Genetic testing as a tool for diagnosis of congenital stationary night blindness (CSNB) in white spotted breeds in Poland.
Authors: Stefaniuk-Szmukier M, Bieniek A, Ropka-Molik K, Bellone R R
Journal: Journal of equine veterinary science
Summary
# Congenital Stationary Night Blindness in White-Spotted Horses: Genetic Testing Reveals Breeding Implications Congenital stationary night blindness (CSNB) affects horses carrying the leopard complex spotting phenotype and is caused by a specific 1378 bp insertion in the TRPM1 gene, with homozygous carriers experiencing permanent low-light vision impairment—a significant welfare and safety concern for animals working in dim conditions. Polish researchers genotyped 221 horses across three breeds (Małopolska, Felin ponies, and Shetland ponies) using a three-primer allele-specific PCR system to establish CSNB prevalence in tartan-coloured populations. Between 4.8 and 7 per cent of LP-carrying horses in these breeds were homozygous for the TRPM1 insertion, indicating a measurable population frequency of clinically night-blind individuals. The genetic markers maintain Hardy-Weinberg equilibrium across tested populations, making straightforward genetic screening a viable tool for identifying affected animals and carriers before clinical signs manifest. For equine professionals involved in breeding decisions, performance evaluation, and stable management, this work underscores the practical value of TRPM1 genotyping—particularly for horses expected to work in low-light environments or those with white-spotted coats—enabling informed selection against CSNB homozygosity and reducing the risk of placing visually compromised animals in unsuitable roles.
Read the full abstract on PubMed
Practical Takeaways
- •Use genetic testing for TRPM1 insertion to identify night-blind horses before purchase or breeding, particularly in spotted breeds where clinical signs may be subtle
- •Homozygous carriers of the TRPM1 insertion have significant low-light vision impairment and should be managed carefully or excluded from breeding programs and work requiring dim-light conditions
- •Genetic screening is a practical, non-invasive tool that should be incorporated into breeding strategies and pre-purchase evaluations for white-spotted horses in Poland
Key Findings
- •TRPM1 gene insertion was genotyped in 221 horses from three Polish breeds using allele-specific PCR
- •7% of Małopolska horses, 4.8% of Felin ponies, and 6.25% of Shetland ponies carrying the LP allele were homozygous for the TRPM1 insertion causing night blindness
- •The studied populations were in Hardy-Weinberg equilibrium, indicating stable allele frequencies
- •Genetic testing enables accurate identification of night-blind horses, informing breeding and management decisions for animals working in low-light conditions