Scientists are trying to determine if there is a relationship between CSNB and the white spotting patterns Photo: Appaloosas/Wikipedia

New research indicates that Appaloosa horses that have spotted coats may also be affected by congenital stationary night blindness (CSNB). This finding may lead to gene therapy that can correct the defect that causes CSNB.

Scientists from the University of Saskatchewan in Canada have found a link between LP, the main gene that causes the distinct spotting in some of these breeds, and the development of CSNB. CSNB is an inherited disorder that is there from birth and does not progress over time. Affected horses suffer from a complete lack of night vision, although their day vision is normal.

The research team, led by Dr Lynne Sandmeyer, conducted a study to investigate a possible relationship between CSNB and the leopard complex of white spotting patterns. It also sought to define the clinical and electroretinographic (ERG) aspects of CSNB in the Appaloosa. The researchers studied LP and three groups of horses based on coat patterns indicative of three different genotypes.

"Horses with homozygous coat patterns are affected by CSNB, while those with heterozygous coat patterns have normal night vision," Dr Sandmeyer said.

Homozygous patterns associated with LP have few or no spots in white areas, while heterozygous patterns have scattered spots in the white areas including leopard and blanket spotting.

The researchers found that the structure of the inner eyes of Appaloosa horses was normal in all respects, but that ERG recordings supported the hypothesis that CSNB was caused by "a defect in neural transmission through the rod pathway involving the inner nuclear layer".

"We may eventually be able to provide those cells with the material that they need to activate the physiological process and allow them to work at night," Dr Sandmeyer said. "That's many years down the road, but someday, we may have the means to help these horses."

The results of the study have been published in Veterinary Ophthalmology.

Dr Rebecca Bellone, a biology professor at the University of Tampa in Florida is conducting further research on the causes of the LP gene mutation. She is also the chief molecular biologist of The Appaloosa Project, an international organization dedicated to researching the pigmentation of the Appaloosa breed.

The Appaloosa breed was developed in the Palouse River region of the US Pacific Northwest by the Nez Perce tribe of Native Americans.

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