Rat Terrier Health Problems: Breed Risks for Owners

Rat Terriers are prone to a recognisable cluster of conditions: patellar luxation, Legg-Calve-Perthes disease, cranial cruciate ligament injury, primary lens luxation and other eye disease, allergic skin disease and demodectic mange, hypothyroidism, degenerative mitral valve disease, and crowded teeth that lead to gum disease. If your dog is limping, squinting, scratching themselves raw, coughing or simply not acting like themselves, book a veterinary exam rather than waiting to see whether it settles on its own. A dog that cannot bear weight on a leg, has a suddenly cloudy or painful eye, is struggling to breathe or collapses needs emergency veterinary care straight away.

The breed is a sturdy, athletic working terrier, and plenty of Rat Terriers go through life with nothing more dramatic than a dental cleaning. But no breed is risk free, and the value of a breed-risk list is not worry. It is knowing the shape the problems tend to take, so you recognise the first signs and get them looked at while they are still small.

Joint and bone conditions the breed is known for

Orthopaedic problems are where owners notice something first, usually because the dog changes how it moves.

Patellar luxation is the classic small-breed knee problem. The kneecap slips out of its groove in the thigh bone, and the dog skips a step or two on a hind leg, carries it for a moment, then drops back into a normal stride as the kneecap pops home. Some dogs sit with one hind leg stuck out to the side. Your vet grades the looseness by feel during an exam and decides whether monitoring, physical rehabilitation or surgical correction is appropriate.

Legg-Calve-Perthes disease affects the head of the femur where it sits in the hip socket in young small-breed dogs. The bone's blood supply falters and the joint surface deteriorates, which is painful. Signs build gradually: a worsening limp on one hind leg, muscle on that thigh looking smaller than the other side, snapping or flinching when the hip is extended, and reluctance to jump. It is diagnosed on radiographs, and treatment is surgical.

Cranial cruciate ligament injury tends to show up differently: a sudden yelp during a turn or a landing, then toe-touching or non-weight-bearing lameness on a hind leg. Knee instability does not resolve by itself, and the opposite knee carries extra load while the injured one is sore, so prompt assessment matters.

Hip dysplasia is less associated with small breeds than large ones, but it is seen. Watch for a swaying rear gait, bunny-hopping when running, stiffness after rest and difficulty rising.

Subtle pain signs are worth taking as seriously as an obvious limp: hesitating at the couch or the car, slowing on the back half of a walk, licking at one joint, a hunched or shifted posture, or new irritability when touched. Talk to your veterinarian before giving anything for pain. Many human pain relievers are dangerous for dogs even in small amounts.

Eye conditions: lens luxation, cataracts and vision loss

Primary lens luxation is an inherited condition recognised in several terrier types, including the Rat Terrier. The fibres holding the lens in place weaken, the lens shifts out of position, and it can block the normal drainage of fluid inside the eye, which drives pressure up and causes glaucoma. That is a painful, vision-threatening situation.

Signs to act on: squinting, a watery or red eye, a cloudy or oddly shimmering appearance to the eye, rubbing the face on the carpet, pawing at the eye, pupils that look unequal, or a dog that suddenly avoids bright light. Treat any of these as a same-day veterinary call, and say on the phone that you are worried about the eye. Pressure inside the eye can be measured in minutes, and the window for preserving comfort and sight is short.

Cataracts and progressive retinal atrophy present more quietly. Owners describe a dog bumping into furniture that has been moved, hesitating at stairs or doorways, becoming reluctant to go out after dark, or standing still in unfamiliar rooms. A cloudy or bluish look to the lens is worth an exam, partly because not every cloudy eye is a cataract and the differences matter.

Skin, ear and coat problems

Allergic skin disease is one of the complaints owners raise most about this breed. Environmental allergies, flea allergy and food reactions all produce a similar picture: paw licking and chewing, red skin in the armpits, belly and groin, head shaking, dark or smelly ears, repeat ear infections, hair loss from self-trauma, and thickened or discoloured skin in long-standing cases. Short-coated dogs also show nicks, scrapes and sunburn-prone spots more readily.

Demodectic mange is caused by mites that live on normal skin and overgrow when the immune system is immature or stressed. It tends to appear in young dogs as patchy hair loss around the eyes, muzzle or forelegs, with skin that may look scaly rather than itchy unless a bacterial infection has set in on top. A skin scrape in the clinic confirms it quickly.

This is an area where home guesswork costs time. Itching has many causes that look identical from the outside, and products meant for people, or for other species, can make things worse. Talk to your vet about which type of itch you are dealing with before changing anything.

Heart, hormone and internal conditions

Degenerative mitral valve disease is a small-breed concern in general. The valve between the left atrium and left ventricle thickens and stops sealing, which a vet hears first as a murmur during a wellness exam, long before the dog feels different. Later signs include a soft persistent cough, tiring on walks, a faster resting breathing rate while asleep, restlessness at night, a swollen belly, or fainting. Laboured breathing or collapse is an emergency.

Hypothyroidism develops slowly and is easy to mistake for ageing. Owners notice weight gain without a change in feeding, a dull or thinning coat, flaky skin, hair loss along the flanks or tail, seeking out warm spots, and a general flattening of energy. A blood panel sorts it out, and it is managed medically under veterinary supervision.

Other internal problems are not breed-specific but still belong on your radar because any dog can develop them: new lumps under the skin, increased drinking and urinating, vomiting or diarrhoea that persists, unexplained weight loss, a distended abdomen, or seizures. Any new lump should be checked by a vet, and only a needle sample can tell what it is.

Teeth, body condition and the exam room habit that catches things early

Rat Terriers have compact jaws, and crowded or rotated teeth trap plaque where a toothbrush struggles to reach. Retained baby teeth, tartar build-up and periodontal disease follow, and the signs owners spot are bad breath, dropping kibble, chewing on one side, bleeding or receding gums, pawing at the mouth and reluctance to let you touch the face. Gum disease is painful and it does not improve without professional care. Your vet assesses the mouth at wellness visits and advises when a full dental examination under anaesthesia with radiographs is needed.

Body condition is the other lever in your hands. Extra weight increases the load on knees and hips that may already be structurally imperfect, and it makes allergic skin and heart disease harder to manage. Ask your vet to score your dog's body condition at each visit and show you how to assess ribs and waist yourself. Strength and conditioning matter too: a well-muscled dog supports its own joints better than a soft one.

Condition	What owners notice	When to contact a vet
Patellar luxation	Skipping steps, holding a hind leg up briefly, sitting with a leg out	At the next available appointment, sooner if the limp persists
Legg-Calve-Perthes disease	Worsening hind leg lameness in a young dog, thigh muscle wasting	Within days, this is a painful joint
Cruciate ligament injury	Sudden yelp then toe-touching or non-weight-bearing lameness	Same day
Primary lens luxation	Squinting, red or cloudy eye, face rubbing, light avoidance	Same day, say it is the eye when you call
Cataracts or retinal degeneration	Bumping into things, hesitating at stairs, poor night vision	Within days
Allergic skin disease	Paw licking, red belly, head shaking, repeat ear infections	At the next appointment, sooner if ears are painful
Demodectic mange	Patchy hair loss around eyes, muzzle or forelegs	Within days
Hypothyroidism	Weight gain, coat thinning, low energy, seeking warmth	At the next appointment
Mitral valve disease	Murmur found at exam, cough, tiring, fast resting breathing	Same day for breathing changes, emergency for distress
Periodontal disease	Bad breath, dropping food, bleeding gums, mouth pain	At the next appointment

Key Takeaways

• The joints are the headline risk: patellar luxation, Legg-Calve-Perthes disease and cruciate ligament injury all change how the dog moves before they change anything else.
• Any sudden eye change in a terrier deserves a same-day call, because primary lens luxation can raise pressure inside the eye and that is painful and sight-threatening.
• Itching, ear infections and paw licking point to allergic skin disease or mites, and the two look identical without a veterinary exam.
• A heart murmur, slow weight gain or a thinning coat are found at wellness visits long before the dog seems unwell, which is the entire argument for keeping those visits.
• Crowded teeth and extra body weight are the two risk factors most within your control, and both are assessed in the exam room.
• Breathing difficulty, collapse, non-weight-bearing lameness, a painful eye or a seizure are emergencies, not wait-and-see situations.

Where your veterinarian fits in

A breed-risk list tells you what to look for. It cannot tell you what your dog has. Only a veterinary examination, with the hands-on assessment, imaging and blood work that go with it, can turn a limp, a cloudy eye or a cough into an actual diagnosis and a treatment plan. The vet owns both of those, and everything else, from conditioning and weight management to home monitoring, works around the plan they set.

Practical things you can do: keep a short note of what you see and when, take a phone video of an intermittent limp or an odd gait because it may vanish in the waiting room, bring a list of everything your dog eats and receives, and keep wellness visits even in years when nothing seems wrong. Results vary from dog to dog, two Rat Terriers with the same condition can need very different plans, and talk to your vet about anything new before you act on it at home.

Related reading: Dog Emergency Signs covers the changes that mean stop and get help now rather than booking for later.