LETTER TO THE EDITOR A Case of Tick Paralysis in a Dog DEAR SIR:
Several authors have indicated that certain species of ticks can cause neurotoxicity in mammals (1, 2, 3). The syndrome is believed to be due to a salivary neurotoxin which interferes with acetylcholine synthesis or liberation at neuromuscular endplates resulting in a rapid onset of ascending lower motor neuron paralysis. A five year old male Border Collie was presented to the Marine Drive Veterinary Hospital on June 1, 1978. The owner noticed an acute onset of hindlimb weakness and suspected that the dog had been hit by a car. The animal was unable to ambulate on presentation. On clinical examination, temperature, pulse and respirations were normal. The animal was bright and alert and very ataxic in the hindlimbs, and was unable to walk more than a few steps followed by collapse in the hindquarters. The vaccination status was not current. "Distemper teeth", slight anisocoria and sluggish direct and indirect pupillary reflexes were present. The forelimbs were normal on appearance and on neurological examination the patellar reflexes were absent in both hindlimbs with a normal toe pinch response. Proprioceptive deficits appeared to be present in both hindlimbs as evidenced by knuckling. The anal sphincter tone was normal and the dog could not perform hopping reflexes with the hindlegs. Radiographic scout films of the spine and skull and rectal examination were normal. Differential diagnoses considered were trauma, poisoning, distemper encephalopathy and tick paralysis. Initial treatment consisted of 3 ml of a mixture of penicillin
and dihydrostreptomycin and 2 ml of flumethasone all administered by the subcutaneous route. The owner was contacted for additional history of the case, and, at this point, reported that the animal had been present one week previously 50 miles northwest of Lillooet, British Columbia in the semi-arid zone of the province. At this point, a search of the dog's skin was rewarded by discovery of a large tick embedded at the base of the left ear. The tick was removed and identified as a female Dermacentor andersoni by Dr. J. R. Allen of the Department of Veterinary Microbiology, Western College of Veterinary Medicine, Saskatoon, Saskatchewan. The dog recovered and was clinically normal twelve hours after removal of the tick. Practitioners are advised to consider tick paralysis as a differential diagnosis when presented with livestock and pets showing acute ascending lower motor neuron deficits with a history of exposure to tick infested geographical areas. A. D. BURT, D.V.M. J. S. GAMMIE, B.Sc., M.Sc., D.V.M. S. E. ELLIS, B.Sc.
Marine Drive Veterinary Hospital 1279 Marine Drive North Vancouver, British Columbia V7P 1 T3 References 1. BLOOD, D. C. and J. A. HENDERSON. Veterinary Medicine, 4th Edition. London: Bailliere Tindall. 1974. 2. DELAHUNTA. A. Veterinary Neuroanatomy and Clinical Neurology. Philadelphia: W.B. Saunders Co.
1977. 3. ETTINGER. s. J. Textbook of Veterinary Internal Medicine, Volume 1. Philadelphia: W.B. Saunders Co. 1975.
CONCOURS "SCHERING" POUR ETUDIANTS EN MEDECINE VETERINAIRE Les prix "Schering" sont offerts aux finissants de chacun des trois colleges veterinaires du Canada. Trois prix de $100 seront disponibles pour chaque college. REGLEMENTS 1. Eligibilite: Le concours ne s'adresse qu'aux finissants d'un college veterinaire du Canada. 2. Les prix seront attribues aux auteurs des meilleurs rapports de cas cliniques (de preference: 300 a 1,000 mots), rediges sous forme convenable pour fin de publication dans la "Revue veterinaire canadienne". Veuillez consulter les "Directives aux auteurs" et les Can. vet. J. 19: 347 (December 1978)
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