Bovine Leptospirosis in Caatinga Biome, Brazil: New Insights into Diagnosis and Epidemiology

Abstract

Bovine leptospirosis causes economic losses and raises public health concerns. It is possible that there are peculiarities in the epidemiology of leptospirosis in regions with a semiarid climate, such as the Caatinga biome in Brazil, where the climate is hot and dry, and the etiological agent require alternative routes of transmission. This study aimed to close knowledge gaps to the diagnosis and epidemiology of Leptospira spp. infection in cows from the Caatinga biome, Brazil. Samples of the blood, urinary tract (urine, bladder and kidney) and reproductive tract (vaginal fluid, uterus, uterine tube, ovary and placenta) were collected from 42 slaughtered cows. Diagnostic tests included were the microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira spp. antibodies were found in 27 (64.3%) of the animals analyzed using MAT at a 1:50 dilution (cut-off 50), while 31 (73.8%) animals had at least one organ/fluid where the presence of Leptospira spp. DNA was identified, and 29 animals (69%) were positive at bacteriological culture. The highest sensitivity values for MAT were obtained at the cut-off point of 50. In conclusion, even under hot and dry climate conditions, it is possible that Leptospira spp. can spread through alternative routes such as venereal transmission; moreover, a cut-off of 50 is recommended for the serological diagnosis of cattle from the Caatinga biome.

Bovine Genital Leptospirosis: An Update of This Important Reproductive Disease

“…Sejroe strains are transmitted from cattle to cattle, probably not only by a contaminated environment but also during mating. Sexual transmission in cattle has been widely suggested, occurring in male to female direction and vice versa [13,21,22] since the presence of pathogenic leptospires has been reported both in male and female reproductive tract [17,23,24].…”

“…The embryo infection by leptospires had been already demonstrated by the penetration of zona pellucida in an in vitro study [24] and was later reinforced by the presence of leptospiral DNA in the follicular fluid of naturally infected cows [27]; or (b) the inflammation of the endometrium caused by leptospiral infection [39] impairs the uterine environment and the embryonic development, being related to the Pivotal Period 2. Although the presence of leptospires in the uterus of naturally infected cows has been reported [17,22], the exact effect of the infection on embryo development remains to be elucidated. In the physiology of pregnancy, the integrity of the endometrium and its function are pivotal to the nourishment and attachment of the embryo [40].…”

“…The abortions infected by incidental strains such as Pomona or Icterohaemorrhagiae usually present icteric and leptospires may be demonstrated in the kidneys and liver [46]. In contrast, anicteric fetuses with hemorrhagic or even presenting no visible lesions are often associated with infection Although the presence of leptospires in the uterus of naturally infected cows has been reported [17,22], the exact effect of the infection on embryo development remains to be elucidated. In the physiology of pregnancy, the integrity of the endometrium and its function are pivotal to the nourishment and attachment of the embryo [40].…”

“…Leptospires are fastidious and very nutrient-demanding bacteria; therefore, their culture takes too long and presents low sensitivity [61]. On the other hand, molecular techniques such as PCR and qPCR present high sensitivity and specificity [62], are fast to conduct [63], and can be performed in various types of clinical samples such as urine, cervical-genital mucus, endometrial biopsy, semen, fetal tissues, and placenta [17,22,45]. It is noteworthy that the second step for diagnosis, i.e., the molecular investigation in genital samples, is indispensable for a reliable diagnosis since chronic reproductive disease due to genital leptospiral colonization is very often not detected by serology [13].…”

Epidemiology of Leptospira sp. Infection: Current Status, Insights and Future Prospects

“…Bovine genital leptospirosis (BGL) has been proposed as a dissociated syndrome from renal/systemic disease [ 15 ]. Evidence from studies conducted in semiarid areas in livestock (bovine, sheep, swine and goats) have shown that even in the adverse environmental conditions of a semiarid region, leptospires may survive and propagate by the genital alternative route of transmission [ 16 , 17 , 18 , 19 , 20 ]. These findings are important because in such areas the indirect transmission routes are impaired due to the adverse climate conditions for Leptospira spp.…”