Feline herpes dermatitis treated with interferon omega

Interferon therapies in small animals

Interferons (IFNs) are cytokines that play an important role in the immune response of animals and humans. A number of studies reviewed here have evaluated the use of human, canine and feline IFNs as treatments for infectious, inflammatory and neoplastic disease in dogs and cats. Recombinant canine IFN-γ is deemed an efficacious therapy for canine atopic dermatitis. Recombinant feline IFN-ω is effective against canine parvoviral enteritis and has also been recommended for canine atopic dermatitis. Based on limited evidence, recombinant canine IFN-α could be a topical treatment option for dogs with gingivitis and keratoconjunctivitis sicca. Conclusive evidence is lacking for other diseases and large randomised controlled trials are needed before IFNs can be recommended for other indications.

FELINE HERPESVIRUS INFECTION IN FOUR CAPTIVE CHEETAHS (ACINONYX JUBATUS) POSTVACCINATION

Cheetahs (Acinonyx jubatus) are particularly susceptible to feline herpesvirus-1 (FHV-1). Recommendations for preventive health care in cheetahs include vaccination against FHV-1 using killed and modified live virus (MLV) vaccines. Although MLV vaccines tend to induce a more robust immune response than killed vaccines, they can induce disease. This case series details an FHV-1 outbreak in four adult cheetahs following the use of MLV vaccine in one of them. All four cheetahs developed severe FHV-1 clinical signs and were euthanized. Clinical signs included depression, anorexia, nasal discharge, ocular discharge, sneezing, and ulcerative dermatitis. Herpesvirus infection was diagnosed using history, clinical signs, polymerase chain reaction, and histologic evaluation. The timeline of events suggests the MLV vaccine was the inciting cause, although this was not conclusively proven. Outcome of this case suggests that when considering MLV vaccines for cheetahs, careful risk and benefit discussions are merited.

TREATMENT OF CHRONIC HERPESVIRAL DERMATITIS IN A CAPTIVE CHEETAH (ACINONYX JUBATUS) IN NAMIBIA

A 9-yr-old male cheetah (Acinonyx jubatus) housed at the Cheetah Conservation Fund in Namibia developed cutaneous lesions consisting of alopecia, erythema, ulceration, and crusting on the left fore and hind limbs. Histopathology of skin biopsies in conjunction with indirect fluorescent antibody and polymerase chain reaction testing confirmed a diagnosis of feline herpesvirus-1 dermatitis; microbial culture indicated secondary bacterial infection. Therapy included targeted systemic antimicrobial and antiviral treatment, topical medications, and repeated cryotherapy. Lesions exhibited varying degrees of clinical improvement but, overall, progressed in extent, size, and severity during the subsequent 2.5 yr of intense treatment. The cheetah was ultimately euthanized due to a guarded prognosis and concerns about poor quality of life. Potential factors initiating or contributing (or both) to the severity and nonhealing nature of the cutaneous lesions include chronic unidentified stress, altered immune system function, and other environmental influences.

Evaluation of intranasal vaccine administration and high-dose interferon- α2b therapy for treatment of chronic upper respiratory tract infections in shelter cats

Clinical signs of upper respiratory tract infection can be hard to manage in cats, particularly those in shelters. In this study, clinical data were collected from chronically ill (3-4 weeks' duration) cats with suspected feline herpesvirus-1 (FHV-1) or feline calicivirus (FCV) infections after administration of one of two novel therapies. Group A cats were administered a commercially available formulation of human interferon-α2b at 10,000 U/kg subcutaneously for 14 days, and group B cats were administered one dose of a FHV-1 and FCV intranasal vaccine. Molecular assays for FHV-1 and FCV were performed on pharyngeal samples, and a number of cytokines were measured in the blood of some cats. A clinical score was determined daily for 14 days, with cats that developed an acceptable response by day 14 returning to the shelter for adoption. Those failing the first treatment protocol were entered into the alternate treatment group. During the first treatment period, 8/13 cats in group A (61.5%) and all 12 cats in group B (100%) had apparent responses. The seven cats positive for nucleic acids of FHV-1 or FCV responded favorably, independent of the treatment group. There were no differences in cytokine levels between cats that responded to therapy or failed therapy. Either protocol assessed here may be beneficial in alleviating chronic clinical signs of suspected feline viral upper respiratory tract disease in some cats that have failed other, more conventional, therapies. The results of this study warrant additional research involving these protocols.

Pulmonary cowpox in cats: five cases

Case series summary

This case series documents five cases of pneumonia (with pleural effusion in three cases) caused by cowpox virus (CPxV) in domestic cats. Predisposition to pneumonia may have resulted from mixed infections in two cases (feline herpesvirus and Bordetella bronchiseptica in one cat, and Mycoplasma species in the other).

Relevance and novel information

As well as diagnostic confirmation by previously described methods of virus isolation from skin lesions, and demonstration of pox virions in skin samples using electron microscopy and inclusion bodies in histological preparations, this is the first report of diagnosis by virus isolation from bronchoalveolar lavage fluid or pleural fluid, and demonstration of inclusion bodies in cytological preparations. This is also the first series to report treatment with interferon omega (IFN-ω). Two cats survived, both of which had been treated with IFN-ω. As CPxV represents a serious zoonotic risk it is an important differential diagnosis of pneumonia in cats.

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.

The innate antiviral immune system of the cat: molecular tools for the measurement of its state of activation

The innate immune system plays a central role in host defence against viruses. While many studies portray mechanisms in early antiviral immune responses of humans and mice, much remains to be discovered about these mechanisms in the cat. With the objective of shedding light on early host-virus interactions in felids, we have developed 12 real-time TaqMan(®) qPCR systems for feline genes relevant to innate responses to viral infection, including those encoding for various IFNα and IFNω subtypes, IFNβ, intracellular antiviral factor Mx, NK cell stimulator IL-15 and effectors perforin and granzyme B, as well as Toll-like receptors (TLRs) 3 and 8. Using these newly developed assays and others previously described, we measured the relative expression of selected markers at early time points after viral infection in vitro and in vivo. Feline embryonic fibroblasts (FEA) inoculated with feline leukemia virus (FeLV) indicated peak levels of IFNα, IFNβ and Mx expression already 6h after infection. In contrast, Crandell-Rees feline kidney (CrFK) cells inoculated with feline herpes virus (FHV) responded to infection with high levels of IFNα and IFNβ only after 24h, and no induction of Mx could be detected. In feline PBMCs challenged in vitro with feline immunodeficiency virus (FIV), maximal expression levels of IFNα, β and ω subtype genes as well as IL-15 and TLRs 3, 7 and 8 were measured between 12 and 24h after infection, whereas expression levels of proinflammatory cytokine gene IL-6 were consistently downregulated until 48h post inoculation. A marginal upregulation of granzyme B was also observed within 3h after infection. In an in vivo experiment, cats challenged with FIV exhibited a 2.4-fold increase in IFNα expression in blood 1 week post infection. We furthermore demonstrate the possibility of stimulating feline immune cells in vitro with various immune response modifiers (IRMs) already known for their immunostimulatory properties in mice and humans, namely Poly IC, Resiquimod (R-848) and dSLIM™, a synthetic oligonucleotide containing several unmethylated CpG motifs. Stimulation of feline PBMCs with dSLIM™ and R-848 effectively enhanced expression of IFNα within 12h by factors of 6 and 12, respectively, and Poly IC induced an increase in Mx mRNA expression of 28-fold. Altogether, we describe new molecular tools and their successful use for the characterization of innate immune responses against viruses in the cat and provide evidence that feline cells can be stimulated by synthetic molecules to enhance their antiviral defence mechanisms.

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.

Immunohistological evaluation of feline herpesvirus-1 infection in feline eosinophilic dermatoses or stomatitis

This study used immunohistochemistry (IHC) and histopathology to evaluate the presence of feline herpesvirus-1 (FHV-1) in feline cases of 'eosinophilic granuloma complex' (EGC) or other eosinophilic dermatoses or stomatitis, diagnosed at the Veterinary Pathology Diagnostic Service, University of Sydney between January 1996 and June 2008. Two of the 30 cases (6.6%) examined showed positive immunoreactivity to FHV-1 using IHC. Intranuclear inclusion bodies were also detected on histopathological examination of haematoxylin and eosin stained sections of both cases but were very difficult to find. Therefore, FHV-1 is uncommonly associated with EGC or other eosinophilic dermatoses or stomatitis in Sydney. However, misdiagnosis as an EGC lesion or other eosinophilic dermatoses may occur if inclusion bodies are overlooked or absent on histopathology and this may significantly decrease the chance of a favourable treatment outcome. FHV-1 should be considered in cats with severe ulcerative cutaneous or oral lesions, unresponsive to corticosteroid treatment, with or without concurrent or historical signs of upper respiratory tract or ocular disease more typical of FHV-1. IHC may be helpful in differentiating FHV-1 dermatitis or stomatitis from other eosinophilic lesions, which is of vital clinical and therapeutic importance.

Frequency of apoptotic keratinocytes in the feline epidermis: a retrospective light-microscopic study of skin-biopsy specimens from 327 cats with normal skin or inflammatory dermatoses

A retrospective light-microscopic study was performed on 294 biopsy specimens of haired skin from cats with various feline inflammatory dermatoses and specimens from cats with normal skin. Conditions expected to frequently have apoptotic epidermal keratinocytes (AKs) (including erythema multiforme, systemic lupus erythematosus, thymoma-associated exfoliative dermatitis, solar dermatitis, and viral dermatopathies) were found to have significantly more AKs than other types of inflammatory dermatoses. Nevertheless, we found more than two AKs in many skin-biopsy specimens from inflammatory conditions not expected to have frequent AKs (especially those from ectoparasitic dermatoses). Only a single AK was found in 1/33 cats with normal skin.

Occurrence, morphological characterization and antigen localization of felid herpesvirus-induced pneumonia in cats: a retrospective study (2000-2006)

The pathological findings in nine cases of pneumonia associated with infection by felid herpesvirus-1 (FeHV-1) are presented. The animals affected were five kittens, two subadult cats and two adult cats. The microscopical changes included fibrinonecrotic pneumonia and severe necrosis of the bronchial and bronchiolar epithelium. FeHV-1 antigen was detected immunohistochemically in pneumocytes, alveolar macrophages and necrotic bronchial and bronchiolar epithelial cells. In the youngest kitten viral antigen was also found in the liver. FeHV-1 infection should therefore be considered as a differential diagnosis in cats with fibrinonecrotic pneumonia and demonstration of viral antigen by immunohistochemistry is a useful diagnostic procedure in such cases.

Treatment of feline herpesvirus-1 associated disease in cats with famciclovir and related drugs

BACKGROUND

Feline herpesvirus 1 (FHV-1) is a common cause of ocular and upper respiratory disease in cats and kittens, and a potential cause of eosinophilic dermatitis.

HYPOTHESIS

The systemic anti-herpes drug, famciclovir (Famvir; Novartis), would be effective in the clinical management of disease attributable to FHV-1, including conjunctivitis, keratitis, corneal sequestra, rhinosinusitis and FHV-1 associated dermatitis.

CLINICAL OUTCOME

Oral famciclovir was used to treat signs considered referable to FHV-1 in 10 cats: four had primary ocular disease, two had rhinosinusitis and four had FHV-1 associated dermatitis. Patients treated in Australia (five cats) and Europe (one cat) were given 62.5 mg of famciclovir once or twice daily. Four cats treated in the USA were given 125 mg three times daily. Famciclovir was uniformly well tolerated and, in all cases, had a positive impact on the patient's condition. The apparent improvement in lesions was superior to what had been achieved previously using other therapeutic strategies. One cat with severe destructive rhinosinusitis was significantly improved by a 4-month course of famciclovir in combination with antibacterials. Corneal sequestra detached in two out of three cats treated; cats with ocular signs were qualitatively more comfortable, with reduced clinical signs and an improved appearance of the eyes. Critically, oral famciclovir therapy was considered more convenient than topical ocular therapy. All four cats with FHV-1 associated dermatitis improved substantially, although relapse occurred subsequently in three patients. A further cat with presumptive FHV-1 associated dermatitis responded to topical aciclovir cream before famciclovir could be sourced.

CONCLUSIONS

Famciclovir appears to be a promising systemic drug for treating diseases associated with FHV-1 infection. More rigorous clinical trials are required to optimise the dosing regimen for safe and effective specific anti-herpes treatment in feline clinical medicine.