Thiamine (vitamin B1) is a water-soluble vitamin functioning as an essential cofactor in carbohydrate metabolism. Cats require high levels of thiamine in their diets for normal metabolic function, and exclusive feeding of a thiamine-deficient diet can lead to clinical signs of deficiency within four weeks that can be rapidly fatal if left untreated. Here we describe four cases of clinical thiamine deficiency in cats in the United Kingdom associated with exclusive feeding of a defective commercial dry kibble. Cats ranged between 1.5 and 6 years of age, and were all exclusively fed the defective diet for at least four weeks prior to onset of acute neurologic signs. Neurological examination variably revealed depressed mental status, mydriasis, severe generalized ataxia, delayed postural reaction in all four limbs, decreased menace response in both eyes, positional nystagmus and cervical ventroflexion. MRI scans of the brain in all cats revealed bilateral symmetrical lesions at the level of the caudal colliculi and caudate nuclei that were T2W and FLAIR hyperintense, T1W isointense and non-contrast enhancing, consistent with a metabolic encephalopathy. Analysis of the diet at an external laboratory confirmed severely low thiamine levels (1.2–3.8 mg thiamine/kg dry matter basis; the NRC RA for adult feline maintenance is a minimum of 5.6 mg of thiamine/kg dry matter). Rapid clinical improvement was documented in all cases within 24 hours of initiating parenteral thiamine administration. All four cats survived, but one has significant persistent neurologic deficits and another has mild behavioral abnormalities reported by the owner six months post diagnosis that are suspected to now be permanent.

The cases described above represent only the second reported major outbreak of clinical thiamine deficiency occurring due to defective dry cat food as opposed to canned. In contrast to this previously reported outbreak, all cats here presented with acute neurologic signs as the initial presenting complaint rather than nonspecific GI signs initially. Full reporting of the number of affected cats is still pending analysis by the company, but they have indicated that numerous other clinical cases have been identified thus far and none of the primary care veterinarians assessing these patients had thiamine deficiency considered as a potential differential diagnosis upon review of the records. Increased awareness of the clinical presentation of thiamine deficiency will hopefully help raise diagnostic rates for this condition in the future.

Disclosures

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