Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter

A review of evidence-based management of infectious ocular surface disease in shelter-housed domestic cats

Infectious ocular surface disease (IOSD) is a common problem in shelter-housed domestic cats and has a widespread negative impact on animal welfare. While the common etiological agents are well-described, addressing IOSD in large groups of animals presents a management challenge to the clinician and logistical challenges to shelter employees. Treatments, diagnostics, and prevention strategies that are effective in privately owned or experimental animals may be impractical or ineffective in the shelter environment. This review article focuses on the relative prevalence of etiological agents in feline IOSD, practical diagnostic testing protocols, prevention strategies, and treatment of IOSD in shelter-housed cats. Discrepancies between experimental laboratory-based studies and clinical trials assessing therapeutics for treatment of feline herpes virus are highlighted. Further high-quality clinical trials are necessary to determine optimal preventative and therapeutic protocols for IOSD in shelter-housed cats.

Chronic Rhinitis in the Cat: An Update

The etiology of feline chronic rhinitis is incompletely understood and often is a diagnosis of exclusion. History, clinical signs, and investigations performed to reach this diagnosis are discussed. Several treatment options are provided, although cure of this frustrating disease is rarely achieved.

Cage size, movement in and out of housing during daily care, and other environmental and population health risk factors for feline upper respiratory disease in nine North American animal shelters

Upper respiratory infection (URI) is not an inevitable consequence of sheltering homeless cats. This study documents variation in risk of URI between nine North American shelters; determines whether this reflects variation in pathogen frequency on intake or differences in transmission and expression of disease; and identifies modifiable environmental and group health factors linked to risk for URI. This study demonstrated that although periodic introduction of pathogens into shelter populations may be inevitable, disease resulting from those pathogens is not. Housing and care of cats, particularly during their first week of stay in an animal shelter environment, significantly affects the rate of upper respiratory infection.

Effect of a synthetic feline facial pheromone product on stress scores and incidence of upper respiratory tract infection in shelter cats

OBJECTIVE To determine whether a synthetic feline facial pheromone product would decrease stress scores and upper respiratory tract infection (URI) incidence in shelter-housed cats. DESIGN Randomized controlled clinical trial. ANIMALS 336 stray, feral, owner-relinquished, or legally impounded cats at 2 animal shelters in northern California. PROCEDURES 5 cat holding rooms (3 at shelter A and 2 at shelter B) were used. A diffuser containing either synthetic pheromone or placebo was randomly assigned to each room, and cats were exposed for a 21-day period. Data collected on each cat included signalment, daily stress scores, and daily URI incidence. After 21 days, diffusers were removed for a 7-day washout period. The type of diffuser in each room was switched, and data were collected for another 21 days. Findings were statistically compared between exposure types and other groupings. RESULTS Cox proportional hazard analysis revealed no significant difference between exposure (pheromone or placebo) and URI incidence. Mixed-effects ordinal logistic regression revealed no significant relationship between exposure and daily stress scores. Three covariates had significant ORs: number of days in holding (OR, 0.80; 95% confidence interval [CI], 0.76 to 0.84), owner-relinquished versus stray (OR, 3.25; 95% CI, 1.18 to 8.94), and feral versus adult cat room at shelter A (OR, 11.10; 95% CI, 4.47 to 27.60). CONCLUSIONS AND CLINICAL RELEVANCE No evidence was found that the evaluated synthetic feline facial pheromone product had any effect on stress scores or URI incidence in shelter-housed cats. Therefore, other established methods for stress and URI reduction should be used in shelter settings.

Polyprenyl Immunostimulant in Feline Rhinotracheitis: Randomized Placebo-Controlled Experimental and Field Safety Studies

Feline rhinotracheitis is a ubiquitous disease caused by feline herpesvirus type 1 (FHV-1). The disease is easily transmissible and common in multi-cat environments where even vaccinated cats can develop clinical signs of respiratory or ocular disease or both when exposed to the virus. Prior to the work reported here, there was no licensed treatment for the disease on the market. We hypothesized that polyprenyl immunostimulant (PI), an immunomodulatory veterinary biologic, would be useful in treating feline rhinotracheitis by reducing the severity of respiratory or/and ocular disease. We conducted double-blinded, randomized, placebo-controlled clinical trials in experimentally infected cats to establish the efficacy of PI. Specific pathogen-free cats were administered a placebo (n = 20) or PI (n = 20) starting on the day of FHV-1 experimental challenge. Trained, masked observers applied a standardized scoring system daily in clinical examinations for 14 days after the FHV-1 challenge. The cats treated with PI had significantly lower disease severity scores over the course of the experiment compared to the cats in the placebo group (p = 0.05). The safety studies, including a field safety study involving 390 owned cats in 10 states, showed that PI was safe to use in cats as young as 8 weeks of age.

Effects of free amino acids on cytokine secretion and proliferative activity of feline T cells in an in vitro study using the cell line MYA-1

In vitro studies might be an interesting screening method for targeted in vivo studies in the field of immunonutrition and help to reduce and refine animal studies. As the role of amino acids for immune function of cats has not been evaluated in detail so far, the present study aimed at investigating the effects of eight different amino acids (arginine, leucine, isoleucine, valine, glutamine, lysine, threonine and tryptophan) in six concentrations each (0, 0.25, 0.5, 1, 2 and 8x the cat blood level) on cytokine secretion and proliferative activity of feline T cells (MYA-1) in vitro. The results demonstrated that high doses of arginine increased IL-4, IL-10 and TNF-α secretion of T cells, while increasing concentrations of lysine increased IL-10 secretion and proliferative activity of the T cells. High doses of leucine enhanced GM-CSF and IL-10 secretion, while concentrations of threonine in the cell culture media greater than blood concentration also increased GM-CSF and additionally TNF-α secretion of the cells. The effects of glutamine and isoleucine on T cell function were only small. In conclusion, the present in vitro study could evaluate the immunomodulating potential of specific amino acids for feline T cell function. High doses of arginine, lysine, leucine and threonine had a significant impact on cytokine secretion and proliferative activity of the T cells. Targeted in vivo studies should investigate the clinical relevance of dietary supplementation of those amino acids in healthy and diseased cats as a next step.

A review of antiviral drugs and other compounds with activity against feline herpesvirus type 1

Feline herpesvirus type 1 (FHV-1) is a common and important cause of ocular surface disease, dermatitis, respiratory disease, and potentially intraocular disease in cats. Many antiviral drugs developed for the treatment of humans infected with herpesviruses have been used to treat cats infected with FHV-1. Translational use of drugs in this manner ideally requires methodical investigation of their in vitro efficacy against FHV-1 followed by pharmacokinetic and safety trials in normal cats. Subsequently, placebo-controlled efficacy studies in experimentally inoculated animals should be performed followed, finally, by carefully designed and monitored clinical trials in client-owned animals. This review is intended to provide a concise overview of the available literature regarding the efficacy of antiviral drugs and other compounds with proven or putative activity against FHV-1, as well as a discussion of their safety in cats.

Something old, something new: Update of the 2009 and 2013 ABCD guidelines on prevention and management of feline infectious diseases

OVERVIEW

The ABCD has published 34 guidelines in two Special Issues of the Journal of Feline Medicine and Surgery (JFMS): the first in July 2009 (Volume 11, Issue 7, pages 527-620) and the second in July 2013 (Volume 15, Issue 7, pages 528-652). The present article contains updates and new information on 18 of these (17 disease guidelines and one special article 'Prevention of infectious diseases in cat shelters'). For detailed information, readers are referred to the guidelines published in the above-mentioned JFMS Special Issues.

Lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats: a systematic review

BACKGROUND

Feline herpesvirus 1 is a highly contagious virus that affects many cats. Virus infection presents with flu-like signs and irritation of ocular and nasal regions. While cats can recover from active infections without medical treatment, examination by a veterinarian is recommended. Lysine supplementation appears to be a popular intervention (recommended by > 90 % of veterinarians in cat hospitals). We investigated the scientific merit of lysine supplementation by systematically reviewing all relevant literature.

METHODS

NCBI's PubMed database was used to search for published work on lysine and feline herpesvirus 1, as well as lysine and human herpesvirus 1. Seven studies on lysine and feline herpesvirus 1 (two in vitro studies and 5 studies with cats), and 10 publications on lysine and human herpesvirus 1 (three in vitro studies and 7 clinical trials) were included for qualitative analysis.

RESULTS

There is evidence at multiple levels that lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats. Lysine does not have any antiviral properties, but is believed to act by lowering arginine levels. However, lysine does not antagonize arginine in cats, and evidence that low intracellular arginine concentrations would inhibit viral replication is lacking. Furthermore, lowering arginine levels is highly undesirable since cats cannot synthesize this amino acid themselves. Arginine deficiency will result in hyperammonemia, which may be fatal. In vitro studies with feline herpesvirus 1 showed that lysine has no effect on the replication kinetics of the virus. Finally, and most importantly, several clinical studies with cats have shown that lysine is not effective for the prevention or the treatment of feline herpesvirus 1 infection, and some even reported increased infection frequency and disease severity in cats receiving lysine supplementation.

CONCLUSION

We recommend an immediate stop of lysine supplementation because of the complete lack of any scientific evidence for its efficacy.

Effects of physiologic concentrations of l-lysine on in vitro replication of feline herpesvirus 1

OBJECTIVE

To evaluate the effects of various concentrations of l-lysine on in vitro replication of feline herpesvirus 1 (FHV-1).

SAMPLE

Cultures of Crandell-Rees feline kidney (CRFK) cells.

PROCEDURES

CRFK cells were inoculated with FHV-1 and maintained in media with 20 combinations of l-arginine and l-lysine concentrations. Changes in cell viability were monitored by continuous measurement of electrical impedance of cultured cells and by observation of viral cytopathic effects. Viral load was determined by use of quantitative PCR assay in supernatants obtained from infected cultures at specified time points.

RESULTS

Increases in l-lysine concentration had no effect on the kinetics of cell death in FHV-1-infected cultures. There was also no significant effect (r(2) < 0.1) on viral DNA load for l-arginine concentrations ≥ 12 μg/mL There was a significant effect of increases in l-lysine concentration on viral DNA load in media supplemented with 6 μg of l-arginine/mL (mean ± SD slope, -4,641 ± 1,626 units; adjusted r(2) = 0.45). However, the difference between the lowest (1 × 10(6.28) copies/μL) and highest (1 × 10(6.86) copies/μL) FHV-1 DNA load in these media was < 1 logarithm.

CONCLUSIONS AND CLINICAL RELEVANCE

The difference in FHV-1 DNA load was unlikely to be biologically important. Various l-lysine concentrations did not inhibit in vitro replication of FHV-1 at l-arginine concentrations sufficient to maintain cell growth. This conclusion was consistent with results of other studies in which investigators have not detected a consistently beneficial effect when l-lysine is administered to FHV-1-infected cats.

ABCD: Update of the 2009 guidelines on prevention and management of feline infectious diseases

OVERVIEW

In this article, the ABCD guidelines published in the JFMS Special Issue of July 2009 (Volume 11, Issue 7, pages 527-620) are updated by including previously unavailable and novel information. For a better picture, the reader is advised to consult that issue before focusing on the novel features.

Ocular manifestations of feline viral diseases

Feline viral diseases are common and cats can be presented with a variety of clinical manifestations. Ocular disease associated with viral pathogens is not unusual, particularly with viruses causing upper respiratory tract disease in cats, such as feline herpesvirus type 1 and feline calicivirus. These agents mainly cause ocular surface disease. Other viruses, such as feline immunodeficiency virus and feline coronavirus, can cause uveitis, while feline leukemia virus can induce ocular lymphosarcoma. This review covers the most common viral pathogens of cats that cause ocular manifestations, the specific features of the ocular diseases caused by these viruses and therapeutic recommendations.

Feline respiratory disease complex

Feline respiratory disease complex (FRDC) refers to the characteristic acute presentation of a contagious respiratory or ocular disease caused by one or multiple pathogens. Environmental and host factors impact the transmission, clinical presentation, preventive strategy, and treatment of affected cats. The FRDC is especially problematic in settings where large numbers of cats cohabit, including animal shelters, catteries, and semi-feral colonies. Although elimination of FRDC is an unrealistic goal, improved understanding can lead to strategies to minimize disease impact.

Snots and Snuffles: Rational Approach to Chronic Feline Upper Respiratory Syndromes

Practical relevance While the most common cause of chronic upper respiratory disease signs in cats is viral disease, with subsequent, self-perpetuating inflammation, other, more discrete causes need to be ruled out. These include foreign bodies, bacterial or fungal infections, oral-dental diseases and neoplasia. Any factors contributing to alterations in the structure or function of the upper airways, including inflammation of any cause, will compromise normal function and predispose to chronic damage if the cat is unable to resolve the underlying factors.

Clinical challenges The chronic feline snuffler is a frustrating patient to treat. The longer the course of disease, the more severe the consequences to affected tissues, and the more debilitated the patient becomes. A logical diagnostic plan to differentiate probable etiologies and to rule out non-viral causes results in appropriate therapeutic choices. Even with a viral etiology, therapies to reduce the pathological consequences of infection may modulate and help control the clinical signs. Some novel choices and drug combinations are discussed in this review.

Patient group Cats of all ages may be affected. Cats with conformational (breed or malformation) characteristics, such as short or convoluted nasal passages or very small nostrils, are predisposed to unresolving inflammation. Fungal disease is more relevant in specific geographic regions, making inclusion of a travel history important in history collection. Older cats are more likely to have neoplasia-induced signs.

Audience This review is directed at all veterinarians who see cats with chronic, recurrent upper respiratory disease.

Treatment of Corneal Ulcers: What are the Medical Options?

Practical relevance Corneal ulcers in cats (ulcerative keratitis) are a common presenting complaint, and are a frequent sequela to feline herpesvirus (FHV-1) infection. In fact, it is fair to assume an FHV-1 aetiology until proven otherwise. In practice, therefore, many cases of corneal ulceration can be treated medically, but treatment can frequently be challenging, with the need to tailor therapy carefully to the type of ulcer, the individual cat and its temperament.

Patient group All age groups and breeds can suffer with ulcerative keratitis although some breeds are over-represented for some types of corneal ulceration.

Evidence base The scientific literature on feline ulcerative keratitis is extensive, particularly that related to FHV-1 infection. This article reviews the medical treatment options for corneal ulceration in cats with reference to the current evidence base.