Streptomycin treatment of genital carriers of Leptospira in experimentally infected sheep on different estrous phases.

Leptospirosis in ruminants presents as a chronic disease that causes several reproductive disorders leading to severe economic losses. The current recommended treatment can be efficient to eliminate the renal carrier state, however little is known about the effect of this drug in removing the genital carrier state and the hormonal influence on it. A total of 12 primiparous sheep experimentally infected with a strain of Leptospira santarosai serogroup Sejroe, FV52 strain, were used and distributed as group A (estrus; n = 5), group B (metaestrus; n = 4) and group C (control; n = 3). At D0, groups A and B were treated with streptomycin (25 mg/kg) single dose. Samples of cervicovaginal mucus (CVM) were collected on days 0, 3, and 35 post-treatment, while uterine fragment (UF) samples were collected on days 3 and 35, for PCR. Even after antibiotic treatment, all groups presented infected animals, at D3 and D35, with no significant difference between the treated and control groups. Based on these results, it was conducted a second protocol of treatment with streptomycin, IM (25 mg/kg) for three consecutive days, which was 100% effective to eliminate the genital carrier state; therefore, that protocol should be recommended.

The Efficacy of Vaccination in the Prevention of Renal and Genital Leptospirosis in Experimentally Infected Sheep.

(1) Background: Leptospirosis, mainly determined by strains belonging to serogroup Sejroe, has a direct impact on the reproductive efficiency of ruminants, such as sheep. In Brazil, Leptospira santarosai serovar Guaricura, known to be able to chronically colonize the uterine environment, is of special note. Although vaccination minimizes the effects of acute disease, whether or not it can protect from renal colonization remains controversial, and its effects on the genital tract are unknown. In this context, the present study aims to investigate the efficacy of vaccination in the prevention of experimental genital leptospirosis. (2) Methods: Eighteen sheep were divided into three groups: one vaccinated with a polyvalent commercial bacterin, one vaccinated with an autologous bacterin, and one unvaccinated. After 14 days, the sheep were experimentally challenged with 108 leptospires (L. santarosai, serogroup Sejroe, serovar Guaricura, strain FV52) intraperitoneally. Serology and colonization of the urinary and genital tracts were carried out monthly by PCR for 210 days in all animals. (3) Results: Vaccination significantly elicited antibody titers with a predominance of agglutinins against serogroup Sejroe. Both urinary and genital infections were confirmed by PCR. Positivity in urine PCR was absent after D120, while genital infection persisted until the end of the study. Serological results and the finding that vaccination did not avoid renal colonization align with previous studies. Despite vaccination, Leptospira established chronic and asymptomatic colonization of the genital tract until D210, an outstanding finding that remains to be fully understood in its mechanisms. (4) Conclusions: This is the first study conducted to analyze the effects of vaccination in the prevention of genital leptospirosis.