Avaliação histológica e imuno-histoquímica da colonização vaginal por Leptospira em vacas com fluido vaginal positivo à PCR*

Abstract

Leptospirosis in cattle is characterized by causing significant economic losses due to reproductive problems as well as drop in production of meat and milk. Subsequent abortion may be caused by the persistence of the agent in the reproductive tract and thus become a possible transmission source. This study aimed to investigate through histological and immunohistochemical evaluation the vaginal colonization of cows with polymerase chain reaction (PCR) detection of leptospiral DNA in vaginal fluid. The experiment was conducted in two stages: the first identified carrier animals from the PCR in vaginal fluid samples, urine and kidney belonging to 147 cows for the slaughterhouse under official inspection in the state of Rio de Janeiro. The second performed histological processing of vaginal fragments of animals with vaginal fluid positive to PCR, using hematoxylin-eosin (HE) and immunohistochemistry (IHC) techniques. Of the 147 vaginal fluid samples analyzed, 28% (41/147) were positive in PCR and formed the working group for histological analysis. It is emphasized that from these samples, 82.92% (34/41) had the presence of leptospiral DNA in urine and/or kidney, while 17.08% (7/41) were negative for PCR of urine and/or kidney. Nor pathological changes consistent with Leptospira infection and neither the bacteria were identified in the vaginal epithelium through HE and immune-histochemical techniques. Thus, although we found molecular evidence for the presence of leptospiral DNA in vaginal fluid of carrier ani-mals, the presence of the agent in the vagina or changes compatible with infection were not verified. We believe that further studies are needed to assess colonization by Leptospira in the genital tract of cows.