Multivesicular cysts in cattle: characterisation of unusual hydatid cyst morphology caused by Echinococcus granulosus

Echinococcus granulosus, the causative agent of cystic echinococcosis, not only often causes unilocular cysts in intermediate hosts, but also in rare cases induces formation of multivesicular cysts which have similar morphology to alveolar cysts. The aim of the present study was to characterise multivesicular and unilocular hydatid cysts in cattle using morphologic and molecular diagnostic tools. Multivesicular cysts were detected in 4 out of 1255 slaughtered cows. Four unilocular cysts were also included in the study to compare with multivesicular cyst morphology. For histopathological evaluation, tissues were fixed in 10% neutral formalin. Following a routine histological tissue-processing procedure, samples were embedded in paraffin blocks and serial sections were cut at a thickness of 4-5 microm. For polymerase chain reaction (PCR), cyst walls and/or protoscolices recovered from six materials were preserved in 70% alcohol. Histopathologically, severity of calcification, fibrous capsule formation and giant cell layer were similar for multivesicular and unilocular cysts. However, the severity of subcapsular inflammation, inflammatory cell infiltration into adjacent organ parenchyma and eosinophil leucocyte infiltration into the cyst lumen was higher in multivesicular cysts. PCR analyses revealed that all unilocular hydatid cysts as well as two out of four multivesicular cysts were G1 genotype of E. granulosus. Molecular diagnosis of the other two multivesicular structures remained inconclusive as DNAs obtained from paraffin-embedded cyst walls were fragmented to small parts, as short as 100 bp, which were not suitable for PCR analyses. In conclusion, molecular analysis concomitant to histopathological examinations is useful in differential diagnosis of multivesicular echinococcosis.