A serological survey was conducted in a collared peccary farm in the Peruvian Amazon to investigate variations in leptospiral seroprevalence over a period of 18 months. The first survey in 2003 revealed a prevalence of 100% of leptospirosis in the captive population (n=27) with a total of 9 different serovars (sv) identified. Leptospira spp. Varillal 010 was detected in 100% of the population reaching titers of 1:1600 and 8 other strains were detected sometimes at high titers. A second survey in 2005, confirmed a prevalence of leptospirosis in 86.4% of the sampled population (n=22) and revealed serological conversion to two new serovars in 40% of the herd. The absence of clinical symptoms and serological conversion to previously detected or to new serovars in more than 90% of the herd confirms the circulation of spirochaetes within the captive herd and the possible role the collared peccary as a potential reservoir of leptospirosis.