A slamming door, an unexpected clap, or even a sudden stroke. For the vast majority of dogs, a loud sound or an unforeseen touch causes a brief surprise, a small jump followed by curiosity or indifference.
This reaction, which is distressing for both the animal and its family, is not a simple problem of fear or behaviour. It is a congenital neurological disorder known as startle disease. Understanding how the dog's brain works in these moments is the first step to approaching the situation with empathy and seeking the appropriate preventive answers.
What is startle disease or hyperekplexia in dogs?
Startle disease, medically termed hyperekplexia, is a neurological disorder that causes exaggerated physical responses to sudden sensory stimuli, whether unexpected noises or physical contact.
To understand it simply, the dog's nervous system experiences a failure in the transmission of signals responsible for inhibiting movement. When a stimulus reaches the brain, the body "overreacts", sending contraction signals to all muscles at the same time without the usual filter that softens the response.
A fundamental and differentiating aspect of this pathology is that the dog's consciousness remains completely intact during the episodes. Although its body becomes absolutely rigid and seems to suffer a collapse, the animal knows at all times what is happening around it, which makes it vital to maintain a calm environment during the episode.
Main symptoms: How to identify the warning signs
Hyperekplexia usually manifests in the first weeks of the animal's life. Affected puppies begin to show abnormal responses in everyday handling situations or in noisy environments. The most common warning signs include:
- Generalised muscle stiffness: When startled, the puppy becomes "petrified", often with all four limbs stretched out and a stiff neck.
- Intense tremors: These can be triggered by handling the puppy, lifting it, or by high-pitched sounds.
- Spasms and motor difficulty: After the startle, the animal may present spasmodic movements or take a few moments to recover the ability to move normally.
As a reassuring note for caregivers, these neurological symptoms are directly linked to the state of alertness. When the puppy is deeply relaxed or sleeping, the stiffness and tremors usually disappear or decrease.
The hereditary origin and genetically vulnerable dog breeds
Startle disease does not develop from trauma or contagion; it is a strictly genetic condition. It is caused by alterations in specific genes (mainly the SLC6A5 or GLRA1 genes) that are responsible for regulating neurotransmitters in the brainstem and spinal cord.
It is transmitted through an autosomal recessive inheritance pattern. This means that for a puppy to develop symptoms, it must inherit two copies of the mutated gene (one from the father and one from the mother).
Autosomal recessive inheritance scheme:
- Clear dog: Does not have the mutation. It will not get sick or transmit the disease.
- Carrier dog: Has only one copy of the mutation. It generally does not present symptoms, but can transmit it to its offspring.
- Carrier + carrier cross: If two healthy but carrier dogs are crossed, there is a 25% chance of puppies being born affected by the disease, a 50% chance of healthy carriers being born, and a 25% chance of them being born clear.
Different genetic variants associated with this disease have been identified in breeds such as the Irish Wolfhound, the Spanish Greyhound, the Miniature Australian Shepherd, and the Bobtail, although it can occur in mixed breeds that share this genetic load.
Prevention is key
Since a carrier dog does not show any symptoms throughout its life, genetic analysis is a fundamental tool to prevent the appearance of startle disease in new litters, by allowing the identification of carriers.
The Koko Genetics dog DNA test offers a useful tool for breeders and families. Through a simple and painless saliva sample, it is possible to identify whether a dog is clear, a carrier, or affected long before any breeding is planned or the first clinical symptoms appear. Knowing the genetic status of the parents allows for responsible breeding decisions, always crossing in an informed manner to progressively reduce the presence of variants associated with this disease in breeding lines and decrease the risk of affected puppies being born.
However, it is important to remember that this test is not intended for diagnostic purposes and that any result with clinical implications must be confirmed by a diagnostic genetic analysis in a clinical laboratory.
Ensuring a dog's quality of life starts long before its birth, and genetics today gives us the opportunity to protect its neurological well-being from day one. Discover the full report on genetic diseases in dogs from Koko Genetics, thoroughly understand your pet's health profile, and take the step towards truly informed and responsible breeding and ownership.
