Experimental alveolar echinococcosis in pigs, lesion development and serological follow up

Liver lesions were found in 6/6 pigs 7 months after oral inoculation with 5000 or 35,000 Echinococcus multilocularis eggs. However, lesion morphology differed considerably among the animals. The largest lesions (3-8 mm in diameter) were found in a single pig and smaller lesions (1.5-3 mm) in three pigs. These lesions were clearly circumscribed and had pronounced central necroses and dystrophic calcifications. In contrast, most of the smallest (usually <1.5 mm in diameter) found in two other pigs, had small compact fibrotic areas and blurred borders with obvious fibrous infiltrations into the interlobular tissues. E. multilocularis specific DNA was detected by PCR in all lesion types, but metacestode viability, as assessed by in vivo intraperitoneal inoculations in jirds, could not be demonstrated. Within 1 month post inoculation, all pigs developed specific IgG antibody responses against a battery of different antigens (metacestode, cyst fluid, and protoscoleces-derived native E. multilocularis and E. granulosus antigens, affinity purified Em2G11 antigen, antigen B, recombinant Em II/3-10 antigen). Two different reaction patterns were recorded. In the two pigs with the small lesions, pronounced reactions against all crude antigens with peaks 3-5 months p.i. and clearly elevated levels until the end of the experiment were noted. In all other pigs, antibody reactions remained low in all cases. In conclusion, we demonstrated two types of E. multilocularis metacestode development in pigs with distinct immunological response patterns.