Ontario. Suspected hypersensitivity to insect bites in market pigs. During an eight-week period between mid-June and mid-August 1989, a skin rash was ...
CROSS-CANADA DISEASE REPORT RAPPORT DES MALADIES
DIAGNOSTIQUtES AU
CANADA
Ontario Suspected hypersensitivity to insect bites in market pigs During an eight-week period between mid-June and mid-August 1989, a skin rash was observed postslaughter in 1,099 of 1,584 pigs killed at a southwestern Ontario processing plant. Twelve producers from two counties regularly shipped pigs either directly to the plant or through two local assembly yards. Affected pigs were associated with each of the 12 suppliers. The rash was characterized by multiple, circumscribed, erythematous lesions, varying from 0.5 to 1 cm in diameter and widely distributed over the surface of the skin. Histologically, a superficial and deep eosinophilic perivasculitis was observed in skin biopsies from three pigs. The pattern and predominance of eosinophils were consistent with those of a parasitic hypersensitivity. In 1987, Becker and Gross (1) reported that mosquito bites were responsible for allergic dermatitis in a group of gilts recently moved
Diseases in baitfish in Ontario Historically, the commercial baitfish industry in
Ontario has involved the capture-harvest of wild baitfish. Mortalities of harvested baitfish occur during all stages of handling, including harvesting, transport, holding in dealer tanks, and prior to use by the angler. Although trauma during capture and water quality problems, such as high temperature and low dissolved oxygen in holding units, are probably responsible for the majority of losses, several specific diseases have been identified from specimens submitted to the Fish Pathology Laboratory of the Ontario Veterinary College. These include skin necrosis and/or "tail rot" caused by either saprophytic fungi (Saprolegnia spp.), or filamentous bacteria such as Cytophaga columnaris (1), or C. psychrophila. Furunculosis, caused by Aeromonas salmonicida subsp. salmonicida, a serious systemic bacterial disease of salmonids, was identified as the cause of mortality in a mixed group of baitfish (2). Large disfiguring tumor-like masses caused by maturing cysts of the myxosporidian protozoa Henneguya notropis, were identified in Notropis spp. baitfish ("shiners") collected from some watersheds. In common shiners N. cornutus Mitchill, a previous report (1) detailed a serious mixed infection involving skin necrosis due to C. columnaris, parasitic meningitis involving myxosporean spores (Myxobolus sp.), intraaxonal parasitism with structures resembling presporogonic stages of a myxosporidian parasite, and mesenteric coccidiosis. Commercial culture of baitfish, such as the white Can Vet J Volume 31, December 1990
to a farm in Florida. Heavy rains during June and early July in southwestern Ontario may have contributed to a larger than normal hatch of mosquito larvae and increased exposure of the pigs to the insects at the farm, assembly yard, processing plant or in transit. The economic loss from trimming was a major concern for the producers. On a single slaughter day, one producer suffered a trim loss of 127 kg. Hypersensitivity to insect bites should be included as a differential diagnosis of porcine skin conditions, particularly during the summer months.
Reference 1. Becker HN, Gross TL. Porcine allergic dermatitis caused by insect bites. Agri-Practice 1987, Summer: 8-11.
Wayne Cole, Veterinary Laboratory Services, Ontario Ministry ofAgriculture and Food, Ridgetown, Ontario NOP 2C0. sucker Catostomus commersoni, is an emerging industry in Ontario. The advantages of culture versus capture include conservation of native forage fish in natural waters, and an alleviation of market shortages during the periods of peak consumer demand. The white sucker is a popular, hardy baitfish that is best cultured in natural ponds that provide clear water and abundant growing space. Efforts to intensively rear these fish in systems similar to those used for salmonid culture, such as fiberglass tanks supplied by recirculated water, appear to be associated with a range of disease problems common to other commercially reared species. In cultured baitfish submitted for diagnostic purposes, we have identified serious gill disease similar to that described in salmonids in Ontario (3). Various problems of vertebral alignment in sucker fry are sporadically encountered, and may be associated with the experimental use of starter feeds intended for salmonid fry.
References 1. Ferguson HW, Lom J, Smith I. Intra-axonal parasites in the fish Notropis cornutus (Mitchill). Vet Pathol 1985; 22: 194-196. 2. Ostland VE, Hicks BD, Daly JG. Furunculosis in baitfish and its transmission to salmonids. Dis Aquat Org 1987; 2: 163-166. 3. Speare DJ, Ferguson HW. Clinical and pathological features of common gill diseases of cultured salmonids in Ontario. Can Vet J 1989; 30: 882-887.
David J. Speare, Vaughn E. Ostland, Hugh W. Ferguson, Fish Pathology Laboratory, Department of Pathology, Ontario Veterinary College, Guelph, Ontario NIG 2 W]. 845
