Occurrence, perception and prevention of ovine fasciolosis in the thirteenth and fourteenth centuries.

Fasciolosis, or liver fluke disease, is a parasitic ailment in sheep that has been responsible for significant mortality in flocks, likely since the Neolithic period. However, the earliest unequivocal description of this condition is medieval, with fasciolosis identified in three French-language agricultural treatises from the 13th and 14th centuries: the anonymous Seneschaucie (England, c. 1270); the Hosebonderie by Walter of Henley (England, c. 1280); and Le bon bergier by Jean de Brie (Ile-de-France, 1379). While the "disease of the dauves" described by Jean de Brie has been previously discussed, fasciolosis does not seem to have been recognized in the two Anglo-Norman works, perhaps because it is not explicitly named. Nevertheless, their etiological and clinical descriptions of the disease, remarkably clear, leave no doubt about the pathology involved. These three texts collectively provide remarkable evidence of the observational and interpretative skills of medieval authors regarding a complex pathological phenomenon, involving not only their domestic livestock but also a parasitic worm whose life cycle would only be elucidated in the late 19th century. The conditions for the onset of the disease are correctly identified, and the diagnostic criteria proposed, both clinical and necropsy-based, are still employed to some extent today. The Seneschaucie goes so far as to propose a comprehensive management plan for the disease, with a collective approach involving semi-random diagnostic slaughters every three years, allowing the detection of the pathogen in the population even before the onset of initial symptoms. In this article, we explore, through a new French translation of the Anglo-Norman passages, the scientific approach adopted by these medieval authors and compare their recommendations with current knowledge on liver fluke disease. Additionally, we present results from other analytical approaches focusing on fasciolosis from the 13th to 14th centuries: the analysis of manorial accounts and of archaeological data. Thus, this manuscript aims, through the example of the liver fluke, to highlight how rigorous empirical observation of an animal disease, considering anatomical, pathological, and zoological criteria, helped mitigate its deleterious effects on medieval livestock economy.