A hard catch: Isolation of local pathogenic Leptospira from Austrian cattle
Creators: name: Sohm, Cynthia
name: Willixhofer, Denise
name: Fasching, Eva
name: Waldner, Karoline
name: Deitzer, Nicole
name: Steiner, Janina
name: Jöbstl, Julia
name: Schleicher, Corina
name: Schwarz, Marcel
name: Fuchs, Reinhard
name: Bourhy, Pascale
name: Kaesbohrer, Annemarie
name: Wittek, Thomas
name: Firth, Clair
name: Steinparzer, Romana
name: Desvars-Larrive, Amélie
Publisher: name: Zenodo
Year: 2024

description: ObjectivesLeptospirosis is a neglected, globally spread zoonotic disease caused by pathogenic bacteria of the genus Leptospira. In cattle, abortion and fertility disorders are commonly associated with leptospirosis and the disease can induce significant economic losses at farm level. People working in close contact with livestock, are at higher risk of infection. Diagnosis of infection by Leptospira spp. is usually conducted via a serological test, the gold standard being the microscopic agglutination test (MAT). For this test a panel of live Leptospira strains, representing the main serogroups, are used. Both the World Organisation for Animal Health and the World Health Organization recommend the inclusion of locally circulating Leptospira strains in the panel to improve the test performance. However, no isolates from Austria have been available for inclusion in the MAT panel, used for the serological diagnosis of leptospirosis in both humans and animals, and the test has relied on non-native isolates.The goal of this study was to isolate and genotype circulating Leptospira strains from cattle in Austria, to enhance the performances of the serological diagnostic for humans and animals. The findings of this study will also further our understanding of the local epidemiology of this zoonotic disease.Material and methodsTo maximise our chances of isolating Leptospira spp., we adopted a targeted sampling approach, focusing on animals considered at higher risk of carrying the bacteria, i.e. i) animals presenting with clinical signs compatible with leptospirosis and ii) animals originating from farms that were considered at high risk of leptospirosis. The inclusion criteria (i.e. individual and farm characteristics) were established based on a systematic literature review on bovine leptospirosis in Europe and a retrospective analysis of national bovine leptospirosis serological data. Additionally, the sampling strategy was complemented by a semi-targeted sampling approach.Between November 2021 and September 2022, we collected urine samples from symptomatic cattle on farms as well as kidney tissue and, if logistically possible, urine samples, from slaughtered animals. All samples were inoculated into culture media and observed for leptospiral growth for at least 12 weeks. The samples were tested by PCR targeting the lipL32 gene for the presence of pathogenic Leptospira. Cultures from PCR-positive samples were prioritised and monitored for up to 30 weeks before being discarded. The isolates where further genotyped by core genome multilocus sequence typing (cgMLST). Moreover, sequencing of the lfb1 gene from PCR-positive samples was performed to determine Leptospira species.ResultsThe systematic literature review and the statistical analysis identified symptomatic cattle as animals with a recent abortion, fertility disorders, icterus, photosensitisation, haematuria, and/or a decrease in milk production. We included an animal if at least one symptom was present. Similarly, identified criteria for defining high-risk farms included: cattle replacements off-farm, access to pasture, large herd size, and history of abortions. We included animals from a farm when at least two of these criteria were present. Overall, we obtained 429 samples from 410 cattle. Six urine and three kidney samples tested positive for pathogenic Leptospira spp. via lipL32 PCR. Sequencing of the lfb1 gene was successful in five urine samples and all of them were identified as Leptospira borgpetersenii.We obtained three Leptospira isolates from the three PCR-positive kidney samples, representing a success rate of 33% in isolating Leptospira from PCR-positive samples. The leptospires exhibited slow growth, showing positive culture after 7-23 weeks. All isolates were identified as Leptospira borgpetersenii serogroup Sejroe serovar Hardjobovis belonging to the cgMLST cluster 40.ConclusionsThis study describes the first isolation and subsequent genotyping of zoonotic bacteria of the genus Leptospira in Austria. By isolating an autochthonous strain and making it available for the MAT panel, this study marks the initial step towards enhancing the performances of the serological diagnostics for both humans and animals within the country. Leptospirosis is commonly considered as a minor disease in both human and cattle Austria. Therefore, the isolation of L. borgpetersenii serovar Hardjobovis from cattle is a major finding, revealing that cattle may act as carriers of Leptospira in Austria and serve as a possible source of infection for humans, other animals, and the environment. Findings of this research suggest that, in case of abortion events in Austrian cattle, leptospirosis should be considered as a differential diagnosis.