Cutaneous viral dermatoses often remain underdiagnosed in cats, not only due to their relative rarity but also due to the inherent complexity in precisely identifying the causal agent.
Introduction
Among these conditions, infection with feline herpesvirus type 1 (FHV-1) plays a predominant role in feline dermatology. While this infection is primarily known for its respiratory and ocular manifestations as part of the cat flu syndrome, its dermatological expressions deserve particular attention. This review aims to analyze in depth the cutaneous aspects of FHV-1 infection, incorporating the latest advances in both diagnosis and therapy.
Etiology and Virological Characteristics
Feline herpesvirus type 1 belongs to the genus Varicellovirus of the Alphaherpesvirinae subfamily. This classification phylogenetically links it to canine herpesvirus type 1, with which it shares many biological and structural characteristics. The virion is distinguished by a complex architecture comprising a double-stranded DNA protected by an icosahedral capsid, itself enveloped by a glycoprotein-lipid bilayer. This sophisticated structure confers particular biological properties on the virus, notably a relative fragility in the external environment, its survival being limited to approximately 18 hours in a humid environment and even further reduced in dry conditions.
This sensitivity to environmental factors and common disinfectants is mainly explained by the presence of the lipid envelope, which makes the virus particularly vulnerable to physico-chemical aggressions. While this characteristic facilitates environmental decontamination, it also highlights the importance of direct transmission in the spread of the virus within feline populations.
Pathogenesis and Mechanisms of Infection
The pathogenesis of cutaneous herpetic infection is part of a complex process involving several distinct phases. Initial contamination classically occurs via the respiratory or ocular route, with the virus demonstrating a marked tropism for mucous and cutaneous epithelia. This tissue affinity explains the preferential localization of lesions at mucocutaneous junctions.
A fundamental characteristic of FHV-1, common to all alphaherpesviruses, lies in its ability to establish latency in the trigeminal ganglion after primary infection. This property creates a permanent viral reservoir, a potential source of subsequent reactivations. Viral reactivation, a key element in the pathogenesis of clinical manifestations, can occur spontaneously, but it is most often triggered by various environmental or physiological stress factors.
Among these triggering factors are particularly environmental changes such as moving or introduction into a multi-cat household, stressful physiological situations such as gestation, and medical interventions including surgery or the administration of glucocorticoids. Identifying these factors is crucial in implementing an effective therapeutic and preventive strategy.
Clinical Expression of the Disease
Primary Cutaneous Manifestations
The dermatological manifestations of FHV-1 infection are primarily characterized by an ulcerative dermatitis preferentially localized to the nasal and ophthalmic mucocutaneous junctions. This cutaneous involvement may follow an upper respiratory infection or occur concomitantly with conjunctivitis or herpetic keratitis.
The evolution of lesions follows a characteristic sequence beginning with the appearance of vesicles that rapidly progress to ulcers. These ulcerations are generally not painful and progressively become covered with crusts. The healing process can lead to the formation of residual alopecia. In some cases, the lesions can extend beyond the classic peri-orifice areas to affect the oral mucosa, paw extremities, or even the abdomen.
Photo 1: Superinfected feline herpesvirus
Systemic and Respiratory Manifestations
The clinical picture is frequently accompanied by systemic manifestations including marked lethargy, hyperthermia, and anorexia. Respiratory involvement is classically manifested by marked sneezing and nasal discharge initially serous, evolving towards a mucopurulent appearance. Conjunctivitis, often bilateral, also constitutes a cardinal sign of the infection.
Particular Clinical Forms
Herpes-Associated Erythema Multiforme
A particular form of erythema multiforme associated with FHV-1 infection has been documented in scientific literature. This manifestation, considered a specific immune reaction, is characterized by annular or polycyclic lesions presenting a symmetrical distribution on the face. The identification of this particular clinical form requires a specific diagnostic approach and adapted therapeutic management.
Chronic and Recurrent Infections
The potential chronicity of the infection and the risk of recurrences constitute major aspects of the disease. Reactivation episodes can be more or less severe and frequent depending on individuals and environmental factors. Understanding this infection dynamic is essential to establish a long-term therapeutic strategy.
Diagnostic Approach
Clinical Assessment
The diagnosis of cutaneous feline herpes virus relies on a methodical approach combining the analysis of clinical and epidemiological elements with the results of complementary examinations. A detailed anamnesis, particularly seeking recent stress factors and medical history, constitutes the first step of this approach. The clinical examination must be meticulous and systematic, paying particular attention to the respiratory and ocular systems as well as the precise characterization of skin lesions.
Complementary Examinations
Histopathology
Histopathological examination of the lesions is a cornerstone of diagnosis. Skin biopsies typically reveal vesicular and necrotizing dermatitis characterized by epidermal hyperplasia associated with areas of necrosis. The inflammatory infiltrate has a mixed composition with a predominance of eosinophils. The discovery of basophilic intranuclear inclusion bodies in the surface and adnexal epithelium represents a major, albeit not pathognomonic, diagnostic element.
Molecular and Immunological Techniques
Recent advances in the field of molecular diagnostics have enabled the development of more specific and sensitive techniques. PCR performed on unfixed tissue offers excellent sensitivity for the detection of the viral genome. Immunohistochemical analyses allow the demonstration of viral antigens in lesional tissues. In situ RNA hybridization (RNA-ISH) constitutes a promising new approach for virus detection in tissues.
It is important to note that the search for serum antibodies is of little diagnostic interest due to possible interference with vaccine antibodies and those from previous natural infections.
Therapeutic Strategy
Famciclovir
Famciclovir currently represents the reference antiviral in the treatment of FHV-1 infection. Its administration at a dosage of 40 to 90 mg/kg two to three times a day has proven effective in controlling clinical manifestations. The duration of treatment must be adapted to clinical evolution and can extend over several weeks. Renal function monitoring is necessary during treatment due to the molecule’s potential nephrotoxicity.
Other Options
Other molecules can be considered in the therapeutic strategy. Azithromycin, administered at a dose of 10 mg/kg once a day for 10 days, has shown some efficacy. Topical treatments, particularly acyclovir applied daily or imiquimod used two to three consecutive days per week, can usefully complement the systemic approach.
Immunomodulation
Interferons
The use of interferons constitutes an interesting complementary therapeutic approach. Feline omega interferon can be administered at a dose of 1.5 MU/kg intraperitoneally and subcutaneously. Interferon alpha-2a, used at a rate of 1000 units orally once a day in a cycle of 21 days of treatment followed by 7 days off, represents a possible alternative.
Supportive Care
Supportive care is particularly important in overall management. Systemic and/or ophthalmic antibiotic therapy may be necessary to control secondary bacterial superinfections. Local care should be adapted to the nature and location of the lesions. It is crucial to emphasize the formal contraindication of corticosteroids, the use of which would risk aggravating the viral infection by compromising local immune defenses.
Prevention and Follow-up
Environmental Management
Prevention of recurrences constitutes an essential aspect of long-term management. It relies primarily on the identification and control of stress factors likely to trigger viral reactivation. Optimization of living conditions and rigorous environmental hygiene are key elements of this preventive approach.
Clinical Surveillance
Regular patient follow-up allows evaluation of treatment efficacy and adjustment of management if necessary. Therapeutic response is assessed on the evolution of skin lesions, the regression of associated clinical signs, and improvement of general condition. The persistence or recurrence of clinical manifestations should lead to a re-evaluation of the therapeutic strategy.
Conclusion
Feline cutaneous herpesvirus represents a complex clinical entity whose management requires a global and personalized approach. Recognition of characteristic dermatological manifestations, combined with a rigorous diagnostic approach, allows rapid implementation of adapted treatment. Recent advances in understanding pathogenic mechanisms and the development of new therapeutic options contribute to optimizing the management of clinical cases. Nevertheless, the potential chronic nature of the infection and the risk of recurrences emphasize the importance of regular follow-up and a well-constructed preventive strategy. Therapeutic success relies on the judicious combination of available treatment modalities and appropriate management of environmental factors.
Bibliography
- Coyner, K. (2020). Distinguishing Between Dermatologic Disorders of the Face, Nasal Planum, and Ears: Great Lookalikes in Feline Dermatology. Veterinary Clinics of North America: Small Animal Practice, 50(4), 823-882. doi: 10.1016/j.cvsm.2020.03.008
- Nagata, M., & Rosenkrantz, W. (2013). Cutaneous viral dermatoses in dogs and cats. Compendium on Continuing Education for the Practicing Veterinarian, 35(7), E1. PMID: 23677843
- Linek, M., Rüfenacht, S., Brachelente, C., von Tscharner, C., Favrot, C., Wilhelm, S., … & Welle, M. (2015). Nonthymoma-associated exfoliative dermatitis in 18 cats. Veterinary Dermatology, 26(1), 40-45, e12-3. doi: 10.1111/vde.12169
- Gutzwiller, M. E., Brachelente, C., Taglinger, K., Suter, M. M., Weissenböck, H., & Roosje, P. J. (2007). Feline herpes dermatitis treated with interferon omega. Veterinary Dermatology, 18(1), 50-54. doi: 10.1111/j.1365-3164.2007.00556.x
- De Lucia, M., Cabref, M., Denti, D., Mezzalira, G., Rondena, M., & Tommaso, C. (2021). Presumptive herpesvirus-associated erythema multiforme in a cat. Veterinary Dermatology, 32, 86-e16. doi: 10.1111/vde.12901
Related Searches
feline herpesvirus, cat, herpes, respiratory tract, animal, herpes virus, symptoms, virosis, virus, clinical signs, disease, feline, community, viral disease, prevention, cause, case, treatment, parturition, kittens, face, herpes virosis, manner, infection, cornea, diagnosis, conjunctiva, time, skin, carriers, breeding, vaccine, anti-inflammatories, surface, reason, crises, age, pcr, contamination, phases, discharge, contact, manifestations, duration, level, example, eyes, involvement, conjunctivitis, tonsils, point, fever, origin, amino acid
