Feline sporotrichosis in Asia

Abstract

Sporothrix schenckii sensu lato is currently recognized as a species complex with only Sporothrix brasiliensis, Sporothrix schenckii sensu stricto, Sporothrix globosa and Sporothrix pallida identified to cause disease in the cat. Feline sporotrichosis in Asia is mainly reported from Malaysia where a single clonal strain of clinical clade D, Sporothrix schenckii sensu stricto manifesting low susceptibility to major antifungal classes, has been identified as the agent of the disease. Sporothrix globosa has been identified to cause disease from a single cat in Japan while the specific species of agent has not been identified yet for the disease in Thailand. Despite efforts to elucidate and describe the pathogenicity of the agent and the disease it causes, the paucity of data highlights the need for further molecular epidemiological studies to characterize this fungus and the disease it causes in Asia. Its prognosis remains guarded to poor due to issues pertaining to cost, protracted treatment course, zoonotic potential and low susceptibility of some strains to antifungals.

Keywords: Asia; Feline sporotrichosis; Malaysia.

Fig. 1

A solitary chronic, non-healing and exudative lesion at the paw of a cat with sporotrichosis

Fig. 2

Chronic, non-healing ulcers on the bridge of the nose by S. schenckii sensu stricto infection of a cat in Malaysia. Note that small granulomas are forming at the tip of both ears

Fig. 3

As the disease progresses, non-encapsulated granulomas form that then ulcerate at ear tips. These exudate then dry to form crusts

Fig. 4

Some cats are presented with generalized, chronic, non-healing nodular lesions at the thorax extending to the abdomen, not just at the head and ear tips

Fig. 5

A dorsal view of a cat with pyogranulomatous nodular and exudative lesions at the ear tips, highlighting the preponderance of the fungus to aggregate at the cooler regions of the host

Fig. 6

Colony morphology of S. schenckii sensu stricto. Black mycelial form colony was observed on Sabouraud glucose agar after culture at 28 °C for 14 days (a). White yeast-like colony was observed on Sabouraud glucose agar after culture at 37 °C for 10 days (b)

Fig. 7

Yeasts are found in abundance from direct impression smears from the feline patient. They are located intra and extracellularly, in pleomorphic shapes ranging from cigar-shaped to round or oval, measuring 3–5 μm in diameter with a thin, clear halo around a pale blue cytoplasm. Haemacolor stain

Fig. 8

Diffuse pyogranulomatous inflammation is seen throughout the superficial and deep dermis that may extend to the deeper subcutis

Fig. 9

Round to cigar-shaped organism, seen both free and within macrophages. Commonly, the yeast in cytoplasm of macrophages creates large clear pockets full of yeast due to poorly visualized yeast cell wall

Fig. 10

A cat with Cryptococcosis. The involvement of the nasal sinuses and occasional cutaneous spread of the disease often confuses the veterinarian between cryptococcosis with that of sporotrichosis

Fig. 11

A cat with squamous cell carcinoma (SCC) confirmed via histopathology. As the most common form of malignant neoplasm of the feline skin, SCC is associated with sun-damaged skin with the nasal planum, pinnae and eyelids the most common affected sites. Its clinical predisposition site and appearance may be easily confused with that of sporotrichosis

Fig. 12

A cat with herpesvirus-1 (feline rhinotracheitis) infection. There is extensive ulcerative and necrotizing dermatitis involving the nasal planum, bridge of nose and periocular skin with concurrent respiratory signs. Very similar with those of a cat with sporotrichosis with lesion extension to the nasal sinus which causes secondary respiratory dyspnoea. Image courtesy of Dr. Francesco Albanese

Fig. 13

A cat with an erosive and ulcerative nodular lesion at the left peri-nasal orifice caused by Mycobacterium microti which is clinically very similar with sporotrichosis. Image courtesy of Prof. Danielle Gunn-Moore

Fig. 14

Post-healing ear tip deformity due to extensive tissue necrosis from infection