Pyrrolizidine alkaloid intoxication outbreaks in fattening pigs associated with drought-related feed contamination

Pyrrolizidine alkaloid (PA) intoxication is a well-documented condition in livestock, resulting from the ingestion of forage and grain contaminated with PA-producing plants. These phytotoxins primarily affect the liver and can lead to severe clinical and pathological disorders, particularly in highly susceptibility species such as pigs. Although sporadic cases of chronic PA toxicosis have been reported in swine, extensive outbreaks affecting large geographic areas have not been previously documented. This report describes a large-scale PA intoxication event affecting multiple intensive fattening pig farms in central Spain. Between September and December 2023, 21 pig production companies, representing more than 200,000 fattening pigs in Castilla y León and Castilla-La Mancha autonomous communities (central Spain), reported up to 80% of animals showing prostration, apathy and, occasionally, dark-coloured urine. Mortality during this period ranged 20-40% of affected pigs. At necropsy, animals exhibited variable discoloration of the livers and bleeding gastroesophageal ulcers. Microscopically, hepatic lobes showed an intense interstitial fibrosis and hepatocyte changes including megalocytosis, karyomegaly and canalicular cholestasis. These findings were compatible with chronic toxic hepatopathy. Toxicological analyses ruled out mycotoxins, heavy metals, and pesticides. However, PA contamination was confirmed in a high proportion of compound feed samples associated with contaminated barley with Europine-N-oxide, Heliotrine-N-oxide, and Lasiocarpine-N-oxide. Preventive measures such as changing the source of cereals, reformulating the feed, and using a toxin binder and detoxifying additives allowed resolution of the outbreak. This report documents a large-scale outbreak of PA intoxication in swine, associated with the use of barley contaminated with PA-producing plants, most likely Heliotropium europaeum, in central Spain. Environmental factors, such as drought followed by humid conditions and reduced herbicide application, likely facilitated PA-containing weed growth and subsequent contamination of cereal crops. This case underscores the growing risk of toxicoses linked to climatic and agronomic factors, emphasizing the need for enhanced monitoring and control of feed sources. The online version contains supplementary material available at 10.1186/s40813-025-00457-2.