The Situation of Swine Leptospirosis in Hungary and a Proposal for Establishing Requirements for Declared Herd Freedom from Specific Leptospira Species (Serogroups, Serovars) in Domestic Swine Herds

Background: The objective of our study was to identify supporting and/or opposing arguments regarding whether it is worthwhile to launch—or relaunch—a nationwide program against leptospirosis in Hungarian swine herds, modeled after the successful eradication programs for Aujeszky’s disease and PRRS. It is essential to determine which Leptospira serogroups currently infect Hungarian swine herds and the nationwide distribution of this infection. It is of particular importance to ascertain the prevalence of the swine-adapted (hosted) Leptospira strains (Pomona, Tarassovi, Bratislava)—specifically, in how many herds and across what geographical area they occur, and what percentage of breeding stock is affected—as well as how the infection was introduced to the farm. Furthermore, we sought to identify the available options for eliminating specific Leptospira serovars and achieving disease-free status for individual herds. Materials and methods: We had an analysis of more than 180,000 serum samples across 4 years, including seroprevalence for Pomona, Tarassovi, Bratislava and Icterohaemorrhagiae. Antibodies against incidental serovars (Sejroe, Canicola, Grippotyphosa) occurred rarely. Authors describe their experiences with establishing a new, import-based unit with Bratislava and an eradication method of a large-scale swine herd after Pomona infection. Conclusions: Our aim was to define the current leptospirosis status in domestic herds and provide recommendations. Hungary must decide whether to preserve swine leptospirosis freedom—a status that delivers cost savings by eliminating routine vaccination and treatment costs, provides market value for domestic swine health, and protects against a zoonosis—or leave infection unregulated and manage disease conventionally through vaccines and antibiotics, as practiced elsewhere in the EU.