Rat TerrierArticles, research links, merle gene in dogs, dog blindness, dog deafness

*Do you have the time to meet the demanding needs of a puppy/dog (feeding, training, and exercise)?

*Are there children or elderly in your family, if yes, will this be the right dog for your family?

*How many hours a day are you away from home (working, recreation, etc...), will your puppy be kenneled during this time?

*Primary Lens Luxation aka PLL: is an eye problem in many of the Terrier breeds as well as Rat Terrier. "The lens of the eye normally lies immediately behind the iris and the pupil, and is suspended in place by a series of fibers, called zonular ligaments. It functions to focus light rays on the retina, in the back of the eye. When partial or complete breakdown of the zonular ligaments occurs, the lens may become partially dislocated (Lens Subluxation) or fully dislocated (Lens Luxation) from the lens’ normal position. Movement of the lens forward through the pupil into the Anterior Chamber of the eye is termed Anterior Lens Luxation. Movement of the lens backwards into the Vitreous Chamber of the eye is termed Posterior Lens Luxation." http://www.caninegeneticdiseases.net/GLX/basicLUX.htm

Rat Terrier History, Thank you to AKC for providing this information!

"The Rat Terrier is an American breed that originated from a mixture of crosses by early immigrants of this country using old time Fox Terriers and other European Terriers common in the 19th century; the Old English White Terrier, Manchester Terrier, Bull Terrier, etc., and later crossed with Beagles, more Smooth Fox Terrier, Toy Fox Terriers, Whippets, Italian Greyhounds and other available Feist breeds.

During the 1910s and 1920s, the Rat Terrier was one of the most common farm dogs. Because Kansas Jack Rabbits were plaguing crops in the Midwest, to increase the speed and versatility of the Rat Terrier, some Farmers began breeding them to Whippets, Italian Greyhounds and other "snap dog" breeds. Around the same time, others in the Central and Southern regions, bred their Rat Terriers to Beagles to bring out a stronger prey and pack drive for hunting purposes. These early crosses eventually gave the breed the speed and "nose," as well as the good disposition they are known for today."

The different dog breeds used to make Today's Rat Terriers are: Information provided from AKC website, unless otherwise noted.

Old English White Terrier - (invented and embraced in the early 1860s by a handful of breeders anxious to create a new breed from a prick-eared version of the small white working terriers that were later developed into the Fox Terrier, the Jack Russell Terrier, the Sealyham Terrier and later in America – the Rat Terrier.) information provided from wikipedia, this site is not a scholarly accepted reference.

Manchester Terrier - (dogs used to make this breed are: Whippet and Un-named Terrier type)

Beagles - (Previous to 1870 in the United States, the little hunting hounds of the southern states, then called Beagles, were more of the type of straight-legged Bassets or Dachshunds with weaker heads than the Bassets.) The beagle history is pretty interesting and can be found here http://www.akc.org/breeds/beagle/history.cfm

Smooth Fox Terrier - (The important ancestors of the Smooth are believed to include the smooth-coated black-and-tan terrier, the Bull Terrier, the Greyhound, and the Beagle.)

Toy Fox Terrier - (small Smooth Fox Terriers were crossed with various toy breeds including Miniature Pinschers, Italian Greyhounds, Chihuahuas and Manchester Terriers. The resulting dog – the Toy Fox Terrier –" www.akc.org)

AKC states "any other available Feist or Snap breeds" - The Feist - "believed that the feist was descended from Native American dogs, mixed with small terriers from Britain." More information on feist can be found here http://www.answers.com/topic/feist , "There has been considerable crossing of feist dogs, since they are bred primarily for performance as hunting dogs. Feist dogs are the progenitor of what we now call the Rat Terrier. The Rat Terrier is a specific breed within the "feist" umbrella. Because the word "feist" refers to a general type of dog just as "hound" and "terrier" refer to a group of breeds, Rat Terriers are often called "feist". The terriers brought to America in the 1890s from England were crossed with feist dogs already here in addition to some of the Toy breeds (Toy Fox Terrier, Manchester Terrier and Chihuahua) to develop the Rat Terrier we know today."

The Rat Terrier is a man created breed and there are many sizes, and colors/patterns available within this dog breed which is what makes them so desirable.

AKC: "the sire and dam of a dog are members of a recognized breed and that the ancestry of a dog consists of the same breed over many generations". (all of Mini Distractions Rat Terriers have years of recorded Pedigree information.)

Merle Rat Terriers

There is such thing as a Merle Rat Terrier (if their pedigree matches what the AKC purebred description is then they are purebred), and they are becoming more and more popular! The merle color pattern is beautiful and just as purebred as any other rat terrier color/pattern. There are several rat terrier breeders in the U.S. that are stating that the merle color/pattern in the rat terrier means that the dog isn't a purebred (these breeders are stating this for their own personal gain and not for the rat terrier breeds best interest). This is information that is NOT FACTUALLY SUPPORTED, and so please do your own research and you will see that the Original Breeds that were used to Create the Rat Terrier had merle colors/patterns in them and this IS where it came from. The Rat Terrier is a man created breed and there are many sizes, and colors/patterns available within this dog breed which is what makes them so desirable.

Articles: (pay close attention: Health issues can happen in any breed, and any color but in the case of merle's it happens when Merle's are bred to Merles!) Reputable breeders know this and only breed a merle to a non merle to alleviate this health concern.

Merle Strain Article
George M. Strain, PhD

"Recent issues of Top Notch Toys have printed dialog about the merle gene,... . One particular article (1) cited research of mine (2) with an incorrect interpretation that I wish to correct. In addition, I would like to provide unbiased up-to-date information on the merle gene that may inform and clarify the debate on this issue. I have been performing research on hearing and deafness since the late 1980's, and am identified as a leading authority on deafness in dogs, so I am well positioned to provide this information. I should point out that publications and writings of mine from past years discussing the merle gene no longer represent my opinion, as recent research has led me to change my position.

The above cited article contained the statement that According to Dr. George Strain merle and piebald dogs with blue eyes are 50% more likely to be deaf.@ The research from which this was drawn only applied to the piebald gene and only applied to the Dalmatian breed, where blue eyes and deafness are a wide-spread problem (30% of US Dalmatians are deaf in one or both ears). My research did not apply to dogs with merle, and I am unawa re of any study examining this issue using adequate numbers of dogs and dogs from breeds other than Dachshund, where the published studies have limitations (see below).

Two pigment genes are associated with deafness in dogs: piebald (s) and merle (M). Piebald, which is present in Dalmatians, bull terriers, cocker spaniels, Jack Russell terriers, Chihuahuas and others (RAT TERRIERS), is a recessive gene. There are three recessive alleles for piebald: Irish spotting (si), piebald (sp), and extreme white piebald (sw); dogs that have uniform color without white carry the dominant allele (S). The piebald gene produces areas of white by suppressing pigmentation cells (melanocytes). Merle, which is present in Shetland sheepdogs, Australian shepherds, Dachshunds, Great Danes and others, is a dominant gene. Merle produces a color pattern where patches of color are diluted or absent (white); animals homozygous with the recessive allele (mm) have solid color. Dogs with piebald must be homozygous to have areas of white, while merles can be either heterozygous (mM) or homozygous (MM). There is no evidence to suggest that dogs carrying both the piebald and merle genes have an increased likelihood of deafness.

Much of the literature on merle in the past focused on problems seen in homozygous merles and in breeds where the merle gene can produce dramatic effects B in some cases including deafness, blindness and microphthalmia, and sterility. Even heterozygous dogs in these breeds can have less serious visual and auditory deficits. This indeed happens with some breeds, but unfortunately many people have taken this truth and extrapolated it to apply to all breeds carrying the merle gene, which is not true. For example, dogs in the Catahoula breed can be homozygous merle without any of these health defects, and heterozygotes do not seem to be affected. Until recently it was not possible to even distinguish between mM and MM merles in some breeds.

Since not all breeds carrying the merle gene experience the deleterious effects, it is incautious to proclaim that the presence of this pattern in a breed will be injurious to the breed without first investigating whether deaf or blind dogs result from breeding heterozygous merles. Are there any known deaf or blind merle chihuahuas? If so, are they heterozygous or homozygous? In many breeds carrying merle, breeders know not to breed homozygous merles, and visual and auditory deficits do not seem to be a problem in the heterozygotes. Studies have examined auditory function (3) and visual function (4) in heterozygous and homozygous dappled (merle) Dachshunds, as described in several writings by Dr. Malcolm Willis. These studies, from geographically and numerically restricted populations, found hearing loss and deafness and visual abnormalities, but only examined small numbers of dogs B 38 in the first study and 18 in the second. Dappled Dachshunds, when carefully bred to avoid MM, do not appear to have deafness or blindness in the general population, so one must be careful to not raise alarms at the presence of merle in a breed until experience shows that a true problem exists.

A large leap in understanding merle occurred when Clark and Murphy of Texas A&M University identified and sequenced the canine gene for merle in 2006 (5). The gene, named SILV, (also known as Silver in mice) plays a role in pigmentation in skin, eye, and ear. Dogs with the merle phenotype have a short piece of DNA inserted into this gene B a DNA modification known as a short interspersed element (SINE). This work was performed with Shetland sheepdogs, then confirmed in merles from eleven other breeds, including chihuahua. The sequence of the SINE was the same in all breeds, suggesting that all breeds in the study shared a common ancestor. The merle SINE insertion has three components: a head, a body and a tail; the latter contains a long string of repeated adenine nucleotides (polyA). For a dog to show the merle phenotype, it must have both the SINE insertion and a polyA tail that is of sufficient length (90-100 adenine repeats). Some merle-merle breedings produce homozygous merles called cryptic because they don=t show the merle phenotype, and when bred they do not produce any merle offspring. It turns out that the polyA tail in cryptic merles has been truncated to 65 or fewer adenine repeats. So, the merle gene phenotype can revert to the non-merle in one generation. In the same way, it is theoretically possible for the polyA tail length to increase from genetic processing error, spontaneously producing a merle (5,6). The likelihood of this possibility is unknown but probably low.

It has been suggested that merle appeared in the Chihuahua breed from a cross to another breed, such as the Dachshund. Others have suggested that the gene has been present for many generations, but that the pigmentation pattern was incorrectly described, such as blue and tan or black and silver. A single event of the first possibility might still make it hard to explain all of the merle Chihuahuas now in existence. Regardless of the source of merle in the breed, to my knowledge there is no data at this time to suggest that merle Chihuahuas are prone to visual or auditory problems. I would encourage the breed organization investigate the prevalence of visual and auditory disorders in merle Chihuahuas prior to making decisions affecting the breed standard."

More information on deafness in general can be found on my research web page: Deafness in Dogs and Cats, www.lsu.edu/deafness/deaf.htm.

1. Lambert G. 2006. Chihuahuas - Any color (breed) marked or splashed?? Top Notch Toys 22(4):116.
2. Strain GM. 2004. Deafness prevalence and pigmentation and gender associations in dog breeds at risk. The Veterinary Journal 167(1):23-32.
3. Reet z, I., Stecker, M., & Wegner, W. 1977. Audiometrische Befunde in einer Merlezucht [Audiometric findings in dachshunds (merle gene carriers)]. Deutsche Tierärztliche Wochenschrift 84(7):273 277.
4. Klinckmann G, Koniszewski G, Wegner W. 1986. Light microscopic investigations on the retinae of dogs carrying the Merle factor. Journal of Veterinary Medicine A 33(9):674 688.
5. Clark LE et al. 2006. Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog. Proceedings of the National Academy of Sciences 103(5):1376 81.
6. Cordaux R, Batzer MA. 2006. Teaching an old dog new tricks: SINEs of canine genomic diversity. Proceedings of the National Academy of Sciences 103(5):1157 8.

"The second white pattern is commonly seen in Beagles (and other hounds), Bulldogs, Cocker Spaniels and English Setters (and other breeds as well). It is called the Piebald Spotting Gene (S^p - non-symmetrical random white pattern). This pattern does not always cause deafness, it is only a problem when the inner ear is missing pigment (see "What Causes Deafness in Dogs?" above).

Dalmatians, Boxers, Bull Terriers, Great Pyrenees, and possibly Mantle/Boston Great Danes (this is not known for certain) are examples of the Extreme White Spotting (or Extreme Piebald) Gene (S^w). When the other half of the gene pair is a solid, the dog will have a white blaze, collar, and white legs (known as "flashy" in Boxers). If two dogs with this pattern are bred, 25% of the pups will be almost all white (known as "pattern white," or "color headed white"). Sometimes these dogs will be deaf, and sometimes not, depending on where the pigment ends up. Dalmatians are homozygous for this gene (carry 2 copies), with the spots in the coat being caused by the ticking gene (which can combine with any of the other white trims as well).

So there are many ways for a dog to have more white in its coat than it should. Sometimes it is just a guess as to why a dog has the pattern that it does, and there is still a lot of research being done in this area. Since owning an unilaterally deaf excessive white bitch (CRK's MISS PIGGY) bred down from a pied x merle. I have done a lot of research on merle, pied and white genes. The main reason I used a unilateral deaf dog with excellent conform, temperament and working drives in my program, is the fact that that excessive white and deafness is NOT hereditary but caused by a Merle (Mm) x Pied (Sp), Merle (Mm) x Merle (Mm) or Merle (Mm) x Excessive White (Sw) . But remember unlike double Merle, excessive whites are not only restricted to Merle(Mm) x Merle(Mm) but also Merle(Mm) to White(Sw) or Merle(Mm) to Pied (Sp).. But if you breed to 100% Black or 80% Black to 20% white like (SPOOK) to a hard of hearing, excessive white dog like (MISS PIGGY) . Then you will get 100% merle pups that WILL all have good hearing."

"Deafness is not just restricted to breeds that have Merle's but is seen in breeds that produce majority white phenotype with little or no pigment like the Dal or EBT."

rat terrier health, primary lens luxation. Rat terrier health problems. rat terrier health issues. Training rat terriers. Hunting with rat terriers. Rat Terrier history. Rat Terrier registries. Genetic Diseases in Rat Terriers. Buying a new rat terrier puppy. UKCI registry. CKC registry. AKC registry.