PRA-b
PRA (Progressive Retinal Atrophy) What is PRA? In PRA, the retina disappears; the blood vessels that feed the retina and remove waste products become thinner and smaller and their number decreases and the rods and cones disappear. The cat's vision deteriorates (night blind) and eventually becomes completely blind. At the end of the disease, all photoreceptors (rods and cones) with which humans and animals can see have disappeared and the pigment epithelium (gives eye color) is also affected. There is (yet) nothing to do against the disease. PRA does not develop until later in life. Symptoms: The symptoms associated with PRA are: enlarged pupil, nystagmus (involuntary rhythmic rapid eye movements), hyperreflexia of the tapetum lucidum (the light-reflecting layer of cells directly behind or sometimes in the retina that allows the eye to see better visible in the dark), progressive narrowing of the retinal blood vessels and degeneration of the rods and cones. Inheritance: PRA has an autosomal recessive form (rdg) and an autosomal dominant form (Rdy). The autosomal recessive variant occurs in most cats. The frequency of occurrence is low. The recessive form is often discovered late, usually after the affected individuals have already produced offspring. The dominant form leads to noticeable symptoms at a much younger age than the recessive form. This makes it easier to keep out of breeding than the recessive form. Two forms of PRA have been identified in the Abyssinian and Somali: the recessive form, which manifests itself at 18-24 months of age, and the dominant form, which manifests itself at 4-5 weeks of age. In the Persians, the disease is seen at 12-15 weeks. This is thought to be the recessive form of PRA. In the Siamese and, presumably, the Oriental Shorthair, symptoms of PRA are seen at 3 weeks of age. This is seen as a family relationship. PRA-b A variant of Pra specific to the breed has been found from the first bloodlines of the Bengal. By examining many Bengalis suffering from a form of blindness, who had a negative result on the 'normal' Pra test, it was concluded that they were dealing with a variant of Pra. This variant may have been found in the wild (ALC) line of the first Bengal cats. Based on this knowledge, laboratories have started working with the DNA material of Bengals suffering from blindness and have been able to develop a test from that which breed specifically works for the Bengal. This is the Pra-B test. This also means that only the Pra-B test can be used for Bengal cats and the normal Pra test for cats has no value for this breed.