Animalia Life

The Breed History
Since the 1500s these unusual dogs have been reported, and are thought to have originated in Mexico. Their history perhaps goes back to ancient societies such as the Aztecs since dog skulls have been found that resemble this breed's in size and shape that date to 3300 years ago in Central America. The name derives from the Aztec word for God "Xoloti" and "Itzcuintli", the Aztec word for dog. Commonly, these dogs are referred to as the Mexican Hairless. AKC recognition occurred in 2011. Molecular genetic (mitochondrial DNA) results do not support a New World domestication of Xoloitzcuintli, or close association with other hairless breeds of dogs. Despite their phenotypic uniformity, the Xoloitzcuintli has a surprisingly high level of mtDNA sequence variation, suggesting that the breed was founded with a large number of dogs from outbred populations.

Breeding for Function
Throughout their history, their prime purpose has been companionship; perhaps they were also the object of sacrifice in ancient Aztec, Toltec and Mayan civilizations. They were thought to have healing powers because of their warm skin temperature and were used by arthritis sufferers for that purpose.

Physical Characteristics
Toy
Height at Withers: 11-12" (28-31cm),
Weight: 9-18 lb (4-8 kg)
Miniature
Height at Withers: 12-15" (30-38 cm).
Weight: 13-22 lb (6-10kg)
Standard
Height at Withers: 16-22.5" (41-57 cm)
Weight: 20-31 lb (9-14 kg)
Coat: There are two haircoat types: Hairless and Powder Puff. The latter is not accepted for show purposes. Colors include orange, black, slate, liver, bronze, and charcoal.
Longevity: 12-15 years
Points of Conformation: This is a small finely put together dog with a noble carriage, and similar to sight hounds in body structure. Limbs are straight boned. The somewhat almond-shaped eyes are wide set, dark brown, and moderate in size and depth of setting. The muzzle tapers to a point, nose is black, ears are erect and triangular with pointed tips, and sometimes traces of hair exist on the top of the skull, on the tip of the tail and around the toes in the hairless type. They have a moderately deep thorax, and the abdomen is well tucked up. The fine tail hangs down and tapers to a point at the tarsus. The long neck is slightly arched and finely built, and the feet are hare-like in conformation. Their gait is quick and elastic.

Recognized Behavior Issues and Traits
Reported breed characteristics include: Active, a good alarm barker and good in apartments. Only suitable as an indoor dog, and needs a winter sweater unless in a sub-tropical or tropical environment. The personality is similar to the terriers-like fox terriers particularly; also quite playful. It may be necessary to bathe a Xolo periodically and apply lotion to keep the skin moist. This is a type of dog that has low exercise needs. Xolo dogs are good with children, but children need to be very gentle so as not to injure these dogs, especially the smallest variety. Good for some allergy sufferers (hairless variety).

Normal Physiologic Variations
Hairlessness is caused by a autosomal semidominant mutation in the FOX13 gene that is lethal in utero in the homozygous state. This gene also produces variably expressed missing premolars in the heterozygous state. Because of the lethal homozygous state, breeding two heterozygous hairless dogs together produces a 2:1 ratio of hairless to (homozygous normal) powderpuff dogs. Breeding hairless to powderpuff dogs, produces a 1:1 ratio of hairless to powderpuff offspring. Xoloitzcuintli are very sensitive to heat and cold. The skin is thin, and prone to lacerations, and dryness. They sweat through their skin so they do not pant as much as other breeds. Hairlessness is accompanied by early atrophy of the thymus after birth, and is followed by poor accumulation of lymphocytes in the thymus-dependent area of the spleen and the mesenteric lymph nodes. This presentation is different from that seen in athymic nude mice and rats. No immunodeficiency or diminished antibody response has been documented in the breed.

Drug Sensitivities
None Reported

Inherited Disease
Incomplete Dentition: It is common to have variable expression of missing premolars with the autosomal dominant hairless phenotype.
Patella Luxation: Polygenically inherited laxity of patellar ligaments, causing luxation, lameness, and later degenerative joint disease. Treat surgically if causing clinical signs. Too few Xoloitzcuintli have been evaluated by the OFA to determine an accurate frequency in the breed.
Hip Dysplasia and Legg-Calve-Perthes Disease: Polygenically inherited traits causing degenerative hip joint disease and arthritis. Too few Xoloitzcuintli have been screened by the OFA to determine an accurate frequency in the breed.
Elbow Dysplasia: Polygenically inherited trait causing elbow arthritis. Too few Xoloitzcuintli have been screened by the OFA to determine an accurate frequency in the breed.

Disease Predispositions
Sunburn: Xoloitzcuintli are very sensitive to sunlight (ultraviolet radiation). Sun block should be used when exposed to direct sunlight.
Comedomes (Blackheads): The skin of Xoloitzcuintli is prone to spontaneous comedome formation throughout the dorsal skin, on the limbs and prepuce. Plugged follicles containing abundant sebum and keratic substances resembles human acne.
Cryptorchidism: Unilateral or bilateral retained testes reported in the breed. This is a sex-limited disorder with an unknown mode of inheritance.
Hypothyroidism: Inherited autoimmune thyroiditis. Too few Xoloitzcuintli have been tested at Michigan State University to determine an accurate breed frequency. (Ave. for all breeds is 7.5%).
Lawn Chemical Hypersensitivity: Reaction to lawn chemicals included epidermal degeneration, vasodilation, intradermal infiltration of inflammatory cells, and comedoes with well-developed pilosebaceous glands.
Inherited Ocular Disorders: Too few Xoloitzcuintli have been CERF examined by veterinary ophthalmologists to determine an accurate frequency of inherited ocular disorders.

Isolated Case Studies
None Reported

Genetic Tests
Tests of Genotype: None
Tests of Phenotype: Recommend hip and elbow radiographs, patella evaluation, CERF eye examination, thyroid profile including autoantibodies, cardiac examination, and examination for descended testes.

Miscellaneous
- Breed name synonyms: Mexican Hairless, Tepeizeuintli, Xolo
- Registries: UKC, CKC, KCGB (Kennel Club of Great Britain), AKC -provisional, NKC
AKC rank: (None) Became an AKC recognized breed Jan. 2011. Entire studbook registered.
- Internet resources: Xoloitzcuintli Club of America: www.xoloitzcuintliclubofamerica.com
Xoloitzcuintli Club USA: www.xoloworld.com