Propensity towards aggressive behaviour

Aggression in dogs is the most serious behavioural problem that has been discussed for a long time. As the human health may be endangered, the general effort is focused on understanding the character of this aggression and on explaining its genetic background. Although aggression in specific dog breeds is desired, its unwanted expression in impermissible situations is possible. The aggressive behaviour of a dog can be caused by bad health condition, the way the dog has been raised and trained. These factors really present a particularly important aspect that should be primarily considered. First, the owner should evaluate objectively whether there are some changes in dog´s health condition or mistakes in dog´s training.  Genetic predisposition can be other factor that may be responsible for sudden aggression in some dog breeds.

Idiopathic aggression (aggression caused by unknown reasons) has been observed especially in Malinois dog breed. In the dogs concerned, seizures associated with aggressive behaviour with no recognizable trigger can occur. Seizure-associated aggressive behaviours have been described as episodic, unplanned, motiveless, unpredictable, out-of-the character of the dog concerned. The dogs that suffer from rage episodes get a glazed look in their eyes, show lack of response to any stimuli, and do not take any notice of its surrounding.

The aggression seizures relate to the neurotransmitter dopamine. The dopamine transporter gene (SLC6A3) is associated with the production of dopamine transporter that is responsible for dopamine transport through presynaptic membrane into the neuron. Lit et al. (2013) identified in SLC6A3 gene 3 polymorphisms. The first of the polymorphisms detected is Poly(A) insertion of 12 nucleotides (A22) that have been primarily found in Malinois dog breed. This variant is associated with sudden and unpredictable behavioural changes.  Further, an 18-nucleotide deletion has been found (A0) in most breeds evaluated.  Within the study, there has been detected another variant (A10) present in Boxer breed.

In general, aggression and sudden behavioural changes are mainly associated with genotype A22/A22. In individuals that carry at least one allele A22 and have a genotype A0/A22 or A10/A22, the unpredictable aggression may occur as well. The genotypes A0/A0, A0/A10 a A10/A10 are not associated with episodic aggression.

Genotype inheritance:

• A0/A0 Genotype A0/A0 is not associated with episodic aggression.
• A0/A10 Genotype A0/A10 is not associated with episodic aggression.
• A10/A10 Genotype A10/A10 is not associated with episodic aggression.
• A0/A22 Genotype A0/A22 can be associated with unpredictable or undesired behaviour.
• A10/A22 Genotype A0/A22 can be associated with unpredictable or undesired behaviour.
• A22/A22 Genotype A22/A22 is associated with unpredictable or undesired behaviour.

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