Molecular test for recessive progressive retinal atrophy (b-PRA) of the Bengal cat, an early-onset hereditary photoreceptor degeneration caused by the c.1000G>A (p.Ala334Thr) variant in the KIF3B gene. Affected cats progressively lose rod and cone vision and may become blind within the first year of life. The test reports clear/carrier/affected status and does not detect other forms of feline PRA.

b-PRA documented in the Bengal, Savannah, Highlander and Highlander Shorthair cats (OMIA:002267-9685). In the Toyger it is not recorded in OMIA (limited data).

- Night blindness and difficulty seeing in low light in kittens a few weeks old\n- Progressive decrease in daytime visual acuity\n- Mydriasis and reduced pupillary reflex in advanced stages\n- Complete blindness within the first year in severe cases\n- Fundus with vascular attenuation and progressive retinal degeneration

Bengal b-PRA was described clinicopathologically by Ofri et al. (2015), who characterised an early-onset autosomal recessive retinal degeneration in the breed by electroretinography and pedigree analysis. The causal variant in KIF3B (c.1000G>A, p.Ala334Thr) was identified by exome/genome sequencing and published in the context of the study of ciliopathies caused by KIF3B mutations (Cogné et al., 2020). The DNA test was added to the breed screening.

- Screen Bengal, Savannah and Highlander breeding animals before mating\n- Do not mate two carriers: 25 % affected offspring\n- Carriers may be mated to clear animals; test the offspring intended for breeding\n- Avoid breeding affected animals\n- Record the status in the pedigree to reduce the spread of the allele, also present in derived lines (Savannah/Highlander)

Differential diagnosis with other feline PRAs (including dominant forms and those associated with other genes) and with acquired retinopathies (hypertension, taurine, infectious). The test rules out only the KIF3B c.1000G>A variant; a negative result does not exclude other causes of blindness. In humans, KIF3B mutations cause autosomal dominant ciliopathy; the feline variant is associated with recessive PRA.

1. Ofri R et al. 2015. Characterization of an Early-Onset, Autosomal Recessive, Progressive Retinal Degeneration in Bengal Cats. Invest Ophthalmol Vis Sci. PMID: 26258614
2. Cogné B et al. 2020. Mutations in the Kinesin-2 Motor KIF3B Cause an Autosomal-Dominant Ciliopathy. Am J Hum Genet. PMID: 32386558
3. Mowat FM et al. 2025. Consensus guidelines for nomenclature of companion animal inherited retinal disorders. Vet Ophthalmol. PMID: 38334230
4. OMIA:002267-9685.