Parasitic risks and One Health implications of valorising slaughterhouse animal by-products in raw meat-based diets for pets

The increasing popularity of raw meat-based diets (RMBDs) for companion animals has raised One Health concerns regarding their microbiological and parasitological safety, particularly when raw diets are used at home without following standard safety precautions. These diets may serve as a transmission route for zoonotic parasites, posing risks not only to animal health but also to human health and the environment. This study aimed to assess the parasitic risk of animal by-products (ABP's) from sheep and cattle slaughtered in Sardinia, with a focus on zoonotic parasites of veterinary and public health significance. A total of 672 sheep and 503 cattle were examined in seven slaughterhouses between March 2021 and July 2023. Organs were inspected macroscopically, with representative samples subjected to laboratory parasitological analysis. In sheep, Echinococcus granulosus was detected in 67.7 % of animals, with the liver being significantly more affected than the lungs (54.8 % vs. 49.1 %; P = 0.038). Fertile hydatid cysts were more prevalent in the lungs (9.5 %) than in the liver (5.5 %). Cysticercus tenuicollis and Dicrocoelium dendriticum were observed in 2.4 % and 14.7 % of sheep, respectively. Bronchopulmonary nematodes were detected in 44.8 % of cases, and macroscopic Sarcocystis gigantea cysts were identified in 27.7 % of examined oesophagi. In contrast, cattle showed a significantly lower parasitic burden, with E. granulosus detected in only 2.0 % of animals and fertile cysts being rare. Fasciola hepatica was found in 0.4 % of cattle livers, and no Dicrocoelium or bronchopulmonary nematodes were detected. The results demonstrate a high parasitological load in sheep-derived ABPs, reinforcing the need for strict sanitary controls before their inclusion in RMBDs. Given the zoonotic potential of the detected parasites, particularly in endemic regions, the adoption of targeted decontamination measures is essential. These findings underscore the importance of integrating a One Health approach into raw pet food safety, public health and ABP management strategies.