zoonoses and communicable diseases common to ... - PAHO/WHO

ZYGOMYCOSIS 357Occurrence in Animals: It occurs sporadically in many animal species, such asdomestic and wild mammals (including marine mammals), birds, reptiles, amphibians,and fish. There was a significant epizootic outbreak in New South Wales andQueensland, Australia, affecting 52 sheep farms; 700 sheep died in three months. Thecausal agent was Conidiobolus incongruens of the order Entomophthorales (Carriganet al., 1992).The Disease in Man: The agents of mucormycoses are potential pathogens thatare classified as opportunistic, since they invade the tissues of patients debilitated byother diseases or treated for a long time with antibiotics or corticosteroids. About40% of the cases have been associated with diabetes mellitus. In contrast, in Africaand Asia entomophthoromycoses occur in individuals without histories of preexistingillness (Bittencourt et al., 1982).The mucormycoses are caused by fungi of the genera Absidia, Mucor, Rhizopus,Cunninghamella, Rhizomucor, and several others. The infection begins in the nasalmucosa and paranasal sinuses, where the fungi may multiply rapidly and spread tothe eye sockets, meninges, and brain. The clinical forms caused by these fungi arerhinocerebral, pulmonary, gastrointestinal, disseminated, cutaneous, and subcutaneousmucormycoses. The rhinocerebral form appears mainly in diabetes mellituspatients with acidosis and in leukemia patients with prolonged neutropenia. Patientshave fever, facial pain, and headache. As rhinocerebral mucormycosis progresses,there may be loss of vision, ptosis, and pupillary dilatation. This form of the diseaseis highly fatal. Patients with a malignant blood disease and those receiving immunosuppressantsprimarily suffer from pulmonary or disseminated mucormycoses and,less frequently, from the rhinocerebral form. The gastrointestinal form has occurredin a few cases in malnourished children and in adult patients with advanced malnutrition;it is generally diagnosed postmortem. The cutaneous and subcutaneous formmay be due to deep burns, injections, and application of contaminated bandages.Mucormycosis is characterized by vascular occlusion with fungal hyphae, thrombosis,and necrosis.Localized mucormycosis may disseminate (disseminated mucormycosis) to variousorgans and systems. The underlying diseases are generally leukemia, solid neoplasias,chronic renal deficiency (dialysis treatment with deferoxamine seems topredispose the patient to mucormycosis, particularly to Rhisopus spp.), hepatic cirrhosis,organ transplants (particularly bone marrow transplants), and diabetes. Thelargest group of disseminated mucormycoses involves cancer patients (51% of 185cases analyzed) (Ingram et al., 1989).Treatment consists of controlling the underlying disease, controlling hyperglycemiaand acidosis in diabetics, and reducing immunosuppressant use in othercases. Surgical intervention and systemic administration of amphotericin B yieldedfavorable results in pulmonary and rhinocerebral mucormycosis when diagnosisoccurred early. In primary cutaneous mucormycosis, débridement and topical treatmentwith amphotericin B are indicated. Generally, the earlier the infection isdetected, the smaller the amount of dead tissue that will have to be removed and thegreater the chances for avoiding major tissue damage (Sugar, 1990).Treatment of entomophthoromycosis consists primarily of surgical excision of thesubcutaneous nodules (Basidiobolus) or corrective surgery (Conidiobolus) of thenose and other parts of the face. It is advisable at the same time to treat the patient