Abstract: Background- Two positive serologic tests are recommended to confirm T. cruzi infection in humans. Serologic diagnosis remains challenging in dogs. Objective- To evaluate five serologic test results and blood PCR for T. cruzi. Animals- Eighteen, client-owned dogs Methods- Observational, exploratory study evaluating two tests performed at reference/commercial laboratories including indirect fluorescent antibody (IFA) at Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL, College Station, TX) and ELISA at VRL Laboratories (San Antonio, TX), two point-of-care lateral flow immunochromatographic tests (Chagas STAT-PAK validated for humans, Chembio Diagnostics; Vida Chagas for dogs, Vida Pharmacal), a multiplex microsphere immunoassay (Luminex), and PCR. Results- Dogs were tested based on clinical index of suspicion (3) or were asymptomatic living in high-risk environments (15). Test results were positive for IFA in 83% (15/18), ELISA in 72% (13/18), STAT-PAK in 39% (7/18), Vida in 45% (5/11), Luminex in 22% (4/18), and PCR in 17% (3/18). Luminex results provide a comprehensive assessment of responses to ~20 selected recombinant proteins identified as major targets of antibody responses in multiple species compared to a control, and positive results correlated with clinical disease. Additionally, the four Luminex positive dogs were the four with IFA titer >1280 and ELISA >3.0. Low positive IFA, ELISA and STAT-PAK results were associated with low reactivity to T. cruzi antigens that remained below the Luminex control. Conclusions and clinical importance- Confirmation of single test results is recommended for low positive results and in asymptomatic dogs. Luminex results may help discriminate active T. cruzi infections in dogs.
