First report of seropositivity to pathogenic Leptospira in backyard hens: potential poultry health issue and zoonotic risk.

Leptospirosis, a bacterial zoonotic disease of worldwide distribution, has not been extensively studied in birds, although leptospiral infection has been described in these animals. In this study, 62 backyard hens were sampled in three suburban areas near the city of Puerto Montt, southern Chile. A panel of eight serogroups and serovars of pathogenic Leptospira were tested using the Microscopic Agglutination Test to determine the seropositivity rate, serogroups, and serovars causing serological reactions, and to quantify antibody titers. A seropositivity rate of 51.61% (32/62) (95% Confidence Interval= 39.17%-64.05%) was estimated, with reactivity detected most frequently for the Sejroe (serovar Hardjo) (34.4%; n = 11), followed by Autumnalis (serovar Autumnalis) (21.9%; n = 7), Pomona (serovar Pomona) (9.4%; n = 3), and Canicola (serovar Canicola) (3.1%; n = 1) serogroups. Of the animals that tested positive, 53.1% reacted to a single serogroup, while 25.0% reacted to four different serogroups; 12.5% reacted to three serogroups, and 9.4% reacted to two serogroups. Coagglutinations were present in 31.3% (n = 10) of the seropositive samples, with Hardjo/Pomona/Tarassovi/Autumnalis (40.0%; n = 4) being the most frequent combination. Antibody titers ranged from 1:100 to 1:3200, with 1:100 being the highest proportion. The high seropositivity rate, presence of anti-Leptospira antibodies, and cross-reactivity among serogroups/serovars in the sampled hens indicate exposure to the bacteria and reveal an unknown potential poultry health issue and a zoonotic risk concern that require awareness given the widespread practice of poultry farming worldwide.