The merle gene and its effects
As extraordinary as they may look we see some breeders promoting the Merle Chihuahuas as extremely rare and unique and to be honest this is exactly how we want to keep them.
What they don't understand is although most people like the unusual display of colors associated in the Chihuahuas coat and eyes they are in fact a mutation of a specific band of genes which affects sight and hearing and also dilutes coat colors.
The genes that have been identified in a 2006 study showed that they are inherited from mother or father or both so being passed on to their puppies who then can show different levels of severity of the genes. The science being the Merle gene will leave people scratching their heads but simply put there are single Merle traits and double Merle traits with the double being the more serious and giving these problems:
Increased Intraocular pressure : excessive pressure created in the eye.
Ametropia : vision impairment due to a refractive error such that images fail to focus upon the retina.
Microphthalmia : a smaller than normal eye due to a defect occurring early in development. Affected dogs may have prominent third eyelids. Other eye defects are common in animals with this condition, including defects of the cornea, anterior chamber, lens and retina.
Coloboma – a defect in ocular tissue; a cleft or missing portion of components of the eye, most commonly affecting the iris.
Put into plain English this ultimately means deafness and blindness at some stage of their life.
Now although there is no mention of the colors or coat patterns in the above problems these are not health problems but an indication of the presence of the Merle Gene. Breeders who promote the Merle Chihuahua Puppies we feel are not showing enough responsibility for the breed by trying to eradicate the mutant genes within their breeding stock. There is a test available although it is in Canada which can identify within the dogs DNA the rogue genes so responsibility lies with the breeder to have their dogs DNA tested for Merle if they are producing Merle offspring therefore identifying the dogs not to breed from. Greedy breeders will not stop breeding these as money is more important than the Chihuahuas health.
Doggy science can be a touchy subject with many different views but at the end of the day health within the breed needs to over shadowed by customers preferences.