Yearlings of Indian major carps resist infection against the epizootic ulcerative syndrome pathogen, Aphanomyces invadans

摘要

One-year-plus age groups (yearlings) of Indian major carps (IMC) were artificially infected with the epizootic ulcerative syndrome (EUS) pathogen, Aphanomyces invadans and detailed sequential inflammatory response against the pathogen was delineated. For comparison, the corresponding age groups of EUS-resistant (common carp, CC) and susceptible (snakehead) fish species were used in the artificial infection experiments. In all the fish species the injected spores were able to germinate, but in susceptible fish species the germinated hyphae were able to proliferate massively and cause extensive necrotic pathology leading to severe gross lesions. On the other hand, in IMC and CC, the germinated hyphae were prevented from significant proliferation and spreading to the neighbouring tissues and the lesion area was healed over the experimental period of 15 days and no gross visible lesion was observed. Higher number of inflammatory cells and more efficient epithelioid cell layer formation are believed to play an important role in the defence mechanism of yearlings of IMC and CC against A. invadans infection.