ANIMAL HEALTH ^Ringworm/ Other Fungus Diseases By David K. Chesier Disease caused by fungal valleys, while coccidioidomy- organisms (mycosis) oc- cosis is common in the desert curs throughout the world. Southwest—^but any of these There are about 100,000 spe- can be seen elsewhere. Other cies of fungi, with less than fungi are found throughout 200 of them involved in fun- the country, but are more gal infections of animals or common in hot, humid envi- humans. ronments. Fungus diseases vary The importance of fungal greatly in clinical signs, inci- diseases in animals must be dence and geographic distribu- kept in mind. "Ringworm" tion. Skin infections such as usually is not serious to the "ringworm," found worldwide, animal; however, it is impor- are the most common. Sys- tant to diagnose and treat it temic (internal) fungal dis- properly because the animal eases are less common overall, can be a source of human in- but in specific localized areas fection. a disease of this group could Systemic fungal diseases be the most serious and com- are not directly contagious mon disease seen, from animals to humans, but Histoplasmosis and blas- can be fatal to the infected an- tomycosis are common in the imal or require long and ex- Ohio and Mississippi river pensive treatment. Some fungi are opportunistic. They are common in the environment David K. Chester is Professor of but infect animals or humans Medicine, Department of Small only under unusual circum- Animal Medicine & Surgery, Col- stances. lege of Veterinary Medicine, Texas Fungal diseases often look A&M University, College Station. like other diseases, which may 472 Dogs and Cats ANIMAL HEALTH result in misdiagnosis and ex- ears or feet, or reddened, scaly pensive, ineffective or harmful skin in areas of broken hair. treatment. In severe cases, scales and crusts may accumulate and 'Ringworm' Infections the skin becomes thickened Three fungal organisms, Mi- and itchy. crosporum cants, Microsporum gypseum, and Trichophyton Dogs iUiore Affected mentagrophytes cause nearly Lesions in dogs usually are all the dermatophyte infec- more severe. The hair is bro- tions (^'ringworm") in dogs ken or gone, papules (small and cats. swellings), scales, crusts, and The cat is the preferred redness are more prominent host for Microsporum canis. signs. As the disease spreads This organism will easily in- from one hair follicle to an- fect dogs and people. Infec- other, a circular pattern of tions result from direct con- skin redness develops around tact with infected animals or a healing center. This looks infected hairs or skin. somewhat like a worm under Microsporum gypseum the skin, resulting in the term normally grows in the soil. ''ringworm." Animals develop the disease Dermatophytosis is diag- by digging or otherwise con- nosed by finding typical skin tacting the infected soil. lesions, a history suggesting Many species of animals, exposure to the organisms or especially wild rodents, carry contagiousness, and labora- Trichophyton mentagrophytes. tory evaluation. Laboratory Their burrows are seeded with confirmation of the disease is the organism and many dogs especially important since the and cats develop "ringworm'' lesions alone can look like so by contact with these rodents many other diseases. or their burrows. The most reliable labora- Lesions caused by derma- tory test is fungal culture. tophytes are confined to the Broken hairs or scrapings skin or haircoat and appear from the skin are placed on similar regardless of which or- appropriate culture media and ganism causes them. allowed to grow in a dark, Cat lesions often are so moist area. The fungi will mild they go unnoticed for usually grow within 4 to 10 years. Lesions may consist of days, but cultures generally broken hairs around the face, are held 3 weeks before de- Ringworm, Other Fungus Diseases 473 ANIMAL HEALTH daring them negative. The or- fection and spread to other an- ganism can be identified by imals. staining and microscopic ex- amination. Systemic Infections An ultraviolet (Black or Three diseases generally are Wood's) light may be used to classified as systemic fungal help identify some Microspo- infections because they can in- rum canis infections. volve any or all of the body Skin scrapings may be systems. They are: Blastomy- cleared of debris with sodium cosis, caused by Blastomyces hydroxide and examined un- dermatitidis, histoplasmosis, aer a iTLÎcroscope for spores of caused by Histoplasma capsu- fungi. Experienced personnel latum, and coccidioidomycosiSj can identify fungal diseases caused by Coccidioides immi- with this technique/but iden- tis. tification of the specific orga- All these organisms are nism usually is not possible. found in the soil in endemic Treatment, Dermatophyte a-Yeas. Blastomyces and Histo- treatment aims are: Cure the plasma prefermoist soil en- infected animal and prevent riched with bird or bat drop- reinfection or infection of pings and Coccidioides prefers others. hot, dry, alkaline soils. All Hair in and around the three diseases result from in- animal's lesion should be haling infective spores from clipped off and disposed of. Lo- soil. They all grow in the body cal treatment with baths, in a noncontagious yeast form. dips, creams or lotions con- Many animals and hu- taining antifungal agents are mans living in endemic areas then prescribed. Oral medica- have had these diseases, de- tions such as griseofulvin or veloped immunity and re- ketoconazole may also be covered without the problem used. being realized. The diseases Treatment needs to con- start with respiratory signs tinue 6 weeks or longer in such as cough, rapid breath- most animals. ing, or pneumonia and fever. Isolating infected ani- When these diseases become mals, cleaning and/or disin- severe or chronic, the result fecting the premises, and may be weight loss, loss of ap- washing well after treating petite, inactivity and even infected animals are impor- death. tant in preventing human in- Each of the diseases has 474 Dogs and Cats ANIMAL HEALTH signs more specific to that dis- It is becoming common ease. Severe diarrhea is com- practice to use both drugs in mon with histoplasmosis but early treatment and then con- not with blastomycosis or coc- tinue with ketoconazole alone cidioidomycosis. Nodular after a few weeks. draining skin lesions are com- Direct infection of hu- mon with blastomycosis but mans from infected animals uncommon in the other two has not been reported. Hu- diseases. Coccidioidomycosis mans can become infected frequently affects the bones^— from the same source as their resulting in swellings, lame- animals. ness and fractures—while that is much less common with the Subcutaneous Types other two diseases. These fungus diseases are so Laboratory confirmation named because the main clini- of these diseases is needed cal sign is a nodule or abscess even though the diagnosis just under the skin. The orga- may be suggested by history nism usually is introduced and physical findings. The into the body from bite most reliable finding is locat- wounds, rose thorns or other ing the organism in dis- foreign bodies, or accidents. charges or body ñuids by cy- The three most common dis- tology or in the tissue by eases in this group are: Sporo- biopsy. Blood tests (serology) trichosis, phycomycosis and may be helpful but are not as mycetoma. reliable as finding the orga- Lesions of the diseases nisms. are nodules or tumor-like Treatment of animals for masses on the skin. They may these diseases requires have openings which drain months of therapy with expen- reddish or yellowish fluid or sive and potentially toxic which exude granules. Besides drugs. Amphotericin-B is con- the skin lesions, sporotrichosis sidered the most effective may become systemic and af- treatment. It must be given fect any of the organ systems. intravenously and often Frequently phycomycosis in- causes kidney damage. volves only the gastrointes- Ketoconazole is a newer, tinal tract of the dog, result- less toxic drug that can be ing in vomiting, diarrhea, and given orally but has not been rapid weight loss. as effective in acute illness The diseases are diag- and is quite expensive. nosed by finding the causative Ringworm, Other Fungus Diseases 475 organisms in infected tissue. only when the animal's im- Sporotrichosis can be mune system is compromised. cured by several months of Immune suppression can be a therapy with sodium iodide if result of drug therapy with the disease has not become cortisone type steroids or anti- systemic. Sodium iodide may cancer drugs, and immunosup- also be used to treat the sys- pressive diseases. temic disease but results are The most common symp- poor. Mycetoma and phycomy- toms associated with these cosis lesions can be cured if diseases are respiratory they can be surgically re- (coughing, sneezing, nasal dis- moved. When that is not pos- charge) with cryptococcosis sible, treatment usually is not and Aspergillus infections, successful. and ear infections with Can- With the exception of spo- dida, Pityrosporum and Asper- rotrichosis, humans are not gillus. likely to get these diseases Some animals become se- from animals. If infected ma- verely debilitated. terial gets in a wound, any of The diseases are treated them have the potential to with various drugs but most cause disease. important is to take steps to improve the animal's general Other Infections health. These diseases are not A number of fungal organisms considered contagious to hu- are present in the environ- mans. ment which can cause disease 476 Dogs and Cats .