Understanding the genetics causing ocular squamous cell carcinoma in horses

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"Help us find out what genes cause ocular squamous cell carcinoma in horses!"
Animal: Horses & Ponies
Keywords: ocular squamous cell carcinoma, SCC, horse, equine, eye, ophthalmology, genetics, gene
Type: Genetic Study
200 Participants
Background and purpose
Squamous cell carcinoma (SCC) is one of the most common forms of cancer to affect the eye in horses, frequently occurring at the limbus, where the clear cornea meets the white of the eye, or on the nictitating membrane, also known as the third eyelid. This type of eye cancer affects some breeds more than others (e.g., Haflingers) so the objective of this study is to determine the role genetics plays in ocular squamous cell carcinoma in multiple breeds. This study is designed to determine the incidence of SCC, to determine the modes of inheritance and identify DNA variants that put horses at risk for this cancer.
What happens in this study
  • Discussion of the horse’s medical history, documentation on known pedigree information, examination of the horse’s eyes by a veterinary ophthalmologist, photography of the horse to document coat color and any abnormalities found in the eyes, and collection of hair samples from the horse’s mane.
  • Examination of a horse’s eyes is similar to examination of a person’s eyes, with lights and magnifying lenses shone into the eyes to see if they are normal, or if any signs suspicious for ocular SCC are present.
  • For some horses, a blood sample may be collected from the jugular vein, and hair samples may be collected from the mane. This is similar to pulling the mane for show but only pulling a very small sample of about 50 hairs. This blood and hair would be used to isolate DNA for genetic studies to help understand which genes may be involved in the development of ocular SCC.
  • Follow up phone calls or emails may be necessary if any questions about the horse’s medical history arise after the examination. If any horse objects to having their eyes examined or to having blood taken or mane hair pulled, these procedures would not be performed.
Pet owner responsibilities

Financially, you will be responsible for covering any costs associated with injuries sustained while participating in this trial and any costs associated with follow up of your animal at VMTH for assessment.

Participation requirements

We are looking for horses with confirmed ocular SCC (confirmed by pathology), or horses that have not been diagnosed with ocular SCC that are at least 13 years old. Horses that are suspicious for ocular SCC are invited to participate, but confirmation would be required prior to inclusion in the study.

Any horse with confirmed ocular SCC does not need to be evaluated in person to participate. Participation for horses with confirmed ocular SCC involves providing (1) a copy of a pathology report confirming ocular SCC, (2) the horse’s registered name for pedigree analysis, and (3) a blood or hair sample. Horses that have not had ocular SCC and are at least 13 years old will need to be examined by a boarded veterinary ophthalmologist to confirm that they do not have ocular SCC. This may be done at UC-Davis VMTH or elsewhere.

Benefits and risks of participating
We cannot promise any benefits to your horse or other animals from your taking part in this clinical trial; however, possible benefits include lowering the incidence of this common eye cancer, helping breeders to make informed mating decisions, and better prediction of the risk of developing disease for earlier diagnosis and treatment.
If you are selected to participate in the study, the study will cover the costs associated with eye examination, blood collection, and mane pulling; however, if a presumptive diagnosis of SCC is made for your horse, any further diagnostics or therapy associated with the diagnosis of SCC will be your responsibility.
PDF Docs
Clinical Trial Informational Flyer
Study duration and period
Participation in this clinical trial, which could last between 15 minutes to one hour.
Recruitment period
From Oct. 2, 2017
UC Davis Veterinary Medical Teaching Hospital
1 Garrod Drive
Large Animal Clinic - Ophthalmology
Davis, CA 95616
Dr. Mary Lassaline

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