Adult Onset Neuropathy (AON) in Cocker Spaniels: A Complete Guide

Adult Onset Neuropathy (AON) is a serious hereditary neurological disorder affecting mainly English Cocker Spaniels, usually appearing when the dog is middle-aged or older. Because symptoms often emerge between seven and nine years, many affected dogs may have already been bred unknowingly.

Thankfully, in the UK, a DNA health testing scheme supports breeders and potential puppy buyers in determining the genetic status of their dogs, helping to make informed choices to reduce the risk of passing on this condition.

AON causes progressive weakness first in the hind limbs and later in the front limbs, along with difficulties in coordination, movement, and even swallowing. These challenges can severely affect a dog’s quality of life.

This comprehensive guide explores the nature of adult onset neuropathy in cocker spaniels, who is at risk, the inheritance pattern, and the importance of responsible breeding and purchasing practices.

What is Adult Onset Neuropathy?

Adult Onset Neuropathy is a neurological disorder that disrupts the dog's nerve pathways and impair motor functions. Initially, the hind limbs show signs of weakness, trembling, and uncoordinated movements. Eventually, symptoms spread to the front limbs. As the disease progresses, nerves controlling the larynx can be affected, causing swallowing difficulties, aspiration of food or water, which may lead to choking or pneumonia.

Onset typically occurs between seven and eight years of age but always before the dog’s ninth birthday. The progression is gradual, often taking three to four years from the first symptoms to reach its most severe stage. Unfortunately, there is no cure for AON. Treatment focuses on supportive care to manage symptoms. In later stages, euthanasia may be considered to prevent unnecessary suffering when quality of life declines significantly.

Which Dogs Are at Risk?

AON is primarily a disease of the English Cocker Spaniel breed. A small number of cases have been reported in the Field Spaniel breed, particularly where there has been outcrossing to cocker spaniels, introducing breed-specific genetic conditions.

Both males and females are equally susceptible. While affected dogs carry the gene from birth, symptoms only become apparent in later life. Understanding which dogs are at risk is key for breeders and buyers alike.

How is Adult Onset Neuropathy Inherited?

The condition is inherited through an autosomal recessive gene. This means a dog must inherit two copies of the faulty gene — one from each parent — to develop the disease. Dogs inheriting only one copy are carriers; they do not develop symptoms but can pass the gene to offspring.

DNA testing categorises dogs into three groups:

• Clear: No copies of the faulty gene, cannot pass on AON.
• Carrier: One copy of the gene, healthy but can pass the gene to puppies.
• Affected: Two copies of the gene, will develop AON in middle age.

Understanding the genetic status of both parents is essential for predicting the health status of puppies. The inheritance patterns are:

• Two clear dogs produce a clear litter.
• Two affected dogs produce an affected litter.
• Two carriers produce 25% clear, 50% carrier, and 25% affected puppies.
• A clear and an affected dog produce a litter of carriers only.
• A clear and a carrier produce 50% clear and 50% carrier puppies.
• A carrier and an affected dog produce 50% carriers and 50% affected puppies.

Health Testing and Responsible Breeding

Because AON symptoms appear late in life, testing before breeding is critical. UK breeders must use DNA testing to identify the genetic status of their dogs.

Responsible breeders only mate dogs with known clear or carrier status to avoid producing affected puppies. It is important that both prospective parent dogs are tested. Buyers should always request proof of testing for both parents before purchasing a cocker spaniel puppy to help support responsible breeding practices.

These measures not only protect the breed's health but also prevent the emotional and financial hardship associated with caring for affected dogs.

Living with an Affected Dog

For dogs showing signs of AON, management is supportive, focusing on maintaining mobility and preventing choking or aspiration. Assistance with feeding and safe movement may be necessary. Regular veterinary monitoring helps to address complications promptly.

Due to the progressive nature and impact on quality of life, difficult decisions about euthanasia are sometimes required, approached with the dog's welfare as the foremost concern.

Summary and Next Steps

Adult Onset Neuropathy (AON) is a breed-specific, inherited neurological disorder mainly affecting English Cocker Spaniels. It causes progressive limb weakness and swallowing difficulties starting typically after seven years of age. Though incurable, DNA testing provides a powerful tool for breeders and owners to prevent AON and manage its impact.

If you are a breeder or prospective buyer, always check the genetic status of cocker spaniel parents through DNA health testing to preserve the breed's wellbeing. For affected dogs, supportive care and vigilant veterinary attention help ensure their comfort.

For those interested in finding a cocker spaniel puppy, seek reputable breeders who prioritise health screening and responsible breeding practices.