Percentage of complement-mediated lysis of trypomastigotes. Percent killing = 100 – [(number of parasites after incubation with guinea pig complement/number of parasites after treatment with heat-inactivated complement) × 100]. Inactivated-complement: test serum (post immune obtained 15 days after the last immunization) and heat-inactivated complement (56°C for 30 min), Pre immune: sample obtained before the immunization and complement, and Post immune: test serum (obtained 15 days after the last immunization) and complement. All dogs were non-infected. The values represent the average of triplicate assays ± S.D (* P < 0.05).