Prevalence of fasciolosis in slaughtered dairy cattle from São Miguel Island, Azores, Portugal.

Fasciolosis, caused by the trematode Fasciola hepatica, is considered one of the most important parasitosis in dairy cattle due to significant economic losses. The main objectives of this study were to determine the prevalence of fasciolosis in dairy cattle slaughtered at São Miguel Island (SMI) slaughterhouse and to ascertain areas (parishes and dairy herds), within the island, with highest risk for fasciolosis. The association among cattle age and weight with the occurrence of fasciolosis was also determined. From a sample of 24,389 cattle slaughtered in two years (2015-2016), a total of 1134 dairy cattle livers were inspected and, during this period, 531 were positive to fasciolosis and 603 presented no typical fasciolosis lesions. This study showed that fasciolosis has a broad geographical distribution on SMI and that is also found in cattle from other islands of the Azores archipelago, namely Flores Island. Although there were no significant differences in weight between healthy animals and parasitized ones, we observed that the older animals present a greater level of liver lesions and a higher level of parasitization, reflecting their longer period of exposure to the risk factor (ingestion of metacercariae in pastures infested by Galba truncatula).