The Fish Viruses

Abstract

Publisher Summary Fish viruses are essentially like the viruses found among the warm-blooded vertebrates. Their morphological, biochemical, and biological properties seem to fit well in the modern schemes of viral classification. There is one important difference: fish viruses evoke replication through a broad temperature range; this property is not known among viruses from Homoiothermic vertebrates. In this respect the fish viruses, together with amphibian and insect viruses, are probably more representative of animal viruses in general. Homoiothermic vertebrates are after all numerically a small proportion of all the animals. A peculiarity among the viruses producing acute disease among salmonids is that, three different agents attack pancreatic tissue and kidneys. Fish virology is comparatively young, and the tissue tropism may be nothing more than coincidence. On the other hand, fish kidneys have hematopoeitic, excretory, osmoregulatory, and endocrine functions. Perhaps this diversity of function and cell type makes them vulnerable to the viruses. It can be seen that most aspects of fish virus characteristics require attention. The nucleic acids of IPN, Egtved, lymphocystis, and Clem's orphan virus are known by indirect means only. This very fundamental determination has yet to be made directly. Similarly, capsomeres number is a virtually unworked field, although there is some evidence that IPN virus has only 12 capsomeres and negative staining has clearly shown the helical configuration of Egtved virus. One of the principal differences between fish viruses and viruses of other vertebrates is the ability to replicate through a wide range of temperatures. Referring again to all animals, it would seem prudent to examine carefully the temperature extremes at which animal viruses replicate. Temperature relations will undoubtedly prove important in further separating major groups of animal viruses.