Infectivity of internal tissues of Atlantic salmon, Salmo salar L., experimentally infected with the aetiological agent of infectious salmon anaemia (ISA)

• Published in: Journal of Fish Diseases
• Main Authors: DANNEVIG, B. H., FALK, K., SKJERVE, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1994
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1365-2761.1994.tb00259.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2761.1994.tb00259.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2761.1994.tb00259.x

Abstract. Infectivity of internal organs and cells of Atlantic salmon, Salmo salar L., was studied at various times after infection with the aetiological agent of infectious salmon anaemia (ISA). Experimentally infected salmon smolts developed anaemia just prior to the onset of ISA‐mortality. ISA‐infectivity of preparations made from liver, kidney, spleen, plasma, red blood cells (RBC) and head kidney leucocytes was determined by inoculating Atlantic salmon parr with the respective preparations. ISA‐mortality was observed after inoculation of salmon parr with preparations of kidney and liver, and to a minor degree, with spleen and a fraction of head kidney leucocytes (WBC1) collected 7 days post‐infection. At 11 days post‐infection, the infectivity of these preparations increased and ISA‐infectivity was also observed with a second fraction of head kidney leucocytes (WBC2), red blood cells (RBC) and blood plasma. At this time, the ISA‐infectivity of kidney was not significantly higher ( P > 0.05) than that of liver but was significantly higher than all other preparations as judged by Cox‐regression analysis. At days 14 and 18 post‐infection, the infectivity of kidney was significantly higher ( P < 0.05) than that of liver, but not at 21 and 25 days post‐infection. Generally, the ISA‐infectivity of kidney was higher than spleen, head kidney leucocytes (WBC1 and WBC2), RBC and plasma, although the difference was not significant at all time points. For example, at day 25 post‐infection, the infectivity of kidney was only significantly higher than that of spleen and plasma. On a per gram basis, head kidney leucocytes proved to contain higher amounts of infectious matter than RBC. ISA‐infective leucocytes present in the kidney tissue may have contributed to a major part of the infectivity recognized in the kidney preparations. Thus, head kidney leucocytes and other kidney leucocytes also may be considered to be among the most important target cells of the aetiological agent of ISA.