Giant Schnauzer Health

What is HUU?

Hyperuricosuria is an inherited condition that causes excessive uric acid level in a dog’s urine. Uric acid is a waste product that is normally excreted by the kidneys. High levels of uric acid leads to the formation of crystals in the urine causing kidney and bladder stones (urate stones). These stones can cause inflammation and irritation, and can also block the drainage of urine causing severe pain, high blood potassium levels and the risk of kidney failure. In some cases the stones require surgical removal  and can be life-threatening, especially in male dogs if the urinary tract becomes blocked by urate stones.

Prevalence

Data provided by Laboklin (2024) from across Europe, including the UK, shows that 36% of Giant Schnauzers carry one copy of the HUU (SLC2A9) mutation, and 4% are genetically affected having 2 copies of the mutation.

Age of Onset

The changes in the urine are generally present from birth, however it usually takes some time for crystals to form and combine into stones that cause problems, most often between three and six years of age.

Mode of Inheritance

The disease is believed to be an autosomal-recessive condition. This means that dogs that inherit two copies of the gene mutation (one from its mother and one from its father) will have an increased risk of developing the disease.

Signs & Symptoms

Prior to forming stones, dogs may show no clinical signs of disease.

In dogs that form urate stones, the most common signs include:

• Straining to urinate
• Frequent, small amounts of urination
• Accidents in the house
• Blood in the urine
• Decreased appetite

The inability to urinate may occur if stones develop and cause an obstruction in the urethra, which is a medical emergency. The signs of this condition will be much more severe — including a large and firm bladder, abdominal pain, vomiting and lethargy. Both male and female dogs can be affected, but obstruction of urine flow is more common in males due to differences in anatomy. If left untreated, a urinary obstruction can be fatal.

Diagnosis

Hyperuricosuria can be diagnosed by ultrasound or urine sediment analysis (urate stones are less dense and may not be visible on x-rays). The available DNA test may be used to differentiate between urate stones caused by hyperuricosuria and other conditions.

Prognosis

The prognosis for HUU depends on the size and number of stones. Some affected dogs may show no clinical signs, whereas others require treatment. Small stones may be flushed out with a urinary catheter. Larger stones can block the urinary system leading to rapidly progressive, severe problems and even death due to kidney failure and high blood potassium levels. Blockage of the urinary system can rapidly become a medical emergency, often requiring surgery to save life. Affected dogs require a low purine diet to help minimise the formation of uric acid and therefore the formation of stones. Increased water intake is also often recommended. The medication allopurinol may be prescribed in some cases.

To comply with the Kennel Club’s ‘Best Practice’ breeders should DNA test for HUU prior to breeding

Where to go for a DNA Test

See the list of KC approved DNA testing laboratories:

Costs

The Giant Schnauzer Club have a discount voucher code for the Laboklin Giant Schnauzer bundle which consists of: HUU, prcd-PRA, DCM, PRA5 & DM

Contact the breed health co-ordinator for more information

Requirements for the DNA test

1. The dog should be microchipped
2. The Kennel Club require at least two forms of identification on the result certificate. These must include the dog’s microchip or tattoo number along with either the dog’s registered name or their registered number.
3. Results must be of a recognised DNA test and from an approved laboratory for the result to be officially recorded by the KC.

Publication of Results

HUU is now part of the official KC DNA Testing Scheme, and as such DNA test results can be added to the KC database for official reporting.

Advice for Puppy Buyers

Ideally choose a breeder where the sire and dam have been DNA tested. If one parent is a carrier or affected the other parent must be CLEAR.

Two carriers, two affected, or a carrier and an affected should not be bred together, as this will produce affected puppies.

Ask the breeder to provide information on the DNA status of a puppy and/or both parents. You can also check on the Kennel Club website link below.

Kennel Club Health Test Result Finder

DNA test results are published for this condition via the Kennel Club health test results finder.

Advice for Breeders

In order to meet the Kennel Club’s ‘Best Practice’ Breeders should DNA test for HUU before breeding.

If you have already had your Giant HUU DNA tested you can now send the results to the KC for officially recording.

Email test certificates to: health.results@thekennelclub.org.uk

Data from Laboklin shows that 36% of Giant Schnauzers carry the HUU mutation, therefore it is important to test before breeding to know which dogs are carriers, and be able to breed safely. If you haven’t tested it’s not possible to know!

The DNA test can prevent puppies from being affected by this mutation.

The mode of inheritance for HUU is a simple autosomal recessive gene. Therefore both the parents that produced an affected puppy would either have one or two copies of the mutant gene.

See breeding from a DNA Tested Dog

The probabilities of producing affected puppies from a simple autosomal recessive inheritance are shown below (actual numerical values will vary)

A ‘Clear‘ has 2 copies of the normal gene, is unaffected and cannot pass on a faulty gene.

A ‘Carrier‘ has 1 normal gene and 1 recessive abnormal gene, they are physically unaffected but may pass on the abnormal gene.

‘Affected‘ dogs have 2 copies of the defective gene of which they will pass on 1 of the affected genes to their offspring.

A mating that may produce affected puppies should not be carried out.

Make a Donation to the GSHF

The purpose of the GSHF is to provide monies for research into inherited health problems in the Giant Schnauzer. All donations gratefully received.

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