Postville (February), Nain, Cartwright and Churchill ... south than Cartwright, there have been cases in the ... Department ofForestry and Agriculture, St. John's,.
CROSS-CANADA DISEASE REPORT RAPPORT DES MALADIES DIAGNOSTIQUEES AU CANADA
Labrador Rabies epizootic in Labrador Dabies appears in Labrador on a cyclical basis,
depending upon the spread of the disease within the populations of arctic foxes farther north. The last epizootic occurred in 1988 (1) and, at that time, was the largest wave of cases seen since the late 1940's. This year has seen the arrival of another wave that is even broader in its geographical scope than the one in 1988; it has also extended further into the summer than previously recorded. It is felt that this wave will continue south to affect the more populated areas of Quebec, possibly within the coming year. From January 1 to September 10, 1992, 13 of 25 animals from 11 different communities were positive for rabies. Advance warning for such epizootics in Labrador usually comes from confirmation of rabies in northern Quebec and Baffin Island. In this case, reports from Nain (April, 1991), La Forge 1 (July, 1991), Kuujjuaq (September and December, 1991), Schefferville (January, February and March, 1992) and Iqaluit (February, 1992) helped us to forewarn residents, and to be prepared ourselves. Confirmed cases to date in 1992 in Labrador include Hopedale, Esker and Postville (February), Nain, Cartwright and Churchill Falls (May), Goose Bay and Rigolet (May and June), and Makkovik (September) (Figure 1). All of these outbreaks occurred in either arctic foxes or red foxes. These facts indicate an epizootic of rabies that is spreading across all of Labrador and well into Nouveau Quebec. Although there has not been any confirmation of rabies on the Labrador coast farther south than Cartwright, there have been cases in the Havre St. Pierre/Longue Pointe region of the north shore of the St. Lawrence River. The absence of any recent historical evidence of the disease in the area suggests that this may be a further southern extension of this wave. As elsewhere in Canada, populations of foxes are very high in Labrador this year, because of a peak in the cycle and of minimal trapping pressure as a result of low prices for pelts. Usually, we expect epizootics of rabies to stop by May or June, but unconfirmed cases suggest that the disease has continued well into
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Figure 1. Map showing the location of cases of rabies in Labrador and vicinity from April 1991 to September 1992. the summer. The facts emphasize the need to monitor these geographical and temporal extensions of rabies, as residents often become complacent if they are not continually reminded through publicly announced confirmations that the disease continues to exist in the area. Officials in more southern regions are forewarned that this wave may be heading in their di'rection.
Reference 1. Whitney HG. Rabies outbreak. Can Vet J 1988; 29: 665.
Hugh Whitney, Director, Animal Health Division, Department of Forestry and Agriculture, St. John's, Newfoundland AlE 3 YS
Ontario Menadione (vitamin K3) toxicity in six horses
Canada, Inc., Victoriaville, Quebec) about three hours prior to racing, in order to control exercise-induced Six standardbred horses in training were given pulmonary hemorrhage. The amount of menadione is intravenous injections of approximately 200 mg of uncertain; also mixed in the 60 mL syringe used were menadione sodium bisulfite (50 mg/mL, Vitamin 7%7o N-butyl alcohol (Clotol, rogar/STB Inc., Pointe K3-50, PVU Division of Sanofi Sante Animale, Claire, Quebec), aminocaproic acid (Amicar, Lederle-
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Can Vet J Volume 33, November 1992
Cyanamid Canada Inc., Markham, Ontario), and calcium. Within 4-48 hours of administration of this medication, the horses became depressed, anorectic, weak, had muscle stiffness and colic, and became markedly azotemic (serum urea and creatinine 5-1OX normal). Horse 1 did not improve, and was euthanized on day 10. Horse 2 developed laminitis, was treated with intravenous fluids, developed polyuria that did not resolve, and was euthanized on day 50. Another two horses developed polyuria and severe weight loss, and improved slowly; the other two horses recovered uneventfully. Gross lesions in horse 1 included: marked enlargement of both kidneys (right, 2.75 kg; left, 3.0 kg); pale, mottled renal cortices; cranioventral bronchopneumonia; and gastric ulceration. Histologically, there was marked subacute nephrosis characterized by: marked tubular dilation; attenuation of tubular epithelium; casts consisting of hemoglobin, red cells, and necrotic neutrophils and tubular epithelial cells; marked interstitial edema; and occasional tubules that were partially lined by regenerating epithelium. There was in addition mild generalized alveolitis. Laminitis was confirmed at necropsy of horse 2; there was also renal papillary necrosis and patchy renal cortical pallor that was due to interstitial cortical fibrosis. Menadione (synthetic vitamin K3) is recognized to be nephrotoxic in horses at a dosage of 1000-2500 mg,
and this incident is very similar to those previously reported (1,2), though the dose in our cases was apparently lower. The pathogenesis of the nephrosis is not understood, and may include direct tubular damage and/or "hemoglobinuric nephrosis". The prognosis for horses with vitamin K3-toxicosis is generally poor because interstitial renal fibrosis and renal failure often ensue. Vitamin K3 should be used only in the treatment of vitamin K deficiency, eg. warfarin toxicity, and not for the prevention of epistaxis. The label indications for use of the drug are "to prevent and treat blood coagulation problems (hemorrhagic syndrome)".
References 1. Rebhun WC, Tennant BC, Dill SG, King JM. Vitamin K3-induced renal toxicosis in the horse. J Am Vet Med Assoc 1984; 184: 1237-1239. 2. Green EM, Green SL. Vitamin K3: Toxicosis and therapeutic considerations for use in horses. Mod Vet Pract 1986; 67: 625-628.
Grant Maxie, Tony van Dreumel, Veterinary Laboratory Services Branch, Ontario Ministry of Agriculture and Food, Box 3612, Guelph, Ontario NIH 6R8; Dan McMaster, Vernvale Veterinary Services, R.R. 1, Moffat, Ontario LOP IJO; John Baird, Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Ontario NIG 2W1
Western Canada Western Canada rabies diagnoses January 1-June 30, 1992 reporting period. Most of the positive cases in Manitoba occurred in the southwestern corner of the province which traditionally is the location of most rabies cases in Manitoba. However, a number of positive cases have appeared in the south central area and in southeastern Manitoba, east of the Red River. The Bat cases east of the Red River may be an extension of the Fox Skunk increase in rabies that has been noted in Minnesota. Others A number of rabid skunks were also found in the Total southern interlake area and one rabid cat was found in the city of Winnipeg. As there has been no other From January 1 to June 30, 1992, the rabies unit case of rabies within 30 km of Winnipeg, this case may at the Animal Diseases Research Institute (ADRI), be attributable to bat rabies. Investigations are curLethbridge, received 1388 specimens, of which 110 rently underway to determine the origin of this strain were found to be positive for rabies. Compared to the of virus. same period for the previous year, this represents a In Saskatchewan, there was nearly a 1000/0 increase 6% increase in the number of submissions and a 22% in the number of positive skunks, compared with the increase in the number of positive diagnoses. The most same period in 1991. Most cases diagnosed were from noteworthy observation for this recording period is the the Estevan area, but foci were also found near Swift dramatic increase in the number of rabid skunks in Current, Yorkton, and Regina. Manitoba and Saskatchewan. Since 1989, the number of positive diagnoses made annually in western Canada has been increasing consistently. Ken Loewen, Josephine Kush, Rabies Diagnostic LabDuring the same period in 1991, there were 33 posi- oratory, Animal Diseases Research Institute, Box 640, tive skunks in Manitoba, compared with 50 in this Lethbridge, Alberta TIJ 3Z4 Species Cat Cattle Dog Horse Sheep
BC 0 0 0 0 0 3 0 0 0 3/67
AB
0 1 0 0 0 0 0 2 0 3/551
SK 0 1 0 0 1 1 0 29 0 32/413
MB
1 8 0 1 0 0 0 50 0 60/337
Can Vet J Volume 33, November 1992
YT NWT
0 0 0 0 0 0 0 0 0
0 0 3 0 0 0 9 0 0 12/20
Totals
1/184 10/100 3/247 1/8 1/3 4/147 9/60 81/495 0/144 110/1388
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