Merle Statement

Genmark Merle Genetic Testing

http://www.genmarkag.com/canine_faqs.php

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.

Genetic Testing for the Merle Gene

With the recent discovery of the merle gene, a genetic test is now available that allows for the identification of the merle allele. This technology is patent pending ( U.S. Serial # 60/708,589) and available exclusively thru GenMARK, the DNA technology service of VITA-TECH Laboratories LLC. By testing dogs for this genetic trait, it is possible to:

* allow identification of merle dogs to prevent undesirable merle to merle breeding

* classify harlequin Danes as single or double merle

* identify cryptic merles

If you have any questions, please contact us at:
Email: customerservice@GenMARKag.com
Phone: 877-766-3446
Fax: 608-310-9512

The Merle Color Pattern, Chihuahuas, and the CCA

The AKC's definition of "merle": A color pattern involving a dominant gene (the M or Merling Series) and characterized by dark blotches against a lighter background of the same pigment, e.g., blue merle in Collies and red "dapple" in Dachshunds.

The merle color pattern and Chihuahuas is a serious concern for the Chihuahua Club of America. The Officers and Board of the CCA believe any factor that might affect the health of Chihuahuas deserves much consideration and study. To that end, both the Board and a Board-appointed committee of CCA members studied merle information from numerous knowledgeable sources.

Data was collected from, but was not limited to: current scientists who are researching coat color heredity and its link to possible health problems; the published works of respected scientists regarding coat color genetics; other breeds' parent club designees who provide information on the matter; and the web sites of breeds who have had long-term experience with the merle pattern and the health problems that may accompany it.

CCA discovered that, although some may refer to the merle color pattern as "lethal", scientists and geneticists generally do not. We did find terms such as "serious" and "sub-lethal" when the possible problems of deafness, blindness, and sterility were described.

Sheila Schmutz, a current respected researcher and source for scientific information, wrote the Chihuahua Club of America advising against changing the breed's standard for the sole purpose of disqualifying the merle color pattern. Information about dog coat color and color patterns can be found at http://homepage.usask.ca/~schmutz/dogcolors.html

The CCA surveyed its membership on the matter and learned that some long-time breeders had seen the pattern for many years. Since the breed's recognition by AKC in 1904, the American standard for the Chihuahua has permitted, "Any color - solid, marked or splashed".

As translated and published in the April-May 2005 issue of "LOS CHIHUAHUAS" p.17-23, the recently revised Mexican standard for Chihuahuas reads, "All colours in all possible shades and combinations are admitted."

The Chihuahua Club of America recognizes that, as with other health or conformation considerations, recommended breeding practices may have little effect on breeders who are not interested in the CCA, the AKC, or in breeding to the standard. However, the Chihuahua Club of America's Constitution, ARTICLE I, section 2(a),(d), and (f), requires the Club and its members "to encourage and promote quality in the breeding of pure-bred Chihuahuas; to do all possible to bring their natural qualities to perfection; to do all in its power to protect and advance the interests of the breed; and to promote the qualities of the Chihuahua breed to the members and general public through publications, educational seminars, library data bank, etc."

Scientific research indicates that some of the health problems associated with, or attributed to, the merle color pattern may also occur with the color white and/or with other color patterns or color combinations. The merle issue is not a simple one, especially in the Chihuahua, because, since its arrival in the United States, all colors and markings have been and are permissible. Chihuahuas with the merle color pattern are part of the Chihuahua gene pool.

Hearing, vision, and other health related tests/screenings provide important information for breeding decisions. Based upon material the CCA received from parent clubs of other "merle familiar" breeds, those clubs have reached the same conclusion. One requirement for membership in some breeds' parent clubs is that the individual tests all breeding dogs for specific health problems prior to their being bred.

The Chihuahua Club of America suggests that breeders review the parent club web sites for Australian Shepherds, Cardigan Welsh Corgis, Collies, Dachshunds, and Shetland Sheepdogs. Most contain information relating to merle patterning and breeding considerations.

A few "merle familiar" breeds provide some cautionary breeding practices: merles should not be bred to merles; white pigment, especially in the ears, may indicate a hearing problem; some merle patterns are difficult to discern when the dog is young and some fade away with age. Most recommend testing for hearing, vision, and other inheritable problems before breeding takes place. Many of these tests are recommended without regard to color.

It is EXTREMELY important for Chihuahua breeders to specify the merle color pattern on AKC registrations. The AKC has approved the Chihuahua Club of America's request to add "merle" to our color/markings registerable "list".

The AKC also approved the CCA's request that owners be permitted to make a one-time color/marking change for previously registered merle Chihuahuas that were not registered as such. The AKC directions for making the color/marking designation change are on this web site.

1. It is most important that the color/markings/patterns of Chihuahuas be registered accurately.

2. It is possible that serious health problems (deafness, blindness, sterility, etc.) may result if merle patterned dogs are bred to each other.

3. Testing/screening for heart, vision, hearing, patella, and other possible health problems is valuable for Chihuahuas.