What is NCL in American Bulldogs?

Neuronal Ceroid Lipofuscinosis (NCL) is an autosomal recessive neurodegenerative disorder caused by a mutation in the CTSD gene. Affected American Bulldogs typically show neurological symptoms (loss of coordination, behavioral changes, eventual blindness) starting between 18 months and 4 years of age. The condition is fatal.

Can NCL be tested for?

Yes. The Embark genetic panel and several other DNA tests identify the CTSD mutation. Test result categories: clear (no copies of the mutation), carrier (one copy, will not develop disease but can pass to offspring), or affected (two copies, will develop disease).

How do responsible breeders use NCL testing?

Test every breeding dog. Pair carrier-to-clear or clear-to-clear only. Never breed carrier-to-carrier (25% of puppies would be affected). Disclose the test results of both parents to the buyer.

Are Rosebull dogs tested for NCL?

Yes. Every Rosebull breeding dog runs the full Embark genetic panel which includes NCL. Results are linked from each parent dog's profile on rosebull.com and verifiable on Embark.

NCL (Neuronal Ceroid Lipofuscinosis) in American Bulldogs

Neuronal Ceroid Lipofuscinosis (NCL) is one of the most serious genetic conditions in the American Bulldog gene pool. It is fatal, it has been documented in the breed for decades, and it is fully preventable with proper genetic testing of breeding stock. This page exists so American Bulldog buyers know what to ask their breeder.

What NCL is

NCL is an autosomal recessive neurodegenerative disorder. In American Bulldogs, the condition is caused by a mutation in the CTSD (cathepsin D) gene. The mutation prevents the breakdown of cellular waste in neurons, leading to progressive accumulation of lipofuscin pigment and eventual neuronal death. The clinical course is gradual, progressive, and fatal.

Symptoms and timeline

Affected American Bulldogs are typically born appearing healthy. Symptoms emerge between 18 months and 4 years of age and include:

Loss of coordination, especially in the hind end
Behavioral changes (anxiety, fearfulness, loss of trained behaviors)
Cognitive decline, "lost" episodes
Vision loss progressing to blindness
Seizures in advanced disease

The disease progresses over months to a few years. There is no treatment that halts or reverses the progression. Most affected dogs are euthanized within 12-24 months of symptom onset for quality-of-life reasons.

How testing works

The CTSD mutation is identified by simple cheek-swab DNA testing. The Embark genetic panel includes NCL testing as part of its standard breed-specific health panel. Other testing labs (UC Davis VGL, Animal Genetics) also offer the test.

Result categories:

Clear (N/N): Two copies of the normal gene. Will not develop disease. Cannot pass affected status to offspring.
Carrier (N/M): One copy of the mutation. Will not develop disease. Can pass the mutation to 50% of offspring.
Affected (M/M): Two copies of the mutation. Will develop disease.

How responsible breeders use the test

The breeding rules are straightforward:

Test every breeding dog. Without testing, the breeder is gambling.
Clear-to-clear pairings: 100% of puppies are clear. No risk.
Clear-to-carrier pairings: 50% clear, 50% carrier. No affected puppies. Acceptable when one of the dogs is breeding-quality on every other measure.
Carrier-to-carrier pairings: 25% clear, 50% carrier, 25% affected. Never acceptable. Any breeder who does this is producing dogs that will die of NCL.
Disclosure: Buyer should see both parents' test results before deposit.

Questions to ask any American Bulldog breeder

"Are both parents NCL tested? May I see the test reports?"
"What is each parent's NCL status: clear, carrier, or affected?"
"If either parent is a carrier, what is the other parent's status?"
"Will my puppy come with its own NCL test result?" (Many established breeders test puppies before placement; some leave it to the buyer.)

A breeder who can't or won't answer these questions is selling you a gamble.

Rosebull's NCL protocol

Every Rosebull breeding dog runs the full Embark genetic panel. NCL status is on file for every parent in our breeding program. Pairings are planned to ensure no Rosebull puppy can be NCL-affected. Test reports are shared with buyers on request and are linked from each parent dog's page on this site. Read more on our health testing protocol page.