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We group breeding programs into three levels based on testing depth. Ask your breeder directly which level they meet.
A breeder at the Great level performs all mandatory tests plus 9 additional clinically recommended screenings that reduce risk in this breed.
In addition to mandatory tests:
Apple head
Allgemeine Fitness und Anatomie
Apfelkopf, or apple head, describes an extremely rounded, dome-like skull shape with a very pronounced forehead angle, or stop. This skeletal variation affects the structure of the head and can predispose dogs to open fontanelles, which are soft spots where the skull bones fail to close fully. In some cases, this shape can also restrict fluid flow in the brain, leading to a buildup of fluid known as hydrocephalus.
Physisch · Passing: no apple head
Ectropion / Entropion
Augen
These are structural eyelid abnormalities affecting a dog's eyes. In cases of entropion, the eyelid rolls inward, causing the eyelashes or fur to rub painfully against the surface of the eyeball. In ectropion, the eyelid sags or rolls outward, leaving the sensitive inner lining of the eye exposed and unprotected.
Passing: CLEAR
Progressive Retinal Atrophy (PRA)(PRA)
Augen
Progressive Retinal Atrophy (PRA) is an inherited eye disease that affects the retina, which is the light-sensitive layer of tissue at the back of the eye. In this condition, the specialized cells responsible for detecting light, known as photoreceptors, gradually degenerate and die. Because these cells cannot recover or be replaced, the disease slowly but inevitably leads to complete blindness.
Passing: CLEAR
Retinal Dysplasia(RD)
Augen
Retinal dysplasia is a congenital condition affecting the eyes, where the retina (the light-sensitive tissue at the back of the eye) does not develop properly during growth in the womb. This abnormal development leads to structural defects like folds or gaps in the retinal layers. Because the retina is responsible for sending visual signals to the brain, these imperfections can impair normal vision.
Augen · Passing: CLEAR
Primary Open-Angle Glaucoma(POAG)
Augen und Sehvermögen
Primary open-angle glaucoma is an inherited eye disease where the natural fluid inside the eye cannot drain properly. This fluid buildup causes a gradual increase in pressure within the eyeball, which eventually damages the optic nerve, the connection between the eye and the brain. Without management, this pressure leads to permanent blindness.
Augen · Passing: CLEAR
Lens luxation(PLL)
Augen und Sehvermögen
Lens luxation is an inherited eye disorder where the lens slips out of its normal position because the supporting fibers holding it in place weaken or break. When the lens shifts, it can block the natural drainage of fluid within the eye. This blockage causes a rapid, painful buildup of pressure called glaucoma, which can lead to permanent blindness if left untreated.
Augen · Passing: Clear or Carrier
Cerebellar Ataxia(CA1)
Nervensystem
Cerebellar Ataxia is an inherited neurological disorder that affects the cerebellum, which is the part of the brain responsible for coordinating movement and balance. Due to an autosomal-recessive genetic mutation, nerve cells in this brain region progressively degenerate. This gradual loss of cells prevents the brain from properly controlling the body's movements.
DNA · Passing: Clear or Carrier
Cranioschisis
Zähne und Knochen
Lückenschädel is a congenital developmental defect affecting the skeletal system, specifically the skull. It occurs when the bones of the cranial vault fail to harden or ossify completely, leaving thin spots, depressions, or actual gaps in the bone structure. This defect is often associated with increased pressure within the skull and other brain abnormalities.
Roentgen · Passing: A
Spinocerebellar Ataxia(SCA)
Spinocerebellar ataxia is an inherited neurological disorder affecting the dog's nervous system, specifically the spinal cord and the cerebellum, which is the brain region responsible for coordinating movement. Over time, the nerve cells in these areas degenerate and fail to communicate properly. This results in a progressive loss of control over bodily movements.
Passing: Clear or Carrier
These levels are a comparison framework, not an official certification. They help compare breeding programs at a glance.
A complete checklist with every mandatory and recommended test plus identity and rearing questions — take it with you.
Open the full checklistFor breeders
Machine-readable mating rules, minimum ages, scoring schemes, and what's required for HonestDog verification — as a printable guide.
Example rule — Cataract
Both parents must be CLEAR or better.
We compile mandatory tests from official breed regulations and veterinary databases — and check every uploaded certificate for authenticity.
L1 = mandatory under breed-club regulations. L2 = recommended or clinically indicated. L3 = lower prevalence. Every assignment carries a source and confidence rating.
VDH-Zuchtordnungen, CIDD (University of PEI), OMIA (University of Sydney), curated veterinary input.
Uploaded certificates are AI-extracted and reviewed by our team for authenticity, date, and result.
12 tests are currently mandatory under the relevant breed-club regulations. The most common are DNA-Identitätsnachweis, Ocular anomalies, Hereditary Cataract (HC). Every test must be completed before mating, and the result must fall within the threshold defined by the regulation.
See breeders who have already uploaded their mandatory tests for verification.
View verified breedersHealth Testing Guide
Which tests are mandatory, how to spot responsible breeders — and what it costs when things go wrong.
For the Jack Russell Terrier we have compiled 12 mandatory and 9 recommended health tests, drawn from breed-club regulations, the University of PEI (CIDD), and OMIA — weighted by severity and heritability.
What this grade means
While the Jack Russell Terrier is considered a robust working dog, it carries a higher-than-average genetic predisposition for eye conditions such as Progressive Retinal Atrophy (PRA) and glaucoma. Patellar luxation is also a known joint weakness, though it can be effectively managed through strict breeding tests. Prospective buyers should therefore pay close attention to the health screening results of the parent dogs to avoid any unpleasant surprises.
Every breed is susceptible to certain inherited conditions. Just like humans, dogs inherit predispositions from their parents. Responsible breeders screen their breeding dogs for these conditions and make informed mating decisions to reduce the risk passed on to puppies.
No — but it's the strongest tool we have. Diet, exercise, environment, and genetics all contribute to whether a dog develops a condition. When breeders use the right tests to identify risk in potential parents, the likelihood of many conditions appearing in the puppies drops significantly.
There's no one-size-fits-all here. For the Jack Russell Terrier we track 12 mandatory tests plus 9 additional recommended ones. The specific tests and passing thresholds are detailed further below.
Keep in mind
Reliable screening tests still don't exist for many hereditary conditions, and tests for complex polygenic conditions are not always predictive of severity in the puppies. Even so, they're a powerful tool used by every responsible breeder.
There are two main types of health tests:
Screen the dog's DNA for known disease-causing mutations. Can be performed from puppyhood and give a binary result (clear / carrier / affected).
Clinical and imaging exams like X-ray, ultrasound, or ophthalmoscopy. They show how a predisposition actually manifests — usually only conclusive after 12–18 months.