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A field investigation into a suspected outbreak of pyrrolizidine alkaloid toxicosis in horses in western Queensland

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Robinson, B. and Gummow, B. (2015) A field investigation into a suspected outbreak of pyrrolizidine alkaloid toxicosis in horses in western Queensland. Preventive Veterinary Medicine, 118 (4). p. 378. ISSN 01675877

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Article Link: http://dx.doi.org/10.1016/j.prevetmed.2014.12.019

Publisher URL: http://www.sciencedirect.com/science/article/pii/S0167587714004462


A disease outbreak investigation was conducted in western Queensland to investigate a rare suspected outbreak of pyrrolizidine alkaloid (PA) toxicosis in horses. Thirty five of 132 horses depastured on five properties on the Mitchell grass plains of western Queensland died in the first six months of 2010. Clinical–pathological findings were consistent with PA toxicosis. A local variety of Crotalaria medicaginea was the only hepatotoxic plant found growing on affected properties. Pathology reports and departure and arrival dates of two brood mares provided evidence of a pre wet season exposure period. All five affected properties experienced a very dry spring and early summer preceded by a large summer wet season. The outbreak was characterised as a point epidemic with a sudden peak of deaths in March followed by mortalities steadily declining until the end of June. The estimated morbidity (serum IGG > 50 IU/L) rate was 76%. Average crude mortality was 27% but higher in young horses (67%) and brood mares (44%). Logistic regression analysis showed that young horses and brood mares and those grazing denuded pastures in December were most strongly associated with dying whereas those fed hay and/or grain based supplements were less likely to die. This is the first detailed study of an outbreak of PA toxicosis in central western Queensland and the first to provide evidence that environmental determinants were associated with mortality, that the critical exposure period was towards the end of the dry season, that supplementary feeding is protective and that denuded pastures and the horses physiological protein requirement are risk factors.

Item Type:Article
Business groups:Animal Science
Keywords:Crotalaria Disease outbreak Horse Pyrrolizidine alkaloid Australia Field investigation
Subjects:Animal culture > Horses
Veterinary medicine > Diseases of special classes of animals > Horses
Live Archive:24 Mar 2015 06:43
Last Modified:03 Sep 2021 16:50

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