Progressive ataxia is a fatal hereditary defect (lethal mutant) resulting from irreversible changes in the brain and spinal cord. The peripheral nerves do not show any changes. This hereditary defect is insidious because no signs of this disease are seen in calves. The disease usually begins insidiously at 18 to 24 months of age with weakness in the hind legs and crossing of the legs. Signs of this disease are rarely seen in weanlings. Animals over 2 years of age may also still develop the disease. The trigger of progressive ataxia is a single genetic change (mutation) in the gene KIF1C. This gene is non-functional in animals with the hereditary defect progressive ataxia. As a result, there is a progressive breakdown of white matter in specific areas of the brain and spinal cord, resulting in the central nervous deficits of uncoordinated gait, worsening movement disorders, and eventual recumbency. In some animals, abrupt head movements during excitement and intermittent urination can be observed. Males and females are equally affected.
For the hereditary defect progressive ataxia, a genetic test has been developed in France, with which a doubtless diagnosis is already possible in the calf and the matings can be carried out in such a way that no more carriers of the hereditary defect can occur. This mutation in the KIF1C gene is inherited autosomal recessively according to Mendel. This means that the mutated KIF1C gene must be present on both chromosomes for the bovine to express progressive ataxia. Only if both parents carry this mutation in their genome, there can be offspring with this hereditary defect. Charolais breeders and owners need to be especially wary when using young bulls for mating. These young bulls may be undetected carriers of the hereditary defect, as the first signs are usually not visible until 18-24 months of age. For the semen of KB bulls and mating bulls, breeders and animal owners must ensure that the animals are tested for the defective KIF1C gene and are anlage-free for the KIF1C mutation. If this is no longer possible, the offspring should be tested to rule out the occurrence of progressive ataxia later in life.
Charolais cattle with the mutated KIF1C gene on one chromosome (investment carriers) do not develop progressive ataxia, but may pass the defective gene to their offspring with a probability of 50%. These cattle show higher growth rates, which is most likely why selection for this expression of the KIF1C gene occurred. This explains the long persistence of this mutation and the current high frequency of this mutation of 13% in the French Charolais population. Carriers of this mutation must not be bred to each other, as there is a 25% risk of obtaining carriers of the hereditary defect.
Breeders and owners of Charolais or crossbred animals with Charolais can order the DNA test for progressive ataxia at the Institute of Animal Breeding and Genetics of the University of Veterinary Medicine Hannover Foundation. The DNA test will be performed according to the original publication by Duchesne et al. 2018 (Progressive ataxia of Charolais cattle highlights a role of KIF1C in sustainable myelination, PLoS Genet 14(8): e1007550). The attached form should be used to request the DNA test. The form must be signed and can be sent by email, fax or mail. The sample material can be hair roots (approximately 50) from the tail or an EDTA blood sample (3-5 ml). Instructions for sample collection and shipping can also be found here. Until December 31, 2019, the test for progressive ataxia is offered free of charge.
The test result for the expression of the KIF1C gene will be provided to the submitter for each individual animal as follows:
Plant-free (homozygous KIF1C G/G).
trait carrier (heterozygous KIF1C A/G)
trait carrier (homozygous KIF1C A/A)
If animals show signs of ataxia and the test result is trait free or trait carrier, you should contact us. In this case, the animal should not be immediately disposed of, so that further investigations are still possible. All information will be kept strictly confidential and will not be passed on to third parties.