Evaluation of Dogs with Border Collie Collapse, Including Response to Two Standardized Strenuous Exercise Protocols

Abstract

Clinical and metabolic variables were evaluated in 13 dogs with border collie collapse (BCC) before, during, and following completion of standardized strenuous exercise protocols. Six dogs participated in a ball-retrieving protocol, and seven dogs participated in a sheep-herding protocol. Findings were compared with 16 normal border collies participating in the same exercise protocols (11 retrieving, five herding). Twelve dogs with BCC developed abnormal mentation and/or an abnormal gait during evaluation. All dogs had post-exercise elevations in rectal temperature, pulse rate, arterial blood pH, PaO2, and lactate, and decreased PaCO2 and bicarbonate, as expected with strenuous exercise, but there were no significant differences between BCC dogs and normal dogs. Electrocardiography demonstrated sinus tachycardia in all dogs following exercise. Needle electromyography was normal, and evaluation of muscle biopsy cryosections using a standard panel of histochemical stains and reactions did not reveal a reason for collapse in 10 dogs with BCC in which these tests were performed. Genetic testing excluded the dynamin-1 related exercise-induced collapse mutation and the V547A malignant hyperthermia mutation as the cause of BCC. Common reasons for exercise intolerance were eliminated. Although a genetic basis is suspected, the cause of collapse in BCC was not determined.

Pathophysiology of heatstroke in dogs – revisited

“…39,42 EIC was reported in Border collie working dogs, and in racing greyhounds. 43,44 Notably, although a genetic basis in the Border collie is suspected, all 13 Border collies with clinical presentation of EIC were negative for the known DNM1 mutation, as well as for the malignant hyperthermia gene mutation, suggesting an additional mutation. 41 Another reported syndrome in dogs, potentially predisposing them to heatstroke, is exercise induced malignant hyperthermia in English Springer spaniels, in which moderate exercise results in collapse, dyspnea, hyperthermia and hyperlactatemia.…”

Heritability and Genomic Architecture of Episodic Exercise-Induced Collapse in Border Collies

“…Owners were also requested to upload a video of the dog during work for evaluation by an observer trained in the diagnosis of BCC. Criteria for inclusion for BCC cases were developed from our previous studies [4,5] and include: dogs with a history of at least two episodes of typical BCC collapse and video evidence that well-illustrated a collapse episode; age of the first episode was <5 years of age; all episodes occurred during or immediately after strenuous activity; episodes were more likely to occur with excitement and heat; episodes were sudden onset; mentation was altered, with a loss of focus and sometimes a loss of balance; all four legs were affected (rear may be more severe); affected legs were stiff, with increased extensor tone, delayed limb protraction and toe scuffing during walking; no systemic or autonomic signs; episodes usually last 5-15 min; normal between episodes; and episodes were intermittent. Dogs were excluded from the study if their age of onset was greater than 5 years, the episodes were not always exercise-induced, the episodes were very brief (1-2 min), systemic or autonomic signs were evident, if the episodes were determined to be seizures, or if the dog exhibited clinical signs of pain during an episode.…”

“…Gait and mentation both return to normal within 30 min of rest. Excessive panting and severe hyperthermia during episodes may be erroneously reported as heat stroke or heat intolerance, but affected dogs have no clinical or laboratory abnormalities consistent with such a diagnosis, and normal dogs participating in the sustained strenuous activity are comparably hyperthermic [ 5 , 6 , 7 ]. Episodic collapse, identical or highly similar to BCC, also exists in related breeds, including Australian shepherds, kelpies, bearded collies, Shetland sheepdogs, and whippets [ 8 ].…”

“…Most of our medical, epidemiological, and physiological understanding of BCC comes from studies conducted by Dr Sue Taylor and colleagues, who performed pre- and post-exercise evaluations of normal and affected border collies via standardized sheepherding and ball-chasing protocols [ 5 ]. Their work demonstrated that dogs with BCC have normal-appearing muscle biopsies, normal blood glucose, blood lactate, and serum electrolytes, and serum creatine kinase levels [ 5 ]. Collapsing border collies from the sheepherding and ball-chasing cohorts had similar clinical signs and laboratory findings, suggesting the same underlying basis for a collapse in both populations.…”

“…Further, the “extreme hyperthermia” identified after exercise in dogs with BCC was also seen in normal exercise tolerant dogs performing the same exercise [ 7 ]. Lastly, the DNM1 gene mutation responsible for a phenotypically dissimilar form of an exercise-induced collapse in Labrador retrievers and related breeds [ 9 , 10 ] was not identified in a large population of border collies meeting the diagnostic criteria for BCC [ 5 ].…”