Narcolepsy (canarc1 Labrador)
With narcolepsy (canarc-1) dogs suffer cataplectic episodes, a sudden onset of temporary flaccid paralysis of individual muscle groups or the entire skeletal musculature. Triggers are excitatory events or fright. Affected dogs also show unusual fatigue during the day.
This genetic variant of the disease occurs in the Labrador Retriever. The inheritance is autosomal recessive.
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- Fatigue during the day
- Cataplexy → sudden, temporary flaccid paralysis of individual muscle groups (partial paralysis), or of the entire skeletal musculature (total paralysis).
- Partial paralysis: e.g. weakness of the hind legs leading to sudden sitting down
- Total paralysis: falling down with subsequent inability to move (similar to consciousness)
- The first symptoms occur in the first 6 months of life.
- Triggers are excitatory events (feeding, playing).
- The paralysis lasts from a few seconds to five minutes.
- The episode ends when the dog is touched or spoken to loudly and is completely reversible.
- The severity of the disease is defined by the frequency of cataplectic episodes within a certain period of time.
Genotype and Lab Report
Inheritance: autosomal recessive
→ The disease only occurs if both alleles of the gene are affected by the mutation (narc/narc). Dogs that have only one allele with the causative mutation (N/narc) are clinically healthy carriers.
N/N = genetically normal
The dog has no variants for narcolepsy and therefore cannot pass it on to its offspring.
N/narc = a carrier
The dog is a clinically healthy carrier. The variant is passed on 50% to the offspring, who are also carriers.
narc/narc = affected
The variation is passed on 100% to the offspring. The offspring are carriers or affected.
- Carrier animals can be bred to normal animals (N/narc x N/N). Before using the offspring in breeding, it should be tested whether they are normal or carriers.
- Mating two carrier animals (N/narc x N/narc) should be avoided because there is a 25% chance that the offspring will be affected.
- Affected animals (narc/narc) should be excluded from breeding.
Lin, L., Faraco, J., Li, R., Kadotani, H., Rogers, W., Lin, X.Y., Qiu, X.H., de, Jong, P.J., Nishino, S., Mignot, E.: The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene Cell 98:365-376, 1999. Pubmed reference: 10458611.
Hungs, M., Fan, J., Lin, L., Lin, X.Y., Maki, R.A., Mignot, E.: Identification and functional analysis of mutations in the Hypocretin (Orexin) genes of narcoleptic canines Genome Research 11:531-539, 2001. Pubmed reference: 11282968. DOI: 10.1101/gr.161001.
Further information is available at: Online Mendelian Inheritance in Animals.