From the Universities Federation for Animal Welfare
Polycystic Kidney Disease
Related
terms: autosomal dominant polycystic kidney disease (AD-PKD)
Outline:
Polycystic kidney disease affects about one in three Persian cats. A genetic
fault in kidney cell development leads to multiple cysts forming in the
kidneys. These grow and eventually cause kidney failure. Often this is not
until after breeding age has been reached but it can be much sooner. The
disease is progressive and there is no cure, but treatment can alleviate it in
the early stages. Kidney failure causes malaise and inappetance and, in later
stages, muscle weakness, vomiting and seizures, and so is likely to cause
unpleasant feelings of moderate to severe intensity. Affected animals can be
detected and should not be used for breeding. The prevalence of this disease is
declining because of testing and it should be possible to eliminate it.
Summary of Information
(for
more information click on the links below)
1.
Brief description
Polycystic
kidney disease (PKD) is characterised by the presence of multiple fluid-filled
sacs or cysts in the kidneys. They can be present at birth but initially are
microscopic and enlarge throughout life. The rate of growth varies but, at some
stage, chronic renal failure (CRF) occurs as the enlarging cysts damage normal
kidney tissue. Typical signs of PKD are those also associated with chronic
renal failure reduced appetite, weight loss, increased thirst and urine volume,
muscle weakness, vomiting, seizures (fits) and death.
2.
Intensity of welfare impact
Renal
failure causes malaise and inappetance and, in later stages, muscle weakness,
vomiting and seizures. These are likely to cause unpleasant feelings of a
moderate to severe intensity. Treatment can help to control the disease
but treatment can itself have adverse welfare consequences. For example,
special diets may be of low palatability, frequent administration of tablets
may be aversive, as may frequent travel to and from veterinary practices and
veterinary interventions.
3.
Duration of welfare impact
Most
cats affected with PKD will have a normal life until signs of CRF occur. Once
signs associated with CRF appear they will persist until death. This may be
weeks or years. During this period the welfare impact will vary from mild to
severe depending on the stage of disease and the effectiveness of any
treatments.
4.
Number of animals affected
PKD has been very common in Persian
cats. Around 36-49% of all Persians have been reported to have the condition
(Cannon et al 2001, Barrs et al 2001, Beck & Lavelle 2001, Barthez et al 2003, Cooper 2000, Bonazzi et al 2007. Domanjko-Petri et al 2008, Bonazzi et al 2009). However, the number with the
condition may be decreasing due to the effectiveness of ongoing control
schemes. It is believed to be the commonest genetic disease in cats.
Breeds related to Persians:
Himalayans, Exotic shorthairs, Ragdolls, and Chinchillas, have also been shown
to be affected by the condition (Barrs et al2001).
5.
Diagnosis
The
diagnosis of renal failure (CRF) rests upon clinical examination and the
results of laboratory tests. The presence of the cysts in the kidneys can be
detected by ultrasound examination which can indicate the presence, number and
size of the cysts within each kidney. This method of detection is most
sensitive when the cat is over 10 months of age. A genetic test is available
which detects the presence or absence of the PKD1 genetic mutation that
underlies the disease.
6.
Genetics
The form of PKD detailed here is an
autosomal dominant condition with variable penetrance (Biller et al 1990, Biller et al 1996). The affected gene is PKD1
(Lyons et al 1994).
7.
How do you know if an animal is a carrier or likely to become affected?
In
contrast to conditions caused by recessive genes, all cats with the gene will
be affected and will go on to develop signs of the disease in due course.
However, although strictly there is therefore no carrier state, the disease
tends not to manifest until relatively late in life and often not until after
breeding age. It is therefore necessary to use special tests to detect affected
animals before breeding age. Both ultrasound examination after 10 months of age
or use of the genetic test after weaning are reliable in identifying affected
and unaffected animals and combining both has its advantages.
8.
Methods and prospects for elimination of the problem
All
cats that carry the abnormal gene are affected with AD-PKD and this makes it
relatively easy to eliminate the disease from a breeding group. If all cats in
the high-risk breeds were to have their kidneys scanned or be gene tested
before they were used for breeding, and if affected cats were not then used for
breeding, PKD could be eradicated in a single generation. This would, however,
significantly decrease the number of cats within the Persian breed which could
be bred from, and hence restrict their gene pool. Such a restriction could
increase the risk of other diseases with genetic influences.
For
further details about this condition, please click on the following:
(these link to items down this page)
(these link to items down this page)
·
Genetics
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