Prototheca wickerhamii in a dog with cutaneous, ocular and systemic manifestations and treatment with terbinafine

Abstract

A two-year-old intact female collie presented with a tentative diagnosis of systemic blastomycosis based on compatible clinical signs and history and a positive urine Blastomyces antigen enzyme immunoassay. The dog was subsequently correctly diagnosed with protothecosis based on ocular and paw pad histopathology and in vitro culture of Prototheca wickerhamii from paw pad tissue. Histopathology revealed organisms in deep tissue samples as well as in the epidermis and superficial keratin layers of the paw pad. Serum (1→3)-β-d-glucan testing was negative. The dog was treated with terbinafine based on in vitro susceptibility results. There are no previous reports of terbinafine use for the treatment of canine protothecosis. Neurological and gastrointestinal symptoms remained stable with terbinafine. While there was an overall improvement in cutaneous lesions and attitude over the course of eight weeks on treatment, the animal did not survive despite therapy.

Cutaneous protothecosis in a dog successfully treated with oral itraconazole in pulse dosing

“…Our case was such a case with clinical signs restricted exclusively to the nasal plane and foot pads of the animal. Macro-and microscopic aspects of the skin lesions were similar to those observed in other dogs with cutaneous involvement [ 8 , 13 ].…”

“…Administration of terbinafine has been advocated as a treatment for human protothecosis of the skin, when patients do not respond to azole therapies [ 5 ]. It should be noted that in the only report that used terbinafine for the treatment of canine protothecosis, despite its in vitro activity, the drug partially controlled the lesions but failed to contain the infection, leading to the animal’s death [ 13 ].…”

“…Canine protothecosis has mainly been caused by P. bovis [ 11 , 12 , 15 ]. Infections due to P. wickerhamii seems to be more rare [ 13 ].…”

Intralesional amphotericin B in a cat with cutaneous protothecosis

“…Terbinafine, an allylamine antifungal, was selected based on the cat's poor response to azoles. In addition, oral terbinafine has been reported to stall the systemic progression of protothecosis in a dog, while improving cutaneous lesions 11 …”

“…Intralesional use of amphotericin B has been reported in cats for the treatment of feline sporotrichosis 10 . Oral terbinafine was used in a case of disseminated protothecosis in a dog, stalling the progression of disease with the improvement of cutaneous lesions, despite the fatal outcome expected in most of the disseminated infections, 11 and also has been mentioned by some authors as a possible option against Prototheca spp 1 . Combination therapy is likely to be superior to monotherapy with a single azole in most cases of Protothecosis 1 .…”