Thor, a 9 month old domestic short hair kitten presented with a 2 week history of vomiting, weight loss, progressive ataxia and generalized weakness, which had progressed to nonambulatory paraparesis. A pronounced physiologic nystagmus and intermittent rotary nystagmus was also noted at the initial exam. Withdrawals, superficial pain and menace responses were intact.
Hematological and serum biochemistry abnormalities at the initial exam included lymphopenia, (718 uL; reference interval 850-5850 uL) mild hypoalbuminemia, and an A/G ratio of 0.4 (albumin, 2.5 g/dL; reference interval, 2.6‐3.9 g/dL; globulin, 5.6 g/dL; reference interval, 3.0‐5.9 g/dL). Tests for Toxoplasmosis, FeLV and FIV were negative, and FCoV antibody titer was positive at 1:6400.
Thor declined rapidly after exam, with progressive paresis and dysphagia. Uveitis was also noted in his right eye.
Treatment with GS-441524 was initiated at 25 mg/kg BID, for the first week, and then weaned down to 25 mg/kg SID for the remaining 11 weeks. A higher dose than the standard starting neurological FIP dose was chosen due to Thor's critically worsening condition.
Within 24 hours of starting treatment with GS-441524, Thor began to show reduction in the amount of paresis. Within 4 days, Thor regained crude ambulatory ability which progressively improved throughout treatment.
After 6 weeks of treatment previously noted hematological and serum biochemistry abnormalities had normalized. (Lymphocytes, 2875 uL; reference interval 850-5850 uL; albumin, 3.0 g/dL; reference interval, 2.6‐3.9 g/dL; globulin, 3.6 g/dL; reference interval, 3.0‐5.9 g/dL; A/G ratio: 0.8)
Other than some mild gait abnormalities which appear to be permanent residual effects, Thor is clinically normal as of 1 year post treatment.
Video timeline of resolution of neurological symptoms
Day 0: Thor is nearly immobile
Day 1: Some rear leg movement is regained, several hours after second dose
Day 3: Additional movement
Day 4: First steps
8 Weeks (Thor is in the camouflage sweater)