Feline morbillivirus (FeMV) has been associated with renal lesions in cats; however, a clear association between infection and the development of chronic kidney disease (CKD) remains to be elucidated.

With the aim of characterizing urinary findings, urinalysis, urine chemistry and qualitative proteinuria results were retrospectively evaluated in 14 cats with RT-PCR positive urine for FeMV (FeMV+). FeMV+ were compared to 21 CKD and 22 healthy blood donor cats. For all of the animals the following information was available: signalment, history, physical exam, clinicopathological evaluation including CBC, serum chemistry profile, urinalysis including urine specific gravity (USG), dipstick, sediment examination, urine protein-to-creatinine ratio (UPC), fractional excretion of electrolytes, urine SDS-PAGE stained with Coomassie blue, and urine culture. Kidney histopathology and immunohistochemistry for FeMV were evaluated at necropsy (n=3). Data were analysed with descriptive statistics and compared using non-parametric tests (Kruskal-Wallis test). P-values <0.05 were considered significant.

The FeMV+ were outdoor domestic shorthaired cats, 8 neutered males, 6 females (5/6 spayed), median age was 35 months (range 14–101). FeMV+ had significantly decreased USG (median 1054, range 1022–1065) and urine creatinine (median 227.23 mg/dl, range 83.02–489.75) when compared to healthy subjects (median 1067, range 1040–1080, p<0.00001; median 406.50 mg/dl, range 195.32–575.58; p<0.00001; respectively). No statistical differences were detected for serum creatinine (median 0.81 mg/dl, range 0.67–2.13 vs. median 1.46 mg/dl, range 0.78–2.13) and urea (median 45.35 mg/dl, range 30.20–63.30 vs. median 46.47 mg/dl, range 31.47–73.01) and for electrolyte fractional excretions. All urine cultures were negative.

A significant increase in UPC was observed in FeMV+ (median 0.19, range 0.08–1.03) when compared to healthy subjects (median 0.10, range 0.04–0.40, p<0.0003), while statistical differences were not detected between infected cats and CKD cats (median 0.23, range 0.10–0.80). In FeMV+, SDS-PAGE qualitative proteinuria showed differences if compared to the healthy cats. In particular, a tubular pattern was evidenced, with a decrease of uromodulin and an increase in the number and intensity of low molecular weight proteins, indicating a renal involvement, although less severe than in CKD cats. Renal pathology showed tubulo-interstitial nephritis and positive immunohistochemical stain for FeMV-N protein in tubular cells.

Urine findings in FeMV+ suggest the presence of early tubulo-interstitial damage characterized by tubular proteinuria and mild reduction of urine concentrating ability. No urine electrolyte handling dysfunctions were detected. Further prospective studies combining long-term patient follow-up, renal pathology and urine evaluation are warranted to obtain a better characterization of potential FeMV-associated renal damage.

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