An Electron Microscopic Observation of Viral Particles in the Infected Fresh Water Fish from the Disease Outbreak.

Abstract

Eighteen fresh water fish affected with ulcerative skin disease outbreak in years 1983-1984 from the fish farms and natural canals in Supanburi and Nakhon Pathom provinces were examined for virus particle by using transmission electron microscope. There was no virus particle observed in the ulcerative tissue from eight fish collected, a few different types of virus particles, however, were found in the live cells and one type in the splenic cells. These viral particles may be grouped into two groups according to their different sizes. The first group was a large spherical particles of 45-90 nm. having capsid surrounding the nucleic acid core. The other group was a small virus particles of 10-30 nm. with nonenveloped spherical or icosahedral shaped particles and were crystallized arrays of irregular arrays in cytoplasm or cytoplasmic membrane-bound inclusion body. The groups of virus particles were revealed much morphological similar to Reoviruses in the former and Picornaviruses in the later which are both RNA viruses. This study could not concluded that the virus particles observed were the causative agent of the ulcerative skin disease outbreak of fresh water fish. Further study on their significance in such disease outbreak in being conducted.