Health Problems In Cloned Cats (and other mammals)

Cloned cat CC

Cloned cat CC – Photo By Karen Warren/Houston Chronicle

This follow-up page covers health and other issues of cloned mammals and follows Ruth’s article questioning whether people should clone their cat, even if they could afford it.

I think it is useful to briefly look at the difficulties of cloning cats. This of course is ignoring the seeming impossibility of cloning a cat’s personality. I think that aspect of cloning itself is enough to question the process and is the main point raised in comments to Ruth’s article. It is worth noting that the first cloned cat was a female calico cat (“CC”), who looked very different to her mother. The color and pattern of coats of cats are not exclusively dependent upon the genes of the cat.

Health Problems

In 2002 survey published in the science journal Nature Biotechnology, it was found that in animals cloned through what is called nuclear transfer (transplanting the nucleus of one cell into another), almost a quarter of all cloned mammals failed to reach healthy adulthood. In addition, the survey showed that the health problems in cloned animals were wide-ranging from mild to fatal and included1:

  • Heart defects
  • Liver fibrosis
  • Respiratory failure
  • Obesity
  • Anaemia

In 2003 the first cloned mammal, Dolly, a sheep, was euthanised because of a lung tumour. It was caused by a virus. Although, in defence, it was said that there was no evidence that the cloning was a factor in the disease.

In addition to those mentioned above, health problems are2:

  • Sometimes (scientists don’t know when it will occur): an increase in birth size (Large Offspring Syndrome – LOS). These animals have large organs, which can lead to health problems.
  • A variety of defects in vital organs such as liver, brain and heart.
  • Problems with the immune system.
  • Premature aging. Dolly, the cloned sheep mentioned above died when she was 6 years old, which is about half the average age of the lifespan of sheet. That said, the 1st cloned cat, CC, at May 17, 2011, was 10 years of age. I don’t know how much longer she lived beyond that date. Dolly’s shorter than average lifespan was due to shortened chromosomes because the ends of the chromosomes have shrunk more than usual on cloning (as I understand it).

CC was treated like any other cat by her caretaker, Shirley Kraemer. CC had a litter of 4 kittens one of which was stillborn while no health issues were detected in the remaining kittens3.


Using clones in a breeding program results in inbreeding which in turn increases the possibility of offspring being unhealthy.

Failure Rate

When animals are cloned through somatic cell nuclear transfer there is a high failure rate. The success rate ranges from 0.1% to 3%. This means that out of 1000 attempts there may only be one successful clone4.

Gene Expression

In natural development, the time at which a gene expresses itself in the appearance etc. of the animal is dictated by the nucleus of the cell, which is programmed. In cloned animals the transferred nucleus does not have the same programming and therefore there is a question mark over whether the clone will express the right genes at the right time? This is still an unknown4.


Are there any conservation benefits in cloning wild cat species? Two African wildcat clones gave birth to cubs in around 2004 at the Audubon National Institute Of New Orleans. It was described as a triumph but I cannot find information about how well the kittens developed. The conservation value is dubious. Dr Lieberman director of WWF’s Species Programme says that cloning has no value for conserving endangered species in the wild. In fact it is a process of failure of conservation in the wild as far as I am concerned. The process seems to be more about scientists experimenting with mammals as an academic exercise rather than having the objective of ensuring the existence of endangered species.


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Health Problems In Cloned Cats (and other mammals) — 12 Comments

  1. This is very interesting Michael and adds to our previous articles.
    What worries me is, how many cloned animals are killed at birth by the scientists doing this, because they are not born perfect? Are they killed or are they experimented on to find out why? How many animals suffer in experiments to ‘perfect’ cloning?
    Animals suffer in labs every day in many ways, this is just one more way to cause suffering in order to be the first to succeed in playing God!

    • I see it as an academic exercise by scientists who just like to test things and challenge things, which, as far as I’m concerned is the wrong attitude. I agree that we don’t know how many cloned animals and cats have grown up to only die young and in discomfort or pain. Those sorts of statistics are not available on the Internet. I suppose they are kept in-house close to the chest of the scientists of the scientists.

      Another aspect of cloning that I dislike is that it is being turned into a commercial exercise despite the fact that it is early days and the outcome is uncertain. This is an unpleasant development that, I am sure, concerns a lot of people.

      I’m convinced that the vast majority of people including cat owners dislike cloning. They will agree with us and it has not turned out to be a commercial success, thankfully.

  2. Totally right-on Michael!

    Cloning is not only dangerous, isn’t it also (mainly for pet guardians who would clone a beloved pet) just a form of denial about the eventual death of the animal? Or trying to have that animal live forever? I hate the idea.

    • My friend, Jo. This is exactly what I have been trying to convey on PoC since I “hooked up.” Denial Don’t think that this is what most middle-class are in to? 😉 tia, cal.

  3. CC AKA ‘Carbon Copy’ ‘CopyCat’
    I met this cat at UC Davis when she was just a kitten.
    I remember how strongly I felt about this issue and still do.
    There are some things in this life that we just have to accept and death is one of them. The other is that not one of us is the same, animals included. We are all unique and that is the beauty in this life. It makes us appreciate one another. If we become disposable because we can just create a new one, whats to appreciate then?

    • Good point. Death is part of life and we should accept it, as you say. To be honest, I do not think people want a cloned version of their cat. Even if the cloning was perfect. This is because we are programmed to accept keeping a cat for a certain period of time and we are programmed to accept the death of a companion. We are aware of these time limits. Cloning totally upsets these natural rhythms.

      Cloning of livestock for a utilitarian reason would be entirely different and more acceptable but in my opinion it is still unacceptable because I believe in accepting nature as it is.

      • Michael do you mean cloning livestock for meat eaters? I wonder if they would eat cloned animals? I can’t look objectively at this because I’m vegetarian but didn’t someone recently grow some ‘meat’ in a lab? So that living feeling animals didn’t have to be born to be killed any more(sometimes their life a living hell and their death horrific)
        I hate the words livestock and food animals, it makes them sound like they are different to other living breathing feeling animals, when they are not, they want to live, they want to enjoy their life, they don’t want to be born to die prematurely and be eaten.
        Would any meat eating animal lovers here eat ‘meat’ grown in a lab?
        I’m not getting at meat eaters, I was one myself for a long time, I’m just interested to know how others feel about this?

  4. Jennifer, this is where you lose me,

    If we become disposable because we can just create a new one, whats to appreciate then?

    The premise that you pose, “we become disposable?” “we become disposable.” …?

    Could we discuss this here on PoC, Michael? 😉 -cal

    • Yes, we can discuss disposability of animals on this website, if you want to. I think there is a link between cloning and the disposable nature of domestic animals within certain sections of the community. It is about consumerism is not it? And treating a companion animal as a consumer product. Cloning is like manufacturing and manufacturing relates to inanimate objects which is almost the way that some people treat the domestic cat, sometimes.

  5. The last time I checked, cloned animals are immune to common and chronic diseases. This is really new and very interesting. Maybe cloned pets who still suffer diseases are not that perfectly cloned beings.

    • Thank you for suggesting that. I had not heard that cloned animals were immune to common chronic diseases. My first reaction is that it is incorrect but I will certainly check it out.

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