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Merle Chihuahuas

    Due to the increasing popularity of this color pattern, I feel that I need to add some information about Merle Chihuahuas, including the potential health problems, on my website. Many people interested in purchasing a Merle Chihuahua, may be unaware of the problems that they might have with their new pet.

Hopefully, with more knowledge about this pattern, breeders will reconsider breeding this color pattern.

To control the pattern in the breed, these countries (and/or kennel clubs) so far have taken action:

Australia (banned registration of merles)
New Zealand (banned registration of merles)
Canada (Merle is now a Disqualifying Fault (DQ) in the Chihuahua standard)
Great Britain (Merle is now a Disqualifying Fault (DQ) in the Chihuahua standard and merles are also banned)
Germany (Merles can not be shown/bred)

Updated July 27, 2009
ALL FCI countries (83 countries) have now made merle Chihuahuas a Disqualifying Fault (DQ), and in several countries, this means puppies from merle parent(s) can not be registered.
See full list of applicable member countries here: http://www.fci.be/membres.aspx

Updated June 24, 2010
Merles are NO LONGER registerable in Canada, whether it be puppies that come from a merle parent, or merles that are imported from other countries.
See information link here: http://www.ckc.ca/en/Default.aspx?tabid=201&NewsID=375&prevID=202

   Merles are the newest style to hit Chihuahuas. The coat pattern has only shown up in the breed in the past 15 years or so. There is NO mention of this color what-so-ever in any Chihuahua breed book, or genetics book that lists certain color patterns that are in the Chihuahua breed. This coat pattern has also appeared simultaneously in several other breeds as well (these include Poodles, Cocker Spaniels, APBT, and Miniature Pinchers). Merles can come in a variety of color patterns, including red merle and blue merle (above). They can also have what is called a hidden or cryptic merle, where the merle pattern does not show up, such as on a light colored dog, or where the merle pattern does not cover a large area of the dog (sometimes only one hair will actually be merle patterned).

The Merle gene itself is a dominant trait, which means one of the parents MUST be a Merle for the gene to be expressed (or show up) in a puppy. This is not the type of gene that remains hidden for many generations like a recessive gene. Since Merles were never heard of more then 15 years ago, this color pattern has probably resulted from cross-breeding other breeds of dogs that have merles such as a Dachshund, to the Chihuahua and falsifying the purebred dog registration. While the Merle color can come up from genetic mutations, this is most likely not the case as it is the same gene that is also present in Aussies, Dachshunds, Shelties, etc.

 Ultimately, if you buy a Merle Chihuahua, you are probably not getting a purebred Chihuahua, just a mixed breed (even though it might actually have registration papers). Also, a large majority of Merle Chihuahuas are consistently very big, in the 6 to 10 lb range, which is very unlike a purebred Chihuahua and is probably a result from a throw-back to the mixed breed dog that was introduced years ago to get the Merle Chihuahua.

What the Merle Breeders do NOT tell You

    Another much more serious and important issue is the higher occurrence of health problems in Merle Chihuahuas. You may wonder how this is so, when merle is only a color pattern? Well, unfortunately, unlike other colors, the merle gene acts on a color and lightens and whitens certain parts of it (creating patches)...the whitening is what causes defects. Often, when a dog's coat is whitened, the pigment inside of their ear and on their eye, also whitens...making the dog DEAF and BLIND as the nerves endings atrophy and die.

As quoted from Idexx, makers if the merle genetic blood test (http://www.idexx.ca/diseasesinseason_profile.cfm?CFID=16946&CFTOKEN=66320611):

"Health Problems Associated with the Merle Allele - Both heterozygous merle (Mm) and homozygous double merle (MM) dogs may exhibit auditory and ophthalmic abnormalities including mild to severe deafness, increased intra ocular pressure, ametropia, microphthalmia and colobomas. The double merle genotype may also be associated with abnormalities of skeletal, cardiac and reproductive systems."

Definition of Heterozygous-one parent is a merle, the other is a non-merle. Also known as single merles, or Mm.
Definition of Homozygous-both parents are merle. Also known as double merles, or MM.

Based on information about the merle gene in Dachshunds, all merles that are brought into the world have a 36.8% chance of developing some sort of hearing loss, resulting from either slight hardness of hearing to total deafness (Willis). This percent is for puppies that result from one parent that is a merle, and the other that is a non-merle. Other problems such as eye problems were also apparent. While many breeder's admit that there are problems when breeding two merles together, they do not admit there is also a problem when breeding a merle to a non-merle which is the breeding most breeders do. This is what the Merle Chihuahua breeders DO NOT tell you. You can still get deaf and blind puppies from this type of "safe" breeding. So please keep in mind, if you are interested in getting a Merle Chihuahua, you may not actually get a healthy puppy. A pup may appear to be healthy, but might actually have impaired hearing or vision. For the reason of health problems and questionable parentage, the presence of the merle pattern in Chihuahuas is being banned in many countries world-wide. For more information on this study by Dr. Willis, and for his viewpoint of the merle pattern in Chihuahuas, please go here:


    This is one breeder's experience of breeding Merle Chihuahuas. She encountered all of these problems within 18 months of breeding Merles and the heartache of the problems she experienced was too much for her, so she no longer breeds merles. The blind and deaf Merle puppies on her site were a result of single merle breedings (one parent was a merle and the other wasn't), showing you can still get problems even if you don't breed Merle to Merle. Click on the link below:

Click here: A Breeder's Experience

Please be advised that if you are still interested in getting a merle, that you could end up with a dog that has deafness or hearing issues, not to mention a questionable pedigree and usually a "big" Chihuahua.

(pictures used with permission)

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