worldwide and is considered a primary respiratory parasite of cats. Definitive diagnosis is based on identification of first stage larvae (L1s) released in faeces approximately 5 to 6 weeks after infection. More recently, serology has been shown to be a diagnostic alternative for A. abstrusus infection in cats. The present study was aimed at evaluating the diagnostic performance of serological antibody detection compared to faecal examination for A. abstrusus infection in a population of cats with known infection status from endemic areas in Italy and to identify factors (larval scores, age, co-infections with other helminths) that may influence test sensitivity and specificity. Methods All cats resulting positive in the Baermann technique (n=78) were tested with the A. abstrusus ELISA An additional 90 serum samples from cats living in three geographical areas with infection prevalence greater than 10%, but that resulted negative in Baermann, were also tested. Results Among 78 cats copromicroscopically positive for L1s of A. abstrusus (Group 1), 29 (37.2%) were seropositive in ELISA. Of the 90 cats from Group 2 (cats living in three geographical areas in Italy with A. abstrusus prevalence greater than 10%, but negative in Baermann examination), 11 (12.2%) were positive in ELISA. The overall seroprevalence was 23.8%. There was no statistical difference either between average optical density (OD) values of cats excreting >100 L1s vs. cats excreting P value = 0.3247) or comparing the OD values with age of infected cats. Few Baermann-negative cats positive for Toxocara cati or hookworms were seropositive, supporting lack of cross reactivity to these nematodes. Conclusions Results from the present study suggest that relying solely on faecal examination may underestimate prevalence of A. abstrusus infection in cats and that field surveys based on antibody detection is useful for establishing true prevalence of infected and/or exposed animals.