Experimental streptococcal meningo-encephalitis in cultured fish.

摘要: Abstract In 1984 a disease of fish appeared in Israel which spread rapidly cultured fishponds. The affected tilapia ( Oreochromis aura × nilotica hybrids) and trout Oncorhynchus mykiss ). Common carp Cyprinus carpus ), although reared community with were not susceptible to the disease. Various species ornamental cyprinids cichlids also affected. Morbidity was high mortality ranged between 50% (in trout) 30% tilapia). Clinical pathological findings indicated that suffered from meningitis meningo-encephalitis. Two new streptococcal species, Streptococcus shiloi difficile isolated diseased fish. reproduced experimentally both two species. LD 50s S. strains vitro (two three passages on BHI medium) 10 7 –10 8 cfu. virulence these increased (LD 50 : 2 5 cfu) after vivo (brain brain passage without culture agar plates). Highly virulent did differ low by any identifiable extrachro-mosomal elements.