Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

Munchkin

Munchkin

Limb Deformity

Related terms: achondroplasia, chondrodysplasia

Outline: Due to a deleterious genetic mutation, the limb bones of Munchkin cats fail to grow normally. Because of their resulting short legs, the behaviour of these cats is affected and they may be predisposed to painful osteoarthritis. A proportion of kittens born to Munchkin parents dies prior to birth because of this serious genetic mutation. Many breed clubs refuse to recognise this breed. We suggest that, because of risks to quality of life, cats with this abnormality should not be used for breeding.


Summary of Information

(for more information click on the links below)

1. Brief description

The Munchkin abnormality results in greatly shortened fore and hind limbs. This compromises the ability of affected animals to jump and may, possibly, increase their risk of joint disease. Short limbs are a key feature of the breed standards of both long and short-haired Munchkin cats. 

The welfare aspects of this abnormality have not been evaluated in the scientific literature as far as we are aware and are hard to assess. Affected animals may experience abnormal stresses and loads on their joints which can increase the risk of painful osteoarthritis.

2. Intensity of welfare impact

Munchkins have difficulty in moving normally, and thus behaving as other cats. It is hard to assess the effect this has on welfare. When it leads to osteoarthritis, the condition causes pain and further dysfunction.

3. Duration of welfare impact

The disabilities caused by these abnormalities are present from birth. Affected cats can adapt and may learn how to minimise the impact of the abnormalities on their movement to some extent. However, when joint degeneration occurs this is likely to cause pain and further disability. Osteoarthritis can be treated with painkillers but side effects from the drugs are quite common, especially when concurrent disease is present (Ramsey 2011).

4. Number of animals affected

All Munchkin cats are affected.

5. Diagnosis

The characteristic abnormality of Munchkin cats is obvious, on examination, from birth, but the extent of the resulting disability may only be evident as the cat matures. Detection of osteoarthritis and the assessment of its severity may require radiography (x-rays) or trial treatment (Godfrey 2011).

6. Genetics

The Munchkin deformity is thought to be caused by a dominant, lethal gene with variable penetration. Kittens in which both copies of the gene are of the abnormal form are thought to die before birth. Animals with only one copy (ie those that are heterozygous) show the deformity.

7. How do you know if an animal is a carrier or likely to become affected?

On examination, affected cats show obvious deformity.  All cats with the affected gene are affected so it appears that there are no symptom-less carriers of the gene.

8. Methods and prospects for elimination of the problem

Many pedigree cat associations around the world have refused to recognise the Munchkin (http://www.gccfcats.org/pdf/health.pdf) but their breeding is being encouraged by some organisations. For welfare reasons, we recommend that affected cats should not be used for breeding.


For further details about this condition, please click on the following:
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1. Clinical and pathological effects

The Munchkin abnormality results in abnormally short fore and hind limbs, like those of short-limbed dog breeds such as Dachshunds and Bassett hounds. Hartwell (no date) has reviewed the history of reports of short-legged mutant cats (http://www.messybeast.com/shortlegs.htm). Short limbs are a key feature of the Munchkin breed standards of both long and short-haired Munchkin cats, although breed standards allow hind legs to be longer than forelegs (http://www.tica.org/members/publications/standards/mk.pdf).

The welfare aspects of this abnormality have not been evaluated and are hard to assess. Affected animals may experience abnormal stresses and loads on their joints which may cause pain.

The abnormality appears to be due to a failure of normal growth of the long bones of the limbs. The knock-on consequences of the resulting abnormal conformation have not been well established. It is known that animals that experience abnormal stresses and loads on joints are predisposed to developing osteoarthritis (Bennett & May 1995) and, since this is common in older cats of all breeds (Godfrey 2005), it seems likely that Munchkin cats may be particularly at risk.

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2. Intensity of welfare impact

The impacts of this condition depend on its severity. There are reports of Munchkin cats having reasonably normal levels of activity but even advocates of the breed acknowledge that their ability to jump is affected (http://www.tica.org/public/breeds/mk/intro.php).

When osteoarthritis occurs this causes pain and is likely to further compromise function.

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3. Duration of welfare impact

The disabilities caused by these abnormalities are present from birth. Affected cats may adapt and learn how to manage or overcome the abnormalities to some extent. When joint degeneration occurs this is likely to cause pain and further disability. Osteoarthritis can be treated with painkillers but side effects from the drugs are quite common, especially when concurrent disease is present (Ramsey 2011).

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4. Number of animals affected

All Munchkin cats are affected. We are unaware of data on the world population sizes of these cats.

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5. Diagnosis

The characteristic abnormality of Munchkin cats is obvious, on examination, from birth, but the extent of the resulting disability may only be evident as the cat matures. Detection of osteoarthritis and the assessment of its severity may require radiography (x-rays) or trial treatment (Godfrey 2011).

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6. Genetics

The Munchkin deformity is thought to be caused by a dominant, lethal gene with variable penetration. Kittens in which both copies of the gene are of the abnormal form are thought to die before birth. Animals with only one copy (ie those that are heterozygous) show the deformity. Since Munchkin cats have one normal and one abnormal copy of this gene, a proportion of kittens will inherit the abnormal forms from both parents (and will die before birth) and a similar proportion will inherit two normal forms and will avoid the disease altogether (http://www.tica.org/public/breeds/mk/intro.php). The majority will, however, have inherited the condition.

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7. How do you know if an animal is a carrier or likely to become affected?

On examination, affected cats show obvious deformity. All cats with the affected gene are affected so it appears that there are no symptom-less carriers.

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8. Methods and prospects for elimination of the problem

Many pedigree cat associations around the world have refused to recognise the Munchkin (http://www.gccfcats.org/pdf/health.pdf) but their breeding is being encouraged by some organisations.  The breed has been advocated by some because of the qualities of its coat and personality but there is no evidence that these features are directly linked to the limb deformity and so breeding from Munchkin-derived cats with normal legs may preserve these neutral or beneficial characteristics while eliminating the deformity that has no benefit for the affected cats (http://www.tica.org/public/breeds/mk/intro.php). However, since the genetic basis of this problem has not been well defined there may be risks with this approach. It may therefore be safer to avoid breeding even from cats with apparently normal conformations that have been born to Munchkin parents.

The fact that similar deformities are well established and accepted (by some) in other domestic breeds (for example in dogs, Basset hounds and Dachshunds) has been used to justify the creation and perpetuation of Munchkin cats (http://www.tica.org/public/breeds/mk/intro.php). Others have argued against this, for example: “…our consensus is that the basic design of the domestic cat is fundamentally sound. Why mess with it?” (Malik et al 2009). Because of possible adverse effects on quality of life we suggest that cats with the Munchkin abnormality should not be used for breeding.

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9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.

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10. References

Bennett D and May C (1995) Joint diseases of the dog and cat. In Ettinger SJ & Feldman EC (Eds) Textbook of Veterinary Internal Medicine 4th edition. Saunders, Philadelphia pp 2054

Godfrey DR (2005) Osteoarthritis in cats: a retrospective radiological study. Journal of Small Animal Practice 46: 425-429

Godfrey DR (2011) Diagnosis and management of osteoarthritis in cats. In Practice 33: 380-85

Hartwell, S (no date) Short-legged cats.
http://www.messybeast.com/shortlegs.htm accessed 9.1.2012

Malik R, Sparkes A and Besant C (2009) Brachycephalia – a bastardisation of what makes cats special. Journal of Feline Medicine and Surgery 1: 889-90

Ramsey I (2011) Meloxicam. In: BSAVA Small Animal Formulary 7th Ed. British Small Animal Veterinary Association, Gloucester, UK 216-7

http://www.gccfcats.org/pdf/health.pdf accessed 15.9.2011

http://www.tica.org/public/breeds/mk/intro.php accessed 15.9.2011

http://www.tica.org/members/publications/standards/mk.pdf accessed 15.9.2011

© UFAW 2011


Credit for main photo above:

http://depositphotos.com/30032973/stock-photo-munchkin-kitten-outdoors.html
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