This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
In today’s Science Page researchers L. V. Alarcón, M. Machuca, F. Evangelista, P. M. Negrelli, P. Cipriotti, M. Mayr, V. Regalado, M. C. Villat, L. Benito, E. Ortega, R. Ravone, M. Dibarbora, S. M. Serena, H. R. Sanguinetti, M. G. Echeverría, C. J. Perfumo, and E. Mateu share their results of their study looking at Aujeszky’s disease in Argentina.
Key points
1- The epidemiological pattern of Aujeszky’s disease in Argentina has shifted from sporadic outbreaks in backyard farms to a persistent endemic pattern within large-scale integrated systems.
2-Viral spread to industrial farms has been primarily driven by breaches in biosecurity, including visitors (temporary external personnel), transport biosecurity, and movements of infected animals during the 9–18-day incubation period, plus the time to the diagnosis window.
Introduction
Aujeszky’s disease (AD) in Argentina has transitioned from sporadic small-scale epidemics to an endemic pattern. While historically associated with backyard holdings (with prevalences around 10-19%), since 2023 the disease has spread to large-scale industrial farms that have acted as “super-spreaders”. AD Immunization was not mandatory, with irregular implementation in a few (2 or 3) farms voluntarily utilizing inactivated vaccines. This study aims to characterize the clinical dynamics, biosecurity breaches, and production impact of recent AD outbreaks in large-scale integrated swine networks.
Methods
A descriptive, multi-case study was conducted across six farrow-to-finish and multi-site operations from 2023 to 2025 using retrospective field investigations. Data collection included clinical monitoring and analysis of production records. Diagnostic confirmation was achieved through an integrative approach combining gE/gB ELISA serology, conventional PCR on central nervous system (CNS) tissue, and histopathological identification of non-suppurative meningoencephalitis. Additionally, outbreak investigations conducted within 30 days of detection aimed to identify biosecurity breaches and transmission drivers, such as animal movements and transport logistics, to explain viral persistence in high-density industrial networks.
Results
Spatial analysis revealed a clustered regional distribution consistent with local transmission networks (Fig. 1). Clinical and epidemiological patterns of AD varied by farm. Farm A experienced an acute outbreak in finishers (130–140 days) with respiratory distress and ~6.6% mortality, followed by neurological signs in 90% of suckling piglets. Farm B showed focal neurological disease in 110-day-old pigs with histopathologically confirmed non-suppurative meningoencephalitis. Farm C presented with respiratory disease in older finishers (150–160 days) and with widespread seropositivity in other age groups, with secondary P. multocida and S. suis infections. Farm D, a large multi-site system, reported acute respiratory disease in finishers (140–145 days), along with widespread seropositivity across different age groups and mortality in nursery and reproductive units, resulting in reproductive losses. Farm E exhibited a progressive clinical evolution from reproductive failure to piglet mortality, followed by involvement at the finishing stage. Farm F reported acute respiratory and neurological signs in finishers (130–150 days) with lesions including pulmonary congestion and edema. In general, macroscopic lesions were frequently confounded by bacterial co-infections, leading to misdiagnoses like mycotoxicosis or influenza. Epidemiological tracing identified the movement of inapparently infected replacement animals in the incubation period (9 to 18 days), shared pig transports, and external personnel entering the farm for repairs as primary drivers of viral spread within an average radius of 35 km of the primary foci. The overall production and economic impact across the systems was devastating. Weekly pre-weaning mortality peaked at 71.7–100%, with 90% litter-level morbidity. Nursery mortality reached 4.2–23.7%, while finishing units showed 60–90% morbidity and 5.9–31.6% mortality. Reproductive farrowing rates dropped to 52.9% with mummified fetuses peaking at 15–26.6%. Total financial impact in large systems reached approximately US$2.5 million, with initial vaccination costs exceeding US$660,000 and ongoing expenses of US$2.07 per pig.
Discussion
While Aujeszky’s disease has historically been associated with backyard production, these outbreaks showed a shift in the epidemiological pattern involving now large-scale integrated systems, where high animal density and inter-farm connectivity are present. In some instances, neurological signs in finishing pigs were noticeable; this uncommon clinical picture is mostly associated with younger animals. The uncommon course of the disease, together with a lack of awareness, delayed the diagnosis of the infection. In any case, the spread to large-scale operations was most likely driven by serious biosecurity breaches.