Diagnostics and epidemiology of alveolar echinococcosis in slaughtered pigs from large-scale husbandries in Germany.

By means of the official meat inspection of domestic pigs, exceptionally high proportions of livers affected by encapsulated nodules containing whitish to light yellow, viscous to pasty material ("microabscesses") were detected. The swine had been raised on four different farms, being located in distinct regions of Germany (Brandenburg, Thuringia, Upper Franconia). Macroscopical and histological examination of 77 samples of livers revealed granulomatous to necrotizing hepatitis with attendance of numerous eosinophils. In 61 % (n = 47) of the lesions, eosinophilic, band-like acellular structures resembling the laminated layer of Echinococcus sp. were visible. Moreover, representative samples (n = 11) showed a positive reaction of these structures with Periodic acid-Schiff. Altogether, the findings were consistent with alveolar echinococcosis. Echinococcus multilocularis DNA could be demonstrated in selected samples (n = 7) by polymerase chain reaction. Epidemiological considerations suggest contamination of the forage with fox tapeworm eggs to be the most likely source of infection on two of the farms, as some of the fodder had been stored in the open, being amenable to infected definitive hosts. On the two other farms, mainly straw litter has to be taken into account regarding the transmission route, since carnivores excreting eggs of E. multilocularis could have gained access to the straw storage. The presented cases show that adequate mechanisms of meat inspection may provide important data for the purposes of surveillance and risk assessment of human alveolar echinococcosis.