Hereditary health and genetic diversity within the Chihuahua dog breed

Hereditary health and genetic diversity within the Chihuahua dog breed

Health & Safety

The Chihuahua is the smallest of all of the recognised dog breeds, and also one of the most popular among people that love toy dogs and lap dogs! Dogs of the breed stand between 6-10” tall at the withers, and can weigh between 4-6lb, making them smaller than some of the larger breeds of cat, but still, all dog! They can be either long haired or short haired and come in a reasonably wide range of colours, and are instantly distinctive thanks to their shape and build, as well as their diminutive size!

While it might seem at first as if owning a tiny dog should be much easier and less challenging than owning a large dog, this is certainly not the case, and anyone who is considering buying a Chihuahua is advised to spend plenty of time researching the core traits and temperament of the breed prior to making a purchase. As well as the temperament and care needs of the Chihuahua, it is also important to find out as much as possible about the health of the breed as a whole, what their lifespan is likely to be, and if the breed is known to suffer from any hereditary health problems. In this article, we will look at the hereditary health and genetic diversity of the Chihuahua in more detail. Read on to learn more.

Chihuahua longevity

The average lifespan of the Chihuahua is very variable, with statistics gathered from owner surveys finding the average to be between 12-20 years. 12 years is bang in the middle of the average for dogs of a similar size, but of course 20 years indicates a significantly long life, and is a figure that very few dogs can hope to achieve. Starting off with a healthy puppy that does not come from a breed line known to suffer from significant health problems is the best way to ensure a long life, but equally important is feeding a correct diet, keeping the dog fit and active, and ensuring that regular preventative veterinary appointments are not overlooked.

Genetic diversity within the Chihuahua breed

The coefficient of inbreeding statistic for the longhaired Chihuahua is 4%, while for the shorthaired variant it is 5.8%. This is relatively low for purebred dogs, with under 6.25% being considered as ideal. The significant number of Chihuahua’s worldwide as well as within the UK means that there is a lot of genetic diversity across the breed, and that inbreeding is not a significant problem within the breed.

Conformation issues

The small, delicate build of the Chihuahua causes some potential problems and vulnerabilities across the breed that all owners should be aware of. These include:

  • The potential for hydrocephalus (fluid on the brain) due to the shape and size of the head.
  • Fragile bones, due to the dog’s petite build.
  • A heightened propensity to deafness in merle-coloured Chihuahuas, to the extent that The Kennel Club refuses to register puppies that have a merle parent.

Health testing for Chihuahuas

Various health tests can be performed on the Chihuahua to identify the presence of or predisposition to certain hereditary health problems. These include:

  • Testing for Chiari malformation and syringomyelia, which causes fluid pockets to develop along the spinal cord, causing ongoing and severe pain.
  • DNA testing for the merle gene, which can cause deafness, is also possible.
  • DNA testing can also identify a deficiency of a key enzyme necessary for healthy red blood cells, known as pyruvate kinase deficiency.

Other health issues across the breed

The Chihuahua breed as a whole has been identified to have an elevated predisposition to a relatively wide range of other potential problems too, but for which no pre-breeding test is currently available. These include:

  • Urinary stones, or urolithiasis.
  • Problems delivering live young normally, which may require veterinary intervention.
  • Narcolepsy, or sudden collapse into sleep with no warning.
  • Legg-Calve-Perthes disease, which affects the femur bone and leads to problems moving normally, as well as pain.
  • Blood clotting disorders such as haemophilia, particularly within male dogs of the breed.
  • Problems with the kneecaps, such as patellar luxation.
  • Mitral valve degeneration, or myxomatous, plus narrowing of the pulmonary valve of the heart, both of which are serious cardiac conditions.
  • Allergenic atopy, which is a hypersensitivity to certain types of protein particles, including pollen. This can lead to severe skin allergies, which cause intense itching, and may cause scarring and infections of the skin.
  • Tracheal weakness, when the cartilage of the trachea does not form properly, leading to tracheal collapse and problems breathing.
  • Skin melanomas, a type of cancer.
  • Problems with the teeth and jaws, including an overcrowded mouth and the failure to lose baby teeth in the normal manner.
  • Water on the brain, or hydrocephalus.
  • Cervical spine instability, leading to problems with the spine and neck, which are often painful.
  • Eye diseases, including corneal dystrophy.
  • An autoimmune disease called myasthenia gravis, which is a neuromuscular condition leading to progressive weakness.
  • Various other autoimmune conditions, including necrotising leucoencephalitis, causing inflammation of the brain and premature death.


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