Toxoplasma gondii and Alternaria sp.: An Original Association in an Immunosuppressed Dog with Persistent Skin Lesions

Abstract

Dogs and cats may suffer from a variety of diseases, mainly immune mediated, that require the administration of immunosuppressive drugs. Such therapies can cause adverse effects either by the toxicity of the drugs or as a consequence of immune suppression and associated opportunistic infections. Here we present an, yet unknown, association of Toxoplasma gondii and Alternaria fungus, within cutaneous lesions in a dog under long-term immunosuppressive therapy. The diagnosis of such infections is laborious and not obvious at first glance, since the clinical signs of cutaneous toxoplasmosis, neosporosis or alternariosis are not specific. A further laboratory confirmation is needed. Therefore, we currently recommend that dogs and cats should undergo serologic testing for toxoplasmosis or neosporosis prior to immunosuppressive therapy and a regular dermatological evaluation during the immunosuppressive therapy.

Keywords: Alternaria; Toxoplasma gondii; immunosuppressive therapy; skin lesions.

Figure 1

Thorax nodule (left) and fine-needle aspiration cytology (right). Numerous crescent-shape elements (5 × 3 μm) consistent with protozoan tachyzoites (arrow head), yeast-like elements (arrow) and a parasitophorous vacuole filled with tachyzoites (star) were observed.

Figure 2

Punch biopsy of the thorax nodule (A). Focally extensive pyogranulomatous inflammation of the upper dermis with scattered 10 µm diameter spheric microorganisms and moderately hyperplastic epidermis (HE stain). (B). Perivascular to diffuse pyogranulomatous dermatitis; few tachyzoites (Ta, arrow) and spherical structures evocative of fungal chlamydospores (Chl, arrowhead) are visible (HE stain). (C). Heavy colonization of hair (endothrix) and hair shaft by PAS-positive fungal filaments (hyphae, Hy, arrows). (D). Immunohistochemistry for Toxoplasma gondii, numerous immunolabelled (brown) protozoan tachyzoites scattered throughout dermis and epidermis. (E). Spheric fungal structures (chlamydospore-like elements, Chl, arrowheads) and immunolabelled (brown) parasitophorous vacuoles filled with tachyzoites (Ta, arrows).