Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co-dominant genetic condition.
Abstract: Historical, clinical and experimental data were collected from 9 horses homozygous for HYPP (H/H). All showed episodes of respiratory stertor, described as a rattling or honking sound, usually within the first week post partum. Five horses had one or more episodes of dysphagia, in 3 horses this was accompanied by drooling and in 3 by weight loss. In comparison, only one of 35 contemporaneous half siblings (of which approximately half would be expected to be of the H/N genotype and half N/N) was observed to have respiratory stertor prior to weaning and none had problems with dysphagia. One mature homozygous stallion was infertile secondary to urospermia. Six homozygous horses died or were subjected to euthanasia; 4 age less than a year, one age 20 months and one age 5 years. The remaining 3 cases were still alive at the end of the study. A comparison of homozygous and heterozygous horses using standardised potassium chloride challenge testing indicated that during attacks homozygotes showed significantly more frequent signs of drooling, prolapse of the third eyelid, respiratory stridor and weakness than heterozygous horses. Homozygotes also had significantly more total abnormalities (including myotonic discharges, high frequency repetitive discharges, and spontaneous activity) on electromyographic examination than heterozygotes. These data imply that HYPP is inherited as a codominant genetic defect, because the homozygotes showed more severe clinical signs of disease than heterozygotes. Homozygous foals would be expected to be produced in 25% of matings in which both parents are heterozygous. Owners and veterinarians should be aware of the risks of this mating.
Publication Date: 1999-04-23 PubMed ID: 10213428DOI: 10.1111/j.2042-3306.1999.tb03809.xGoogle Scholar: Lookup
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Summary
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The research article shares findings about the occurrence and implications of Hyperkalaemic periodic paralysis (HYPP), a genetic condition in horses, concluding that it has a codominant pattern of inheritance, with homozygous carriers displaying more severe symptoms than heterozygous carriers.
Study Procedure and Findings
- The study analyzed historical, clinical, and experimental data from 9 horses who were homozygous for HYPP.
- It was observed that all of these horses displayed episodes of respiratory stertor, a type of abnormal respiratory sound, usually within their first week after birth.
- Five of these horses also experienced one or more episodes of dysphagia, which is difficulty in swallowing. In 3 of these cases, drooling was observed and in three cases, loss of weight occurred.
- Comparatively, only one of 35 studied half-brothers, who were either heterozygous or normal for HYPP, displayed respiratory stertor before they were weaned. None of them experienced dysphagia.
- One studied mature homozygous stallion was found to be infertile due to urospermia, a condition characterized by the presence of urine in semen.
- Of the homozygous horses studied, six either died or had to be euthanized due to their condition. The ages at which this occurred varied. The remaining three homozygous horses were alive at the end of the study.
Comparison of Homozygous and Heterozygous Horses
- The researchers used standardized potassium chloride challenge tests to compare homozygous and heterozygous horses.
- It was found that during HYPP attacks, homozygous horses exhibited signs of drooling, prolapse of the third eyelid, respiratory stridor, and weakness more frequently than heterozygous horses.
- Homozygous horses also displayed more total abnormalities on electromagnetic examination than heterozygous horses. These abnormalities included myotonic discharges, high-frequency repetitive discharges, and spontaneous activity.
Conclusion and Implications
- The study concludes that HYPP is inherited as a codominant genetic defect. This conclusion is based on the observed fact that homozygous horses showed more severe clinical signs of the disease than heterozygous horses.
- In scenarios where both parents are heterozygous for HYPP, about 25% of their offspring would be expected to be homozygous carriers of the condition.
- The authors emphasize that horse owners and veterinarians should be aware of the risks associated with this mating scenario.
Cite This Article
APA
Naylor JM, Nickel DD, Trimino G, Card C, Lightfoot K, Adams G.
(1999).
Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co-dominant genetic condition.
Equine Vet J, 31(2), 153-159.
https://doi.org/10.1111/j.2042-3306.1999.tb03809.x Publication
Researcher Affiliations
- Department of Veterinary Internal Medicine, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
MeSH Terms
- Animals
- Deglutition Disorders / genetics
- Deglutition Disorders / veterinary
- Electromyography / veterinary
- Female
- Genotype
- Heterozygote
- Homozygote
- Horse Diseases / diagnosis
- Horse Diseases / genetics
- Horse Diseases / physiopathology
- Horses
- Hyperkalemia / diagnosis
- Hyperkalemia / genetics
- Hyperkalemia / veterinary
- Male
- Paralysis / genetics
- Paralysis / veterinary
- Potassium Chloride
- Respiratory Sounds / veterinary
Citations
This article has been cited 1 times.- Brosnahan MM, Brooks SA, Antczak DF. Equine clinical genomics: A clinician's primer.. Equine Vet J 2010 Oct;42(7):658-70.
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