Turnaround: 3-5 business daysTurnaround: 7-10 business days
Price: $45.00Price: £40.00
Breeds: Appaloosa/Friesian, Arabian/Friesian Cross, Baroque Pinto, Friesian, Friesian Cross, Moriesian, Warlander
Description
Distichiasis is an autosomal recessive ocular disorder in which aberrant eyelashes grow from the openings of the Meibomian glands along the eyelid margin and rub against the cornea and conjunctiva. The constant contact of these hairs with the eye can cause irritation, excessive tearing, squinting, redness, inflammation, and discomfort. If left untreated, severe or prolonged irritation may result in chronic keratitis, corneal ulceration, scarring, and impaired vision, and secondary infection can lead to loss of the eye.
The condition is associated with a 16 kb deletion on chromosome ECA13, between the genes FAM20C and PDGFA, identified through whole genome sequencing of affected Friesian horses. Friesians account for the vast majority of reported cases. Inheritance is autosomal recessive with incomplete penetrance, meaning a horse must inherit two copies of the variant to be at risk, and some horses carrying two copies show no signs of the disorder. Distichiasis is not contagious and cannot be transmitted between horses.
Because carriers show no signs, DNA testing of breeding stock is the only reliable way to identify them and avoid carrier-to-carrier matings (N/Dis x N/Dis), which carry a 25% risk of producing an affected foal. Treatment of affected horses depends on severity and may include removal of the abnormal eyelashes, cryotherapy, electrolysis, or other procedures designed to prevent regrowth. Early diagnosis and treatment are important to reduce discomfort and prevent permanent damage to the cornea.
Possible results
| Genotype | Description |
|---|---|
| Dis/Dis | Affected: Horse has two copies of the distichiasis variant and may develop signs of the condition. It will pass one copy of the variant to every offspring. |
| N/Dis | Carrier: Horse has one copy of the distichiasis variant and is not expected to show signs of the condition. Each offspring has a 50% chance of inheriting the variant. |
| N/N | Clear: Horse does not carry the distichiasis variant and cannot pass it on to offspring. |
Breeds Affected
Friesian, Appaloosa/Friesian, Arabian/Friesian Cross, Warlander, Baroque Pinto, Friesian Cross, Moriesian
Reference
[PMID: 33256610]