Infectious skin disease in cats, more than you realized (Proceedings)


Pyoderma and bacterial folliculitis in the dog is considered to be very common problems yet in the cat are described as rare or very uncommon in textbooks on small animal dermatology. A study in France of 783 feline derm cases evaluated between 1992 and 1997 diagnosed pyoderma in 4.7%.


Pyoderma and bacterial folliculitis in the dog is considered to be very common problems yet in the cat are described as rare or very uncommon in textbooks on small animal dermatology. A study in France of 783 feline derm cases evaluated between 1992 and 1997 diagnosed pyoderma in 4.7%. Pyoderma does occur in cats and is not rare and similar to dogs is most often a secondary problem. Pyoderma plays a role in feline allergic diseases and as a secondary perpetuating factor in other skin diseases. One reason it may not be recognized as much in the cat in contrast to dogs when an allergic cat with pyoderma has its allergies effectively treated the pyoderma may resolve. Antibiotic therapy is associated with a significant improvement in numerous feline cases that present to dermatology referral practices. Preliminary results of a blinded placebo controlled study on the effects of clavulonic/amoxicillin suggest eosinophilic plaques and lip ulcers are often antibiotic responsive.

Clinical presentations of feline pyoderma are quite variable. For most recognized syndromes there is no age, sex or breed predilections. The more common cases are the superficial pyodermas and folliculitis. Lesions that may be seen include superficial crusts over erosions or papules, moist erythematous erosions, linear crusted erosions and ulcers, moist erythematous plaques. Often these cases are referred in as unresponsive cases of miliary eczema or eosinophilic plaques. In addition many feline indolent ulcers, feline acne and some eosinophilic granuloma have responded to antibiotic therapy. Some cases are seen where antibiotic responsive indolent ulcers may be cured following effective flea control or occur intermittently with allergic flare ups. Another syndrome that is often frustrating to treat but has recently been reported doxycycline responsive is feline plasma cell pododermatitis.[.

The diagnosis of pyoderma is based on the demonstration of organisms and neutrophils in the cutaneous lesions. This is most often accomplished by cytological examination of direct smears from the lesions, or less commonly on histopathologic examination of representative lesions. One study evaluated blinded cytology from 9 control cats and 9 cats with eosinophilic cutaneous plaques and 8 eosinophilic lip ulcers. Of the 9 control cats sampled, 0/180 oil immersion fields from skin were infected. Conversely 143/160 (89.4%) day 0 ECP fields from 9 cats were infected. Only 12/180 (6.7%) fields from the upper lip mucosa of control cats were infected, while 129/160 (80.6%) day 0 ELU fields from 8 cats were infected. All 9 ECP and all 8 ELU lesions showed evidence of bacterial infection in at least one field, while none of the 9 normal cats showed skin infection and 3/9 showed mucosal infection. Preferable there will be intracellular bacteria as well and occasionally intracellular bacteria may be seen in macrophages or eosinophils. Some of these cases likely reflect secondary pyoderma and may be more prevalent in cats with chronic skin diseases that have been treated with long term or repetitive glucocorticoid therapy.

Treatment is best accomplished with systemic antibiotic therapy. Therapy is more difficult than in the dog for several reasons. Many cats are more difficult to medicate and the incidence of vomiting or diarrhea is somewhat higher. I generally try amoxicillin trihydrate/clavulanate potassium (Clavamox, Pfizer) 62.5 mg BID, Clindamycin HCL 11-22mg/kg q24h or ormetoprim sulfadimethoxine (Primor, Pfizer) 120 mg once a day as initial empirical therapy. If fluoroquinolones are going to be used I prefer marbofloxacin (Zeniquin, Pfizer) 1.5 to 2.2mg/kg because if has not been shown to cause retinal disease as higher dose enrofloxacin (Baytril, Bayer) may.

Malassezia dermatitis

Malassezia is a genus of yeast that originally contained three species. M. pachydermatis is found primarily in small animal and is most common though M. sympodialis and M. globosa have also been found in cats with skin or ear disease. Malassezia otitis externa and media is the most common problem in cats. In some cases it will only be found from the middle ear and not the ear canal. No specific studies in Malassezia complicated otitis have been done regarding age, breed or sex predilections. The yeast is considered as secondary causes that lead to the perpetuation of disease. Skin lesions may also be seen with or without concurrent otitis. Early lesions may appear relatively normal or be slightly erythematous. A light gray to yellow scale crust or brown crust is often present. Pruritus is variable but may be intense. In the cat the favorite localized sites are chin (acne differential), face (may complicate idiopathic facial dermatitis), and interdigital. Generalized or regional disease is the least common form in the cat and may be associated with seborrhea oleosa, paraneoplastic alopecia and may carry a poor prognosis. Diagnosis is based on cytology showing Malassezia and any may be significant from skin sites but in ears more that 3 per 1000x (oil immersion field) is needed to be significant.

Topical therapy is not very helpful in cats and systemic therapy is preferred. Systemic therapy is most commonly accomplished with ketoconazole 2.5 - 10mg/kg q24. It is best given with food as an acid gastric environment stimulates absorption. In the rare case ketoconazole is ineffective then itraconazole 5-10mg/kg q24hr or fluconazole 5mg/kg q24h may be used.

Viral Dermatitis

Feline herpes virus 1 is a common cause of conjunctivitis and rhinotracheitis but has been described as a rare cause of dermatitis in cats. Herpes dermatitis though rare has been confirmed in cats and appears to have some typical features. It is characterized by ulcerative dermatitis of the nasal planum and haired skin of the face. It is important to note that in the Hargis study 6 of 9 cats had been previously diagnosed as having eosinophilic dermatitis compatible with eosinophilic granuloma complex or allergic dermatitisThe presence on intranuclear inclusions had been overlooked in original biopsies and evaluations. This complex could easily be confused as well with mosquito bite hypersensitivity and idiopathic facial dermatitis if it occurred in Persian cats. It is important therefore that clinicians are familiar with this condition and that they alert their pathologists when performing skin biopsies in cases with compatible clinical findings. Lesions tended to be chronic and though resolved in one case later recurred at the same site. The single case report also was chronic recurrent and was a nasal facial dermatitis associated with recurrent upper respiratory disease and corneal ulcers. This cat sounded more severely affected and may have been immunocompromised as well. It also developed paronychia and scrotal dermatitis. Somewhat similar lesions have been reported and well documented in cheetahs.

The cases described by Hargis et al were variable in age from 4 months to 16 years old and a Persian and Himalayan were two of the cases. All 9 cats had facial nasal or lesions affecting both areas. Five cats had a history of conjunctivitis or ocular discharge and 5 had a history of upper respiratory infection. Eight cats had been treated with systemic glucocorticoid therapy and either worsened or were unaffected by the treatment.

Therapy options described for herpes dermatitis are oral alpha interferon, imiquimod, lysine and acyclovir. The newest is Imiquimod 5% (Aldara, 3M pharmaceuticals). It is a topical cream that is considered a immune response modifier. It does not directly have antiviral properties but kills virus by stimulating natural immune defenses which theoretically imparts a more sustaining natural resistance. Imiquimod stimulates cytokine production especially interferon alpha, interferon gamma and IL-12. The IL 12 may be especially important as that cytokine appears to correlate best with resolution of HPV induced warts in humans. In addition imiquimod stimulates langerhans cells resulting in their activation and maturation which promotes their early response to keratinocytes altered by neoplastic change or viral infections and makes them more potent activators or CD4+ T cells. It should be applied once daily for two to three consecutive days each week.

Another new treatment option is the use of low dose interferon. Though interferon is not new, the following regimen is, PO as an oral wash at 1,000IU daily or 3,000IU eod.

Papilloma Virus and Bowens disease

There are at least two main types of papilloma virus in cats with one (FdPV-2) mainly causes oral mucosal lesions often under the tongue. In the skin there may be more than one papilloma virus as one has been related to what is now called feline sarcoid and affects mesenchymal cells below the epidermis while another has been found in epithelial cells and some work has shown these may be closely related to the human papilloma virus. Another report isolating a papillomavirus from a skin lesions showed it more similar to the canine virus suggesting we may have up to three different papillomavirus in cat skin disease.

Bowens disease in cats is multicentric squamous cell carcinoma in situ. Papilloma virus has been detected in about half of the cases. Immunohistochemical staining has been more accurate in detecting the virus than electron microscopy, though some cases do show compatible intranuclear particles. Bowens disease is seen more in older cats and usually has multiple lesions typically 3mm to 3 cm in diameter. Most commonly they are on the head, face or forelegs though anywhere may be affected. Lesions most often are hyperpigmented plaques with a rough hyperkeratotic surface though some have a greasy surface or are lightly pigmented.

Surgical removal was the treatment of choice in the past but trial therapy with Imiquimod may be beneficial and the use in papilloma virus was the initial indication for its use in humans. Oral (low dose usually 1,000 to 3,000 IU q24-72hrs) or systemic interferon 200,000 to 1 million IU subcutaneously every day to weekly has also been reported effective. Azithromycin was recently reported effective in canine papillomatosis but its use in cats has not yet been reported.


Bourdeau, P. and F. Fer, Characteristics of the 10 most frequent feline skin disease conditions seen in the dermatology clinic at the National Veterinary School of Nantes. Vet Dermatol, 2004. 15(s): p. 63.

Wildermuth, B.E., C.E. Griffin, and W.S. Rosenkrantz, Feline pyoderma therapy. Clin Tech Small Anim Pract, 2006. 21(3): p. 150-6.

Bettenay, S.V., et al., Prospective study of the treatment of feline plasmacytic pododermatitis with doxycycline. Vet Rec, 2003. 152(18): p. 564-6.

Wildermuth, B.E., C.E. Griffin, and W.S. Rosenkrantz, Response of feline eosinophilic cutaneous plaque and eosinophilic lip ulcers to amoxicillin-clavulonate (Clavamox) therapy: a randomized, double blind placebo controlled prospective study. Submitted to Vet Derm 2010.

Mauldin-Daniel, E.A., D.O. Morris, and M.H. Goldschmidt, Retrospective study: the presence of Malassezia in feline skin biopsies. A clinicopathological study. Vet Derm, 2002. 13(1): p. 7-13.

Hargis, A., et al., Ulcerative facial and nasal dermatitis in cats associated with feline herpesvirus 1. Vet Dermatol, 1999. 10: p. 267-274.

Wilhelm, S., et al., Clinical, histological and immunohistochemical study of feline viral plaques and bowenoid in situ carcinomas. Vet Dermatol, 2006. 17(6): p. 424-431.

Munday, J.S., et al., Detection of papillomaviral sequences in feline Bowenoid in situ carcinoma using consensus primers. Vet Dermatol, 2007. 18(4): p. 241-5.

J S Munday1, E.M.H., L Howe, R A Squires, A F French, Feline cutaneous viral papilloma associated with human papillomavirus type 9. Vet Pathol, 2007. 44(6): p. 924-927.

Terai, M. and R.D. Burk, Felis domesticus papillomavirus, isolated from a skin lesion, is related to canine oral papillomavirus and contains a 1.3 kb non-coding region between the E2 and L2 open reading frames. J Gen Virol, 2002. 83(Pt9): p. 2303-2307.

Yagci, B.B., et al., Azithromycin therapy of papillomatosis in dogs: a prospective, randomized, double-blinded, placebo-controlled clinical trial. Vet Dermatol, 2008. 19(4): p. 194-198.

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