Increased Susceptibility of Rainbow Trout to Infectious Hematopoietic Necrosis Virus After Exposure to Copper

Abstract

Exposure of rainbow trout to sublethal levels of copper in water increased their susceptibility to infectious hematopoietic necrosis virus. In most instances, the percent mortality was twice as great in the stressed groups compared with those groups which were not stressed but received the same virus dose. Although the level of copper in the water influenced the mortality rates, the length of exposure did not prove to be critical, as similar results were obtained after 1, 3, 5, 7, or 9 days of exposure. When different virus challenges were employed, the percent mortalities were again greater in the stressed fish at all virus doses tested, and at one dose level mortalities were noted in the stressed group but not in the untreated group.

In vivo effect of zinc and copper on the development of listeriosis in zebrafish, Brachydanio rerio (Hamilton‐Buchanan)

“…The presenee of Cu"^ before and after infeetion increased zebrafish susceptibility to listeriosis. Similar results have been obtained by other authors, who reported that some teleosts demonstrate an increased susceptibility to bacterial diseases (Baker & Knittel 1983) or to viral infeetion (Hetrick, Knittel & Fryer 1979) after copper treatment.…”

Cortisol can increase the susceptibility of brown trout, Salmo trutta L., to disease without reducing the white blood cell count

“…The mechanisms involved in this response to cortisol elevation require further examination. Deleterious changes in the environment are associated with the outbreak of disease (Pippy & Hare, 1969;Giussani et al, 1976;Rodsaether et al, 1977;Brown et al, 1979;Hetrick et al, 1979;Knittel, 1981;Ewing et al, 1982) and both acute and chronic stresses have been shown to depress the number of circulating lymphocytes in teleost fish (McLeay, 1975a;Peters et al, 1980;Tomasso et al, 1983). With acute stresses this effect has been shown to be mediated by elevated cortisol levels (Pickering, 1984).…”

Differences in the sensitivity of brown trout, Salmo trutta L., and rainbow trout, Salmo gairdneri Richardson, to physiological doses of cortisol

“…However, prolonged elevation of blood cortisol levels has been shown to predispose some species of salmonid fish to infectious diseases (Pickering & Duston, 1983;Pickering & Pottinger, 1985;Woo et al, 1987), an effect almost certainly mediated by the suppressive action of corticosteroids on the fish's defence systems (Anderson et al, 1982;MacArthur et al, 1984;Grimm, 1985;Maule et al, 1987). There is now an accumulating body of evidence linking various forms of stress to a subsequent increase in the susceptibility of fish to a wide range of infectious diseases (Johansson & Bergstrom, 1977;Hetrick et al, 1979;Hanson & Grizzle, 1985; see also Wedemeyer & McLeay, 1981) and we believe that elevated cortisol levels play a major role in this phenomenon. In general, rainbow trout are more amenable than brown trout to aquaculture conditions and, in our experience, show fewer problems of stress-related diseases.…”