Abattoir monitoring of liver lesions caused by Ascaris suum larvae: a longitudinal study conducted in northern Italy

Introduction: Data supplied by the abattoir monitoring system offer a useful tool both for tracing the prevalence of Ascaris suum milk spot lesions and for conducting large-scale epidemiological studies. Materials and methods: In this study, livers of 754833 slaughtered pigs from 5835 batches and 399 farms located in northern Italy, were evaluated in one of the largest national abattoirs during a year of survey. From each farm data concerning the breeding region and province, the season of post-mortem inspection, the farm size and the type of farm production were collected and the probability of finding a positive animal, i.e. with at least one milk spot lesion, in relation to these factors was estimated by a generalised linear mixed model (GLMM). Results: 368 out of 399 farms tested positive (92.2%), out of 5835 batches of animals, 4395 (75.3%) had at least one positive pig, and out of 754833 carcasses, 198964 showed milk spots, with an overall prevalence of 26.4%. The breeding province and the season of post-mortem inspection were two significant risk factors: a higher risk of finding animals with milk spots was recorded in some Italian provinces and in spring. Conclusions: This study provides data on the prevalence of milk spots caused by A. suum migrating larvae in an area characterised by a high density of pig farms. Given the high prevalence recorded, it is necessary to promote effective communication between abattoir, veterinarians and farmers monitoring the circulation of A. suum, developing specific control plans and enhancing animal health surveillance.