Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease

Abstract

To determine the effectiveness of dietary lysine supplementation in cats with enzootic upper respiratory disease (URD), 50 cats were fed a ration containing 11 or 51 g lysine/kg diet for 52 days. Food intake, body weight, clinical signs, plasma amino acid concentrations and presence of Chlamydophila felis or feline herpesvirus (FHV)-1 DNA within the conjunctival fornix were assessed. Food and lysine intake of both dietary groups decreased between days 17 and 22, coinciding with peak disease and viral presence. Mean disease score for cats fed the supplemented ration (0.94) was higher than for those fed the basal diet (0.21); however, this could be attributed to a small subset of male cats which demonstrated fighting behavior that may have contributed to stress within that cage. FHV-1 DNA was detected on 12 occasions in six cats receiving the supplemented diet and on one occasion in one cat fed the basal diet. C felis DNA was never detected. Mean plasma arginine concentration was lower and plasma lysine concentration was higher in supplemented cats. Mean plasma arginine concentration declined throughout the study in both dietary groups. Data from the present study raise important questions but do not permit a definitive conclusion regarding the efficacy of dietary lysine supplementation in cats with enzootic URD.

Feline Herpesvirus-1

“…68 ✜ In a larger study, addition of lysine to the diet of 50 cats with enzootic upper respiratory tract disease actually increased the severity of clinical signs and FHV-1 DNA detection rates. 69 ✜ In a large clinical study within an animal shelter (144 treated cats, 147 controls), dietary lysine supplementation did not reduce FHV-1 infection rates in the experimental group compared with the control group. 70 ✜ Another large controlled study involving 261 animal shelter cats reached similar conclusions, with lysine-dosed cats developing more severe clinical signs and higher FHV-1 DNA detection rates than control cats.…”

Feline herpesvirus

“…It may therefore be of use early in acute disease or as a means of reducing the severity of disease and virus shed at times of stress: suggested dosage regimens are described elsewhere [82,128]. There is evidence that dietary lysine supplementation is not effective in groups of cats and that maybe bolus administration is essential [84]. Bovine lactoferrin has shown some in vitro activity most likely by preventing attachment and penetration of FeHV-1 into susceptible cells [2], but in vivo efficacy has not yet been evaluated.…”

Infectious Diseases

“…179 It is optimal when used early in infection, or as a means to prevent recrudescence during stress, where it has been shown to reduce viral shedding in latently infected cats. 183 However, food intake (and therefore lysine intake) decreased when lysine was added to the diet. 243 In fact, one study actually found increased viral shedding and severity of signs of URTD in shelter cats fed lysine supplements.…”

“…243 In fact, one study actually found increased viral shedding and severity of signs of URTD in shelter cats fed lysine supplements. 183 In one study, plasma arginine concentrations declined in lysine-supplemented cats during a 52-day monitoring period, leading the authors to recommend monitoring of plasma arginine in cats receiving long-term lysine supplementation. 183 However, food intake (and therefore lysine intake) decreased when lysine was added to the diet.…”

“…62 In another study evaluating the effectiveness of dietary lysine supplementation in shelter cats with enzootic upper respiratory disease, mean disease scores were higher for cats fed the lysine-supplemented diet. 183 As the overlying epithelia necroses, the lesions ulcerate and become inflamed. In addition, cats in the study were group housed and group fed so that individual lysine intake could not be monitored.…”