Comparison of serological methods and blood culture for detection of Trypanosoma cruzi infection in raccoons (Procyon lotor)

The indirect immunofluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) were compared with blood culture for the detection of Trypanosoma cruzi infection in 83 raccoons (Procyon lotor) trapped in 4 counties of southeast Georgia. Both IFAT and ELISA detected 24 of 25 culture-positive samples (96% sensitivity). Cultures from 25 raccoons (30%) were positive for epimastigotes, whereas a total of 50 raccoons (60%) was seropositive by either the IFAT or ELISA. Forty-five of 83 serum samples (54%) were positive for anti-T. cruzi antibodies with the ELISA, and 47 were IFAT positive (57%). Forty-two of the 50 seropositive raccoons (84%) were seropositive by both tests. Endpoint titers of IFAT-positive samples were determined by testing doubling dilutions from 1:40 to 1:1280. High titers of 640 and 320 were observed for 4 raccoons trapped in 1 county (St. Catherines Island, Liberty County) and titers of 160 for 1-2 raccoons from each of the 4 counties sampled. IFAT titers and ELISA optical density values were positively correlated. Both serological tests have a high sensitivity and should be excellent tools for studying the prevalence of T. cruzi in wildlife populations.