Abstract

Early detection of feline dirofilariosis was achieved by ELISA testing using adult somatic (SA) and excretory/secretory (E/S) antigens. Sera from experimentally infected cats showed significantly higher IgG levels at 2 months post-infection (p.i.) when compared to sera obtained prior to infection. This difference was apparent at all serum dilutions (1:100 to 1:800) in ELISA(SA) and at all dilutions except 1:800 when tested with ELISA(E/S). Changes in specific anti-SA and anti-E/S IgG levels were found in infected cats treated with the macrolid parasiticide. ELISA(E/S) was able to detect a significant decrease in IgG levels in ivermectin treated cats at 3 months post-treatment (p.t.), compared to infected, untreated controls. However, testing with ELISA(SA) showed a significant decrease in antibody levels in treated cats only at 4 months after treatment. Sera from untreated cats recognized previously identified specific markers for feline dirofilariosis on SA (22, 26, 30 and 40 kDa) and on E/S (22 and 25 kDa) in Western blot analysis. Sera from treated cats, on the other hand, gave only weak bands or none at all, indicating a decrease in antibody concentration. These results suggest that serologic testing with ELISA is useful in the early detection of Dirofilaria immitis infection and, together with Western blot analysis, can assist in the evaluation of response to chemoprophylactic treatment of feline dirofilariosis, two aspects of prime importance in the prevention of this disease in cats.