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Cowpox in humans is a rare zoonotic disease; its recognition is therefore problematic due to the lack of clinical experience. The differential diagnosis includes other poxvirus infections and also infections with herpesviruses or selected bacteria. The clinical course can be complicated and the improvement may take weeks. Late diagnosis is one of the causes of unnecessary combined antibiotic therapy or surgical intervention. A case of cowpox after a cat scratch in a 15-year-old girl is presented, with a summary of the available clinical data on cowpox infections.

The present report describes a case of generalized cowpox virus infection with necrotizing facial dermatitis in a cat and a likely transmission to an animal keeper. The viral aetiology was confirmed by histopathology, immunohistochemistry, PCR, virus isolation, DNA sequencing and electron microscopy. Histopathological examination of the cat's skin revealed a severe, necrotizing dermatitis with ballooning degeneration and hyperplasia of epithelial cells with pathognomonic cytoplasmic eosinophilic inclusion bodies. Additionally, at post-mortem examination, a systemic poxvirus infection was detected affecting pancreas, thymus, lymph node, liver and lung. The human patient's skin biopsy revealed an ulcerative dermatitis with epidermal hyperplasia and ballooning degeneration. Serological investigation displayed a high orthopoxvirus-specific antibody titre in the human patient. Environmental factors increase the natural reservoir host population for cowpox viruses, such as voles, which results in a higher risk of infection for cats and subsequently for humans. Due to this zoonotic potential, a cowpox virus infection must be considered as an aetiological differential in cases of necrotizing dermatitis in cats., (© 2011 The Authors. Journal compilation © 2011 ESVD and ACVD.)

History and Admission Findings: A 36-year-old woman initially noticed a red spot, about pea-sized, with a central pimple over the right eyebrow and a swollen submandibular lymph node. A pressure-sensitive, 4 cm large, node developed out of this small spot, with a central, black, tightly-adhering crust bearing several varioliform vesicles around its edge. In addition to swelling of the right half of the face, the patient had a fever up to 39.5 degrees C, general malaise, nausea and vomiting. Various antibiotics were ineffective. The woman was hospitalized with a diagnosis of facial erysipelas. She owned a cat which had developed a purulent nodule on a forepaw a few days before onset of the patient's disease. LABORATORY TEST: ESR and CRP were moderately elevated, no leukocytosis and blood cultures were sterile. Wound smears showed colonization with Klebsiella pneumoniae and Enterobacter cloacae., Diagnosis, Treatment and Course: The patient's general condition improved under initially calculated antibiotic dosages, which was later adapted to the measured resistance. The black-crusted nodes became larger, however, and incision was performed on the 8 th day after hospitalization, under the suspicion of fluctuation. However, no pus was removed, but there was massive inflammatory infiltration of the soft tissue. Examination of samples of skin and part of the crust revealed orthopox virus (cowpox virus). Spontaneous healing followed within 3 weeks, leaving only a small scar., Conclusions: This was a cowpox virus in the sense of a zoonosis transmitted by the cat. In Germany, now that smallpox has been eradicated, the clinical presentation of infections with the orthopox virus, which are closely related to variola virus, are too little recognized. Atopic and immunocompromised patients are at risk of a cutaneous dissemination with a more severe course of the infectious illness; even a lethal outcome has been reported in Germany.

In a 21-year-old woman, suffering from a moderate painful erythematous infiltrated lesion in the neck, cowpox was diagnosed. Contact with an infected cat was suggested. Healing was spontaneous.

An 18-year-old patient requiring steroid treatment for severe bronchial asthma and with atopic dermatitis acquired a cowpox-like virus infection clinically similar to smallpox from a domestic cat as carrier. In spite of intensive care, with controlled pressure breathing and the last available vaccinia hyperimmunoglobulin, the patient died of pulmonary embolism although viral spread had ceased some days before.