Utility of adult antigens of Dirofilaria immitis for the early detection of dirofilariosis and for the evaluation of chemoprophylactic treatment in experimentally infected cats

Early detection of feline dirofilariosis was achieved by ELISA testing usin g adult somatic (SA) and excretory/secretory (E/S) antigens. Sera from expe rimentally infected cats showed significantly higher IgG levels at 2 months post-infection (p.i.) when compared to sera obtained prior to infection. T his difference was apparent at all serum dilutions (1:100 to 1:800) in ELIS A(SA) and at all dilutions except 1:800 when tested with ELISA(ES). Changes in specific anti-SA and anti-E/S IgG levels were found in infected cats tr eated with the macrolid parasiticide. ELISA(ES) was able to detect a signif icant decrease in IgG levels in ivermectin treated cats at 3 months post-tr eatment (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. Se ra from treated cats, on the other hand, gave only weak bands or none at al l, indicating a decrease in antibody concentration. These results suggest t hat serologic testing with ELISA is useful in the early detection of Dirofi laria immitis infection and, together with Western blot analysis, can assis t in the evaluation of response to chemoprophylactic treatment of feline di rofilariosis, two aspects of prime importance in the prevention of this dis ease in cats. (C) 1999 Elsevier Science B.V. All rights reserved.