fish developed "black smolt" disease, characterized by anorexia, lethargy and black skin. Parasites ... fox pups. Four platinum fox pups from three litters of silver.
CROSS-CANADA DISEASE REPORT RAPPORT DES MALADIES DIAGNOSTIQUEES AU CANADA
Atlantic Canada Dermocystidium-like parasite in farmed Atlantic salmon V isceral and systemic infection with a Dermocystidiumlike organism was diagnosed recently in postseawater entry smolts of Atlantic salmon farmed in the Bay of Fundy. In late summer and early fall, young fish developed "black smolt" disease, characterized by anorexia, lethargy and black skin. Parasites were evident histologically in various tissues, including cardiac muscle, liver, spleen, brain and gills, and were associated with inflammation, including formation of granulomas. Small (3-7 Am diameter) parasites developed in melanin-containing macrophages. Marketweight fish also developed disease that was noticeable in mid winter; grossly visible granulomas developed in kidney and liver. In older fish, granulomas were more advanced and parasites were more mature than in smolts. The economic significance of Dermocysidiun sp. infections to farmed Atlantic salmon in the Bay
of Fundy is being studied. A similar syndrome was described recently by Hedrick et al. (1) in farmed Atlantic salmon in California.
Reference 1. Hedrick RP, Friedman CS, Modin J. Systemic infection in Atlantic salmon Salmo salar with a Dermocystidium-like species. Dis Aquat Org 1989; 7: 171-177.
Rick Cawthorn, Department of Pathology and Microbiology, Atlantic Veterinary College, 550 University Avenue, Charlottetown, Prince Edward Island CIA 4P3; Steve Backman, Moore-Clark, Inc., St. Andrews, New Brunswick EOG 2XO; Dave Groman, Department of Pathology and Microbiology, A VC; John O'Halloran, New Brunswick Department of Fisheries and Aquaculture, St. Stephen, New Brunswick E3L 2X4; Gerry Johnson, Department of Pathology and Microbiology, A VC.
Alberta Thymic hypoplasia in weak platinum fox pups
plays an important role in the immune function by supporting the normal development of the paracortical areas of lymph nodes and periarteriolar areas of the white pulp in the spleen (2), the observations of markedly reduced thymic tissue in affected pups suggested immune deficiency as an underlying cause for their "fading" syndrome (3). The use of the parents of such offspring or their litter mates, for further production of platinum pups is not recommended.
Four platinum fox pups from three litters of silver foxes initially grew at a normal rate, but after 3-4 weeks failed to gain weight, became anorectic, lethargic and eventually died with 1-2 weeks. Some animals developed E. coli septicemia and pneumonia. Affected pups had markedly smaller thymuses weighing only 0.2-0.5 g, compared to a weight of 1.7 g in normal pups of similar age. Microscopic examination revealed marked thymic cortical hypoplasia with lack References of demarcation between cortex and medulla. The ratio 1. Onderka DK. Thymic hypoplasia in weak platinum fox pups. Scientifur 1989; 13: 155-158. of lymphocytes to Hassall's corpuscles was 4.42 comRA, Dalmasso AP, Martinez C. The role of the thymus pared to 11.16 for normal pups, thus confirming 2. inGood development of immunologic capacity in rabbits and mice. lymphoid hypoplasia (1). The problem of weak J Exp Med 1962; 116: 773-798. platinum fox pups has been known for almost fifty 3. Roth JA. Possible association of thymus dysfunction with fading syndrome in puppies and kittens. Vet Clin North Am Small Anim years. It is thought to be a genetic problem, the mechPract 1987; 17: 603-616. anism of which is not fully understood. It does not occur in all platinum offspring, but is sufficiently widespread on some ranches in western Canada to cause Detlef Onderka, Alberta Department of Agriculture, problems in production. In this case, 7 of 15 platinum Animal Health Division, Veterinary Laboratory, pups died despite supportive therapy. Since the thymus 6909 - 116 Street, Edmonton, Alberta T6H 4P2.
Can Vet J Volume 31, August 1990
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