Contents lists available at ScienceDirect Microbial Pathogenesis journal homepage: www.elsevier.com/locate/micpath Susceptibility among breeds of sheep experimentally infected with Leptospira interrogans Pomona serogroup Diego Figueiredo da Costa a , Maria Luana Cristiny Rodrigues Silva a , Gabriel Martins b,c , Antônio Flávio Medeiros Dantas a , Marcia Almeida de Melo a , Sérgio Santos de Azevedo a , Walter Lilenbaum b,c , Clebert José Alves a,* a Transmissible Diseases Laboratory, Universidade Federal de Campina Grande (UFCG), Av. Universitária, s/n, Santa Cecília, 58700-970, Patos, PB, Brazil b Laboratory of Veterinary Bacteriology, Department of Microbiology and Parasitology, Universidade Federal Fluminense, Prof. Hernani Melo St., 101, São Domingos, 24210-130, Niterói, RJ, Brazil c Laboratory of Pathology, Department of Microbiology and Parasitology, Universidade Federal do Estado do Rio de Janeiro, Frei Caneca, 94, Centro, 20211-010, Rio de Janeiro, RJ, Brazil ARTICLE INFO Keywords: Sheep Leptospirosis Susceptibility Resistance Conjunctival route ABSTRACT Leptospirosis is a disease that negatively affects the productive and reproductive indices of ruminants. Sheep are considered highly resistant to infection, although susceptibility may vary among breeds. Thus, the aim of the present study was to analyze the susceptibility between sheep breeds to the experimental infection by leptospires of the Pomona serogroup. Pomona serogroup, Kennewicki serovar strain (1 × 107 bacteria) was inoculated via the conjunctival route in 12 sheep divided into two groups, one comprising Santa Inês ewes and the other comprising crossbred sheep. In each group, five ewes were challenged with the bacterial strain and one was used as control. All sheep were monitored for 60 days, during which blood samples were collected for serological diagnosis and urine and vaginal fluid samples for molecular and microbiological analyses. Finally, as ewes were submitted to euthanasia and necropsy, some tissues of interest were collected for microbiological, molecular, and histopathological diagnoses. The groups were compared regarding the number of positive reactions ac- cording to diagnostic tests. All sheep in each group presented antibodies to Leptospira in all serological analyses, except animals of the control group. However the Santa Inês sheep presented higher concentration and duration of the titers, and their positive reactions were detected earlier than those in crossbred sheep. The antibody titers in group A (median 200, geometric mean 317.48) were significantly different from the group B (median 800, geometric mean 918.96) at D60 post-infection (P = 0,032). The Santa Inês sheep presented a higher number of positive reactions than did the crossbred sheep in the molecular diagnostic tests. According to the molecular diagnosis, the Santa Inês sheep presented more reactions (urine and vaginal fluid) compared to crossbred ewes, but there was no predominance in the detection of leptospiral DNA when comparing urine and vaginal fluid results, nor even between the number of positive kidneys and uterus. The Santa Inês sheep presented a higher number of positive bacteriological cultures. No sheep in either group presented alterations in anatomopatho- logical and histopathological findings. Pure-bred sheep may be more susceptible than crossbred sheep to in- fection by Leptospira sp. Our findings emphasize the importance of the genital tract as a site of extraurinary infection and indicate the possibility of venereal transmission in the species. 1. Introduction The negative effects of leptospirosis on the productive and re- productive indices of ruminants are well understood, and this disease can lead to abortion, estrus recurrence, birth of weak calves, and de- creased milk production [1]. However, despite the importance of this subject, most studies on sheep only calculate the frequency of seropositive animals, and few seek to understand the status of the carrier, the dynamics of the infection, and the nuances of leptospirosis diagnosis in this species. Leptospirosis transmission in animals has been traditionally asso- ciated with their exposure to urine contaminated with the bacteria [2]. However, the constant detection of leptospiral DNA in semen and va- ginal fluid samples suggest venereal transmission in small ruminants https://doi.org/10.1016/j.micpath.2018.06.017 Received 25 February 2018; Received in revised form 23 May 2018; Accepted 8 June 2018 * Corresponding author. E-mail address: clebertja@uol.com.br (C.J. Alves). Microbial Pathogenesis 122 (2018) 79–83 Available online 08 June 2018 0882-4010/ © 2018 Elsevier Ltd. All rights reserved. T