Dr. van Haeringen Laboratorium B.V.

P311 Night blindness / Coat colour Appaloosa pattern


The CSNB test is a DNA-based test that provides a method to unequivocally identify Congenital Stationary Night Blindness, or CSNB. As an effect of the disease, affected horses are suffering from night blindness, and may have weak vision during the day. The amount of deteriorated vision may differ largely between horses. In addition to reduced vision, affected horses also show abnormal electroretinogram (ERG).

During the last decades, a large number of scientific publications have described the genetic principles of coat colour and coat variation. Coat colours and coat variations are influenced by many hereditary factors. The DNA-tests are based on physiological effects in the body, in which the production and distribution of pigments result in many coat colour variants. In several cases, the coat colour of an animal may only be decided using DNA-tests.

The Appaloosa spotting pattern, also known as Leopard Complex spotting (LP) includes a highly variable group of white spotting- or depigmentation patterns in horses. Appaloosa horses have three additional identifiable characteristics: mottled skin around the muzzle, anus and genitalia, striped hooves and white sclera round the eyes. The Appaloosa pattern is the result of an incompletely dominant mutation in the TRPM1 gene, also known as the LP gene. The LP gene allows for the expression of the various leopard complex spotting patterns while other genes determine the extent (or amount) of white. The CSNB / Leopard Spotting test (P311) tests for the status of the LP (TRPM1) gene. This gene has two variants (alleles). The allele LP is incomplete-dominant and expression of the Appaloosa pattern is variable, ranging from absent to extremely white patterning. At least one copy of the LP allele allows the expression of the Appaloosa pattern. The amount of white present is not dosage related, horses with two copies of the LP allele can have minimal expression of white patterning. The recessive allele N does not have an effect on the basic colour. The variability in the amount of white on Appaloosa-coloured horses is controlled by other genes, one of which is PATN1. Horses that have one copy of the LP allele, in combination with at least one copy of the PATN1 allele most often have a Leopard or a near Leopard pattern. Horses that have two copies of the LP allele in combination with at least one copy of the PATN1 allele most often have a Few-spot or near Few spot pattern. Horses that have two copies of the LP allele suffer from Congenital Stationary Night Blindness (CSNB), which is the inability to see in low to no-light conditions.

Test specific information

Since 2015, two brands have been developed. CombiGen® is mainly directed at veterinarian applications, whereas CombiBreed® is mainly directed at breeders and/or owners. Detailed information about Coat Colours and Coat Variation is presented at www.combibreed.com.


The disease may show itself on different ages, in which it cannot be estimated when the first symptoms may show themselves. Differences may exist between littermates, and between breeds.

Turnaround time

The Turnaround Time (TAT) depends on various factors, such as the shipment time of your sample to the test location, the test method(s) and whether the tests are performed completely or partially by a Partner Lab or Patent owner.

The TAT of tests performed at our facilities is normally 10 working days after receipt of the sample at the testing laboratory (VHL, VHP or Certagen). For tests performed by a Partner Laboratory (so-called "partner lab test") or patent owner, the TAT is at least 20 working days after receipt of your sample. Because the shipment time to our Partner Labs or patent owner may vary due to factors we cannot influence, the mentioned 20 working days are therefore an estimate.

Sometimes it is necessary to re-run your sample. We call this a retest. In that case, the TAT will of course be extended.

Location of disease or trait

This disease mainly affects vision, and may result in blindness.

Breed dependence

This DNA test is available for the following breeds: Appaloosa, Miniature Horse. Additional information is available in the Frequently Asked Questions (FAQ).

Sample type

For this DNA test we accept the following materials: Blood EDTA, Blood Heparin, Semen, Hair, Tissue. Please contact Dr. Van Haeringen Laboratorium if you wish to submit other material as listed.


An animal can be free and has in that situation two healthy alleles. When used in breeding this animal will not become ill due to the disease. It cannot spread the disease in the population.

An animal can be carrier and has in that situation one healthy and one disease allele. When used in breeding 50 percent of the offspring will receive the disease allele. Carriers will not become ill.

An animal can be affected and has in that situation two disease alleles. When used in breeding all offspring will also receive the disease allele. Affected will become ill.


This genetic factor is inherited in an autosomal, recessive, mode. This means, that the individual can be free of the disease (homozygote normal), affected (homozygous affected) or carrier (heterozygous).

Carriers may spread the mutation in a population without showing symptoms themselves. Because of this, it is extremely important to identify carriers correctly to prevent spreading of a mutation.

Severity of Disease


Code P311

Night blindness / Coat colour Appaloosa pattern

€ 57,48 (Incl. 21% VAT)
€ 47,50 (Excl. VAT)