CACA - CNS Atrophy with Cerebellar Ataxia
22.01.2023 17:33


CNS (Central Nervous System) Atrophy and Cerebellar Ataxia (CaCa / CA4) is a neurological condition in Belgian Shepherd Dogs that manifests itself through uncoordinated movements. This disease is caused by a mutation (deletion) of the SELENOP gene.

With this hereditary disease, the uptake of the trace element selenium in the central nervous system is reduced, resulting in neurological deficits. Selenium is an essential - vital - trace element for humans and animals and protects nerve cells in the brain. It is also required by the immune system, among other things, for the formation of immune cells. Affected puppies already show uncoordinated movements and trembling of the limbs (intention tremor) at the age of two weeks, whereby the severity of the symptoms can vary from case to case. In addition, increased muscle tone can occur, as well as disturbances in the swallowing reflex and brief episodic spastic attacks.

The total selenium levels in the blood of homozygous mutant puppies of the examined litter were reduced to about 30% of the value of a homozygous wild-type littermate. Genotyping of >600 Belgian Shepherd Dogs revealed an additional homozygous mutant dog. This dog also suffered from pronounced ataxia, but lived to the age of 10 years. This retrospectively identified fifth case apparently showed a milder and more or less stable clinical condition. It seems possible that the level of dietary selenium intake has an impact on the clinical variability. Given the findings in Selenop -/- mice, a diet high and constant selenium levels may be beneficial for affected puppies if their disease is diagnosed early enough.

Puppies affected by CACA are often euthanized after veterinary assessment for poor quality of life. The neurological disease is inherited in a monogenic autosomal recessive manner. The birth of affected puppies can be safely ruled out if care is taken when mating that at least one of the two breeding animals is free of the genetic defect.

Case study: Malinois litter with 8 puppies

A Belgian shepherd litter of the Malinois variety with 8 offspring was examined. One male and three females were presented with ataxia. The other four puppies and the parents were clinically normal. The clinical examination was carried out on the 27th day after birth. Affected puppies presented with trunk wobble, intention tremor, general increased muscle tone, decreased swallowing reflex, and brief episodic spastic episodes of varying intensity

Affected puppy exhibits trunk wobble and intention tremor (click for Video)

Affected puppy is unable to stand, exhibits slight tremors and severely uncoordinated movements (click for Video)

First obvious signs were observed at 12-14 days after birth and developed progressively thereafter. The four affected puppies gained less body weight (mean 1.8 kg) compared to the four unaffected littermates (2–3 kg). They were euthanized on day 27 after birth for animal welfare reasons. Except for slight anemia, no gross lesions were detectable at autopsy. Histologically, all four animals showed similar lesions in the brain and spinal cord to varying extents. In the cerebellum, all cortical layers were atrophic with depletion of Purkinje cells and granule cells. Neuroaxonal degeneration was present in the midbrain, brainstem and spinal cord.

Video compilation provided by the breeder:

In the study, the deletion was genotyped in a cohort of 668 Belgian Shepherd dogs. This cohort included the index family of four CACA-affected atactic dogs, 13 ataxia cases with known pathogenic variants from previous SDCA1 and SDCA2 studies, and 20 additional unexplained ataxia cases from the Vetsuisse biobank.
None of the previously reported SDCA1 and SDCA2 cases carried the SELENOP deletion. However, one of the archived cases of unexplained ataxia from the University of Bern Biobank was also homozygous for the deletion. This dog developed ataxia as a puppy and died at the age of 10 years. It is said to be from a litter of 10 puppies, three of which were euthanized when they were just a few weeks old due to severe ataxia. The other case was distantly related to the four affected puppies from the index family

The pedigree shows that the mutation can currently be traced back to the mating of Onix von Löwenfels x Virginia von Löwenfels and well-known sires such as Kirou Airport Hannover and his sons Antrax vom Zabelstein and Enox der Sonne entgegen or Engie Airport Hannover with their offspring Alf vom Nordhang der Eifel and Assi von der Steinteichmühle are among the carriers.


Christen M, Högler S, Kleiter M, Leschnik M, Weber C, Thaller D, Jagannathan V, Leeb T. Deletion of the SELENOP gene leads to CNS atrophy with cerebellar ataxia in dogs. PLoS Genet. 2021 Aug 2;17(8):e1009716. doi: 10.1371/journal.pgen.1009716. PMID: 34339417; PMCID: PMC8360551.

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