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316 Exercise-Induced Collapse in Labrador Retrievers

Exercise-Induced Collapse in Labrador Retrievers Client Education
Sheet
VetBooks.ir Possible Complications

(during exercise, excitement, and increased body
BASIC INFORMATION
temperature). Rarely, affected dogs die during collapse. Cause
Definition of death is unknown; hyperthermia, respiratory
Exercise-induced collapse (EIC) of Labrador DIAGNOSIS muscle weakness, or DMN1 effects on the brain
retriever dogs is a common, breed-associated, are possible mechanisms. No causative lesion
inherited neurologic disorder causing weakness Diagnostic Overview has been found at necropsy.
and inability to stand and walk during or after Diagnosis is suspected based on breed predis-
strenuous physical activity. position and typical episodes of collapse in an PROGNOSIS & OUTCOME
otherwise normal dog. Confirmation is obtained
Epidemiology with a DNA test. Excellent prognosis for a normal life if participa-
SPECIES, AGE, SEX tion in trigger activities can be limited
Dogs of either sex. Signs typically first occur Differential Diagnosis
at 9-18 months of age. • Cardiac arrhythmias, hypoglycemia, gluco- PEARLS & CONSIDERATIONS
corticoid deficiency, and epilepsy can cause
GENETICS, BREED PREDISPOSITION nonpainful episodes of collapse in otherwise Comments
Autosomal-recessive inheritance of dynamin 1 healthy dogs. • EIC is the diagnosis until proven otherwise
gene (DNM1) mutation • Dogs with collapse due to heat stroke are for a healthy Labrador retriever with an
• Only dogs homozygous for the DNM1 mentally abnormal and do not experience episode of pelvic limb collapse during exercise
mutation are susceptible to collapse. rapid spontaneous recovery. that recovers completely by the time the dog
• The mutation and associated collapse are • EIC is the most common reason for is examined by a veterinarian.
common in Labrador retrievers (approxi- exercise-induced collapse in otherwise healthy • The tendency of affected dogs to collapse does
mately 7% homozygous/affected, 38% Labrador retrievers. not change over time, and affected dogs do
heterozygous/carriers). • When collapse episodes are not typical for not develop other associated signs as they
• The condition also occurs in Boykin spaniel, EIC, partial seizures due to epilepsy may be age.
curly coated retriever, Old English sheepdog, more likely.
Chesapeake Bay retriever; rarely in Bouvier Prevention
des Flandres, German wirehaired pointer, Initial Database • Collapse episodes can be prevented by
Welsh corgi, and cocker spaniel • CBC, biochemistry profile, urinalysis limiting participation in trigger activities
• Thoracic radiographs (high-excitement, strenuous activity).
RISK FACTORS • Neurologic and orthopedic exams (pp. 1136 • EIC status should be determined for all
• Homozygosity for the DNM1 mutation and 1143) Labradors before breeding. The high preva-
• Hot weather, high level of excitement: most lence of the mutation in this breed makes it
likely to trigger collapse Advanced or Confirmatory Testing unreasonable to try to eliminate all affected
DNA test for the DMN1 gene mutation: speci- and carrier dogs from the population, but
Clinical Presentation men can be sterile cheek swab/sterile applicator genetic testing makes it possible to avoid
HISTORY, CHIEF COMPLAINT (purchase kit at pharmacy), whole blood producing affected puppies.
Affected dogs typically are normal except (1-3 mL in lavender-top EDTA tube), dewclaws
for episodes of collapse. After participating from puppies (place in plain glass red-top tube), Technician Tips
in strenuous exercise for 5-15 minutes, dogs or semen (1 straw or 0.5 mL in plain glass Death during EIC collapse is rare and may
develop pelvic limb weakness, ataxia, and red-top tube). University of Minnesota College be due to hyperthermia in affected dogs. In a
inability to support weight. Dogs often continue of Veterinary Medicine Veterinary Diagnostic collapsed dog, ensure that nothing is obstructing
to run while dragging the pelvic limbs. This may Laboratory website: https://www.vdl.umn.edu/ ventilation, to facilitate the main source of heat
progress to include all four limbs. Collapse lasts services-fees/canine-neuromuscular-eic dissipation (panting).
5-30 minutes. Dogs appear clinically normal
after recovery. TREATMENT Client Education
Limit participation in trigger activities by dogs
PHYSICAL EXAM FINDINGS Treatment Overview homozygous for DMN1. Halt activity and cool
During collapse, muscles are flaccid, and the Treatment is nonspecific and supportive when dog if the onset of an abnormal gait is apparent
patellar reflex is absent. Body temperature is an episode occurs. during exercise.
high (average 41.7°C [107.1°F]), but this is
normal for exercising Labradors. No cardiac, Acute General Treatment SUGGESTED READING
respiratory, or mentation abnormalities. After • Stop activity at the first sign of abnormal Furrow E, et al: Relationship between dynamin-1
dogs recover, physical and neurologic examina- gait. mutation status and phenotype in 109 Labrador
tion findings are normal. • Cool collapsed dogs (fan, vaporized water on retrievers with recurrent collapse during exercise. J
body, isopropyl alcohol to footpads, cool water Am Vet Med Assoc 242:786-791, 2013.
Etiology and Pathophysiology enemas if severe hyperthermia) (p. 421).
Affected dogs are homozygous for a muta- • No treatment except avoiding participation in AUTHOR: Susan M. Taylor, DVM, DACVIM
EDITOR: Leah A. Cohn, DVM, PhD, DACVIM
tion in DMN1, a protein in the brain and exciting trigger activities, which consistently
spinal cord that is important for repackaging reduces or eliminates the occurrence of col-
neurotransmitters into synaptic vesicles for lapse in affected dogs.
release during high-level neurologic stimulation

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