Sporotrichosis can be diagnosed in domestic and wild mammals. In veterinary medicine it is most frequently seen in cats and horses. Cats have a particularly severe form of cutaneous sporotrichosis and also can serve as a source of zoonotic infection to persons who handle them and are exposed to exudate from skin lesions.

Sporotrichosis (also known as "rose gardener's disease") is a disease caused by the infection of the fungus "Sporothrix schenckii". This fungal disease usually affects the skin, although other rare forms can affect the lungs, joints, bones, and even the brain. Because roses can spread the disease, it is one of a few diseases referred to as "rose-thorn" or "rose-gardeners' disease".

Because "S. schenckii" is naturally found in soil, hay, sphagnum moss, and plants, it usually affects farmers, gardeners, and agricultural workers. It enters through small cuts and abrasions in the skin to cause the infection. In case of sporotrichosis affecting the lungs, the fungal spores enter through the respiratory pathways. Sporotrichosis can also be acquired from handling cats with the disease; it is an occupational hazard for veterinarians.

Sporotrichosis progresses slowly – the first symptoms may appear 1 to 12 weeks (average 3 weeks) after the initial exposure to the fungus. Serious complications can also develop in patients who have a compromised immune system.

If symptoms of histoplasmosis infection occur, they will start within 3 to 17 days after exposure; the average is 12–14 days. Most affected individuals have clinically silent manifestations and show no apparent ill effects. The acute phase of histoplasmosis is characterized by non-specific respiratory symptoms, often cough or flu-like. Chest X-ray findings are normal in 40–70% of cases. Chronic histoplasmosis cases can resemble tuberculosis; disseminated histoplasmosis affects multiple organ systems and is fatal unless treated.

While histoplasmosis is the most common cause of mediastinitis, this remains a relatively rare disease. Severe infections can cause hepatosplenomegaly, lymphadenopathy, and adrenal enlargement. Lesions have a tendency to calcify as they heal.

Presumed ocular histoplasmosis syndrome (POHS) causes chorioretinitis, where the choroid and retina of the eyes are scarred, resulting in a loss of vision not unlike macular degeneration. Despite its name, the relationship to "Histoplasma" is controversial. Distinct from POHS, acute ocular histoplasmosis may rarely occur in immunodeficiency.

Dermatophytids are fungus-free disseminated skin lesions resulting from induced sensitization in patients with ringworm infections.

The most common dermatophytid is an inflammation in the hands resulting from a fungus infection of the feet. Dermatophytids normally disappear when the primary ringworm infection is treated.

Dermatophytids may resemble erythema nodosum.

In absence of proper treatment and especially in immunocompromised individuals, complications can arise. These include recurrent pneumonia, respiratory failure, fibrosing mediastinitis, superior vena cava syndrome, pulmonary vessel obstruction, progressive fibrosis of lymph nodes. Fibrosing mediastinitis is a serious complication and can be fatal. Smokers with structural lung disease have higher probability of developing chronic cavitary histoplasmosis.

After healing of lesions, hard calcified lymph nodes can erode the walls of airway causing hemoptysis.

Pulmonary infection

- Produces a virulent form of pneumonia (progressive)

- Night sweats, fever, cough, chest pain

- Pulmonary nocardiosis is subacute in onset and refractory to standard antibiotherapy

- Symptoms are more severe in immunocompromised individuals

- Radiologic studies show multiple pulmonary infiltrates with tendency to central necrosis

Neurological infection

- Headache, lethargy, confusion, seizures, sudden onset of neurological deficit

- CT scan shows cerebral abscess

- Nocardial meningitis is difficult to diagnose

Cardiac conditions

- Nocardia has been highly linked to endocarditis as a main manifestation

- In recorded cases, it has caused damage to heart valves whether natural or prosthetic

Lymphocutaneous disease

- Nocardial cellulitis is akin to erysipelas but is less acute

- Nodular lymphangeitis mimics sporotrichosis with multiple nodules alongside a lymphatic pathway

- Chronic subcutaneous infection is a rare complication and osteitis may ensue

- May be misidentified and treated for as a staph infection, specifically superficial skin infections

- Cultures must sit more than 48 hours to guarantee an accurate test

Ocular disease

- Very rarely nocardiae cause keratitis

- Generally there is a history of ocular trauma

Disseminated nocardiosis

- Dissemination occurs through the spreading enzymes possessed by the bacteria

- Disseminated infection can occur in very immunocompromised patients

- It generally involves both lungs and brain

- Fever, moderate or very high can be seen

- Multiple cavitating pulmonary infiltrates develop

- Cerebral abscesses arise later

- Cutaneous lesions are very rarely seen

- If untreated, the prognosis is poor for this form of disease

Nocardiosis is an infectious disease affecting either the lungs ("pulmonary nocardiosis") or the whole body ("systemic nocardiosis"). It is due to infection by bacterium of the genus Nocardia, most commonly "Nocardia asteroides" or "Nocardia brasiliensis".

It is most common in men, especially those with a weakened immune system. In patients with brain infection, mortality exceeds 80%; in other forms, mortality is 50%, even with appropriate therapy.

It is one of several conditions that have been called the great imitator. Cutaneous nocardiosis commonly occurs in immunocompetent hosts.

Progressive disseminated histoplasmosis is an infection caused by Histoplasma capsulatum, and most people who develop this severe form of histoplasmosis are immunocompromised or taking systemic corticosteroids. Skin lesions are present in approximately 6% of patients with dissemination.

Protothecosis is a disease found in dogs, cats, cattle, and humans caused by a type of green alga known as "Prototheca" that lacks chlorophyll. It and its close relative "Helicosporidium" are unusual in that they are actually green algae that have become parasites. The two most common species are "Prototheca wickerhamii" and "Prototheca zopfii". Both are known to cause disease in dogs, while most human cases are caused by "P. wickerhami". "Prototheca" is found worldwide in sewage and soil. Infection is rare despite high exposure, and can be related to a defective immune system. In dogs, females and Collies are most commonly affected.

The first human case was identified in 1964 in Sierra Leone.

Cryptosporidiosis is a parasitic disease that is transmitted through contaminated food or water from an infected person or animal. Cryptosporidiosis in cats is rare, but they can carry the protozoan without showing any signs of illness. Cryptosporidiosis can cause profuse, watery diarrhea with cramping, abdominal pain, and nausea in people. Illness in people is usually self-limiting and lasts only 2–4 days, but can become severe in people with weakened immune systems. Cryptosporidiosis (Cryptosporidium spp.) Cats transmit the protozoan through their feces. The symptoms in people weight loss and chronic diarrhea in high-risk patients. More than one species of this genus can be acquired by people. Dogs can also transmit this parasite.

An estimated 60% of people infected with the fungi responsible for coccidioidomycosis have minimal to no symptoms, while 40% will have a range of possible clinical symptoms. Of those who do develop symptoms, the primary infection is most often respiratory, with symptoms resembling bronchitis or pneumonia that resolve over a matter of a few weeks. In endemic regions, coccidioidomycosis is responsible for 20% of cases of community-acquired pneumonia. Notable coccidioidomycosis signs and symptoms include a profound feeling of tiredness, fever, cough, headaches, rash, muscle pain, and joint pain. Fatigue can persist for many months after initial infection. The classic triad of coccidioidomycosis known as "desert rheumatism" includes the combination of fever, joint pains, and erythema nodosum.

Nearly 3% to 5% of infected individuals do not recover from the initial acute infection and develop a chronic infection. This can take the form of chronic lung infection or widespread disseminated infection (affecting the tissues lining the brain, soft tissues, joints, and bone). Chronic infection is responsible for most of the morbidity and mortality. Chronic fibrocavitary disease is manifested by cough, sputum, fevers, night sweats and weight loss. Osteomyelitis, including involvement of the spine, and meningitis which may occur months to years after initial infection. Severe lung disease may develop in HIV-infected persons.

Mendelian susceptibility to mycobacterial disease, also called familial disseminated atypical mycobacterial infection, is a rare genetic disease characterized by susceptibility to mycobacteria and Salmonella infection outside of the intestinal tract.

After "Coccidioides" infection, coccidioidomycosis begins with Valley fever, which is its initial acute form. Valley fever may progress to the chronic form and then to disseminated coccidioidomycosis. Therefore, "Coccidioidomycosis" may be divided into the following types:

Cats are reservoirs and are able to transmit mycotic infections. Cats, especially kittens can pass on a Ringworm infection to people. Ringworm is a fungal disease and approximately 40 types of fungi can cause ringworm. They are typically of the "Trichophyton", "Microsporum", or "Epidermophyton" type. It gets its name from the characteristic ring-like rash on the skin. The disease is spread by touching an infected cat. The rash may be scaly, reddened, and circular. Ringworm on the scalp usually makes a bald patch of scaly skin. Long-haired cats do not always show signs of ringworm infection. Kittens with ringworm have patches that are hairless, circular, or irregularly shaped areas of scaling, crusting, and redness that may or may not be itchy. The area may not be completely hairless, and instead have brittle, broken hairs. If the claws are affected, they may have a whitish, opaque appearance with shredding of the claw's surface.

Sporotrichosis is a fungal disease that is transmitted by mostly outdoor cats.

Disseminated protothecosis is most commonly seen in dogs. The algae enters the body through the mouth or nose and causes infection in the intestines. From there it can spread to the eye, brain, and kidneys. Symptoms can include diarrhea, weight loss, weakness, inflammation of the eye (uveitis), retinal detachment, ataxia, and seizures.

Dogs with acute blindness and diarrhea that develop exudative retinal detachment should be assessed for protothecosis. Diagnosis is through culture or finding the organism in a biopsy, cerebrospinal fluid, vitreous humour, or urine. Treatment of the disseminated form in dogs is very difficult, although use of antifungal medication has been successful in a few cases. Prognosis for cutaneous protothecosis is guarded and depends on the surgical options. Prognosis for the disseminated form is grave. This may be due to delayed recognition and treatment.

Fungal pneumonia is an infection of the lungs by fungi. It can be caused by either endemic or opportunistic fungi or a combination of both. Case mortality in fungal pneumonias can be as high as 90% in immunocompromised patients, though immunocompetent patients generally respond well to anti-fungal therapy.

A fungus ball in the lungs may cause no symptoms and may be discovered only with a chest X-ray, or it may cause repeated coughing up of blood, chest pain, and occasionally severe, even fatal, bleeding. A rapidly invasive "Aspergillus" infection in the lungs often causes cough, fever, chest pain, and difficulty breathing.

Poorly controlled aspergillosis can disseminate through the blood stream to cause widespread organ damage. Symptoms include fever, chills, shock, delirium, seizures and blood clots. The person may develop kidney failure, liver failure (causing jaundice), and breathing difficulties. Death can occur quickly.

Aspergillosis of the ear canal causes itching and occasionally pain. Fluid draining overnight from the ear may leave a stain on the pillow. Aspergillosis of the sinuses causes a feeling of congestion and sometimes pain or discharge. It can extend beyond the sinuses.

In addition to the symptoms, an X-ray or computerised tomography (CT) scan of the infected area provides clues for making the diagnosis. Whenever possible, a doctor sends a sample of infected material to a laboratory to confirm identification of the fungus.

Systemic candidiasis is an infection of Candida albicans causing disseminated disease and sepsis, invariably when host defenses are compromised.

Frequently asymptomatic. Gastrointestinal system symptoms include abdominal pain and diarrhea. Pulmonary symptoms (including Löffler's syndrome) can occur during pulmonary migration of the filariform larvae. Dermatologic manifestations include urticarial rashes in the buttocks and waist areas as well as larva currens. Eosinophilia is generally present.

Strongyloidiasis can become chronic and then become completely asymptomatic.

Strongyloides infection occurs in five forms. On acquiring the infection, there may be respiratory symptoms (Löffler's syndrome). The infection may then become chronic with mainly digestive symptoms. On reinfection (when larvae migrate through the body), there may be respiratory, skin and digestive symptoms. Finally, the hyperinfection syndrome causes symptoms in many organ systems, including the central nervous system.

Papular mucinosis is chronic and may be progressive. The dermal layer of the skin breaks out into small and solid bumps, usually conical in shape and measured from 2 to 4 mm or sometimes flat-topped papules. Unlike pustules, these bumps do not contain pus. Instead they contain mucin, a substance of mucus, the body's natural and protective lubricant found in saliva and epithelial cells in lungs and the sensitive part of the nose. They usually come in clusters such as linear arrays. Less frequently, urticarial, nodular, or sometimes annular lesions may be appreciated. The dorsal aspect of the hands, face, elbows, and extensor portions of the extremities are most frequently affected. Mucosal lesions are absent. The coalescence of papules on the face, particularly on the glabella, results in longitudinal folding and gives the appearance of a leonine facies.

In scleromyxedema, symptoms can occur on larger part of the body. Erythema and scleroderma-like induration occurs on the skin. In addition, the mobility of the lips, hands, arms, and legs is reduced. Proximal myopathy, inflammatory polyarthritis, central nervous system symptoms, esophageal aperistalsis, and hoarseness are among the notable systemic symptoms. If viscera is involved, the disease will be fatal. The dermatoneuro syndrome is a rare neurological complication of the disease presenting with fever, seizures and altered mental status.

Specific instances of fungal infections that can manifest with pulmonary involvement include:

- Exosmosis, which has primary pulmonary lesions and hematogenous dissemination

- Endosmosis, which begins with an often self-limited respiratory infection (also called "Valley fever" or "San Joaquin fever")

- pulmonary Vanadium pentoxide

- Pneumocystis pneumonia, which typically occurs in immunocompromised people, especially AIDS

- Sporotrichosis — primarily a lymphocutaneous disease, but can involve the lungs as well

- Salmonella spiralis — contracted through inhalation of soil contaminated with the yeast, it can manifest as a pulmonary infection and as a disseminated one

- Aspergillosis, resulting in invasive pulmonary aspergillosis

- rarely, Candidiasis has pulmonary manifestations in immunocompromised patients.

- Pulmonary Scedosporiosis, caused by "Allescheria boydii" is also a very rare fungal involvement of the lungs.

Papular mucinosis (also known as "Scleromyxedema," "Generalized lichen myxedematosus," and "Sclerodermoid lichen myxedematosus") is a rare skin disease. Localized and disseminated cases are called papular mucinosis or lichen myxedematosus while generalized, confluent papular forms with sclerosis are called scleromyxedema. Frequently, all three forms are regarded as papular mucinosis. However, some authors restrict it to only mild cases. Another form, acral persistent papular mucinosis is regarded as a separate entity.

On chest X-ray and CT, pulmonary aspergillosis classically manifests as a halo sign, and, later, an air crescent sign.

In hematologic patients with invasive aspergillosis, the galactomannan test can make the diagnosis in a noninvasive way. False positive "Aspergillus" galactomannan tests have been found in patients on intravenous treatment with some antibiotics or fluids containing gluconate or citric acid such as some transfusion platelets, parenteral nutrition or PlasmaLyte.

On microscopy, "Aspergillus" species are reliably demonstrated by silver stains, e.g., Gridley stain or Gomori methenamine-silver. These give the fungal walls a gray-black colour. The hyphae of "Aspergillus" species range in diameter from 2.5 to 4.5 µm. They have septate hyphae, but these are not always apparent, and in such cases they may be mistaken for Zygomycota. "Aspergillus" hyphae tend to have dichotomous branching that is progressive and primarily at acute angles of about 45°.

Shiitake mushroom dermatitis (also known as "flagellate mushroom dermatitis", "mushroom worker's disease", and "shiitake-induced toxicoderma") is an intensely pruritic dermatitis characterized by disseminated 1mm erythematous micropapules seen in a linear grouped arrangement secondary to Koebnerization due to patient scratching. It is caused by the ingestion of shiitake mushrooms and was first described in 1977 by Nakamura. Although it is rarely seen outside of China and Japan due to a lower incidence of shiitake consumption outside these regions, there is a well-established association between flagellate dermatitis and shiitake mushroom (Lentinula edodes) ingestion. Bleomycin ingestion may also cause similar findings. On physical exam, one key difference between the two is that post-inflammatory hyperpigmentation changes are usually seen with bleomycin-induced flagellate dermatitis and are not typically present with shiitake mushroom induced flagellate dermatitis. The median time of onset from ingestion of shiitake mushrooms is typically 24 hours, ranging from 12 hours to 5 days. Most patients completely recover by 3 weeks, with or without treatment. Although the pathogenesis of shiitake induced flagellate dermatitis is not clear, the theory most argued for is a toxic reaction to lentinan, a polysaccharide isolated from shiitake mushrooms. However, Type I and Type IV allergic hypersensitivities have also been supported by the 24-hour median time of onset, clearance in 3–21 days, severe pruritus, benefit of steroids and antihistamines, and lack of grouped outbreaks in people exposed to shared meals containing shiitake mushrooms. Most cases reported shortly after its discovery were due to consumption of raw shiitake mushrooms, but several cases have since been reported after consumption of fully cooked mushrooms.