Progressive cutaneous viral pigmented plaques in three Hungarian Vizslas and the response of lesions to topical tigilanol tiglate gel

Cutaneous pigmented viral plaques is a disorder of epidermal growth caused by canine papillomavirus type 4 (CPV‐4). There is currently no standard of care for managing this condition and it has not been reported in the Hungarian Vizsla. This case series documents the clinical features of canine pigmented viral plaques in Hungarian Vizsla dogs and the treatment of a severe case using a novel topical agent tigilanol tiglate (EBC‐46). A 4‐year‐old spayed Hungarian Vizsla in Australia was presented for multiple cutaneous pigmented plaques extending from the ventral cervical region. Lesions were neither painful nor pruritic. The number and size of these sessile plaques increased over time, with the largest lesions eventually taking on an exophytic (wart‐like) appearance. These lesions did not affect the dog's wellbeing. Two much less severe cases in a 5‐year‐old Vizsla from the UK and a 7‐year‐old Vizsla from New Zealand were also diagnosed. Histology was consistent with papillomavirus‐induced pigmented plaques and CPV‐4 DNA sequences were amplified from paraffin‐embedded formalin‐fixed tissue using the polymerase chain reaction from the most severely affected patient. Topical imiquimod was ineffective although used for only a short time. Two topical applications of novel anti‐neoplastic diterpene ester tigilanol tiglate as a gel, 9 days apart, greatly reduced the size and number of lesions in a limited portion of skin treated, over the lateral hock. While CPV‐4 has been previously reported to cause pigmented plaques, most commonly on pug dogs, but sporadically on other breeds, this is the first report of this virus causing plaques in Hungarian Vizslas. The cases illustrate some of the difficulties in diagnosing papillomavirus‐induced disease in dogs, especially in its early stages. Topical tigilanol tiglate is a potentially useful topical therapy for this viral‐induced disorder of cell growth and represents a treatment deserving of further investigation.