Researchers Pinpoint Link Between Appaloosa Coloring and Night Blindness

Congenital stationary night blindness causes vision deficits in Appaloosas with certain coat patterns.

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Appaloosas with coat patterns indicating they are homozygous for LP, the main gene responsible for Appaloosa spotting, are affected by congenital stationary night blindness (CSNB), according to new research by Lynne Sandmeyer, DVM, DVSc, Dipl. ACVO, associate professor at the Western College of Veterinary Medicine.

CSNB is an inherited disorder that is present from birth and does not progress over time. Affected horses suffer from a complete lack of night vision, yet their day vision is normal. In the late 1970s W.A. Witzel first published his research on the subject, demonstrating that a form of CSNB occurs in the Appaloosa breed. However, no subsequent research had been performed to determine the prevalence of CSNB in the breed or its mode of inheritance.

Seeking to expand the understanding of this disease, Sandmeyer, Carrie Breaux, DVM, MA, Sheila Archer and Bruce Grahn, DVM, Dipl. ABVP, Dipl. ACVO, joined forces in 2005 and 2006 to study CSNB in the Appaloosa. With financial assistance from the Equine Health Research Fund, the Western College of Veterinary Medicine, University of Saskatchewan team was able to conduct a large scale, comprehensive study. They aimed at investigating a possible association between CSNB and the leopard complex of white spotting patterns. They also sought to further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa.

The results of this study have just been published in the November 2007 issue of Veterinary Ophthalmology, the journal of the American College of Veterinary Ophthalmologists. The researchers confirmed a direct relationship between type of coat pattern and the presence of CSNB in the Appaloosa

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