Dr. Kelly E. Knickelbein has been named as the recipient of the 2020 James M. Wilson Award. Presented to a graduate student or UC Davis veterinary hospital resident, this award recognizes an individual who significantly advances equine health through publication of the year's most outstanding research report. Dr. Knickelbein, a resident with the Ophthalmology Service, was chosen for her publication entitled, “A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for ocular squamous cell carcinoma in Belgian horses,” which was published in the Equine Veterinary Journal (2019, 52(1): 34-40). She completed the work under the mentorship of Drs. Mary Lassaline and Rebecca Bellone.
Squamous cell carcinoma (SCC) is the most common cancer to occur on or around the eyes of horses. It often appears as a pink or white tumor, and can grow to affect deeper tissues, leading to loss of the eye, or euthanasia in severe cases. Some breeds, including Belgian horses, are more commonly diagnosed with ocular SCC than other breeds.
This study sought to determine if a previously identified genetic variant in the DNA binding protein 2 (DDB2) gene that is associated with ocular SCC in the Haflinger breed is also associated with the disease in the closely related Belgian breed. The study included 25 Belgian horses confirmed to have ocular SCC (cases) and 18 Belgian horses free of ocular SCC (controls). The data revealed that 76% of the cases had 2 copies of the DDB2 variant, whereas none of the controls had 2 copies of the variant. This indicates that Belgian horses with 2 copies of the DDB2 variant are at 4 times greater risk of developing ocular SCC than horses with 1 or no copies. Since not every case in the dataset had 2 copies of the DDB2 variant, it is suspected that additional genetic factors or environmental influences may explain some cases of ocular SCC in Belgian horses.
A genetic risk test for ocular SCC is now available through the UC Davis Veterinary Genetics Laboratory to identify Haflingers and Belgian horses at increased risk of developing the disease. This will allow owners of high-risk horses to implement best management practices to decrease cancer risk, and enable early detection and treatment. Belgian and Haflinger horses used for breeding can be tested to inform decisions on mate selection in order to limit the production of high-risk horses.