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

ZYGOMYCOSIS 359firmed severe necrogranulomatous rhinitis that went as deep as the palate. Lesionswere also confirmed in the lymph nodes and thorax. Conidiobolus incongruens wasisolated from the nasal lesions, parotid gland, submandibular glands, and the lungs.The most important histopathological change was a severe granulomatous inflammationthat contained small eosinophilic foci of coagulative necrosis. There werefungal hyphae in the center of these foci.To explain an outbreak of this magnitude, the authors assume that the infectionwas influenced by environmental factors. After a rainy winter, grass grew plentifully;it was cut, and the cuttings began to decompose. Additional rain, heat, humidity,and the presence of decomposing plants created conditions favorable to proliferationof the etiologic agent (Carrigan et al., 1992).In dogs and cats, the disease usually affects the gastrointestinal tract and mortalityis very high. Lesions of the stomach or small intestine are accompanied by vomiting,and lesions in the colon are accompanied by diarrhea and tenesmus (Ader, 1979).Source of Infection and Mode of Transmission: Zygomycetes are ubiquitoussaprophytes that produce a large number of spores; they are common inhabitants ofdecomposing organic material and food, and are found in the gastrointestinal tract ofreptiles and amphibians. Humans contract the infection through inhalation, inoculation,and contamination of the skin by spores, and sometimes through ingestion. Thecommon route of entry is the nose, by inhalation of spores. Debilitating diseases,such as diabetes mellitus, and prolonged treatment with immunosuppressants andantibiotics, are important causal factors of mucormycosis. Mucoraceae spores probablydo not germinate in individuals with intact immune systems, judging fromexperimental tests in laboratory animals. However, some cases have been describedin apparently normal people with no known underlying disease. Subcutaneous entomophthoromycosisdue to Basidiobolus develops as a result of direct inoculation bythorns, and the disease caused by Conidiobolus spp. is contracted through inhalation.Entomophthoromycosis generally occurs in healthy individuals with no preexistingdisease.In domestic animals, the digestive route of infection seems to be more importantthan inhalation.Role of Animals in the Epidemiology of the Disease: Humans and animals contractthe infection from a common source in the environment. The infection is nottransmitted from one individual to another (man or animal).Diagnosis: Diagnosis is based on confirmation of the agent’s presence in scrapingsor biopsies of lesions by means of direct microscopic examination or by culture.Zygomycetes in tissue can be identified by their large nonseptate hyphae. The speciesof fungus can only be determined by culture and spore identification (Ader, 1979). Anindirect ELISA test with a homogenate of Rhizopus arrhizus and Rhizomucor pusilluscan be useful for diagnosing mucormycosis. This test was able to detect 33 of 43 casesof mucormycosis. The sensitivity of the test is 81% and the specificity is 94%. It cannotdetermine the genus or the species of the causal agent (Kaufman et al., 1989).Control: Human zygomycosis can be prevented in many cases by proper treatmentof metabolic disorders, especially diabetes mellitus. Prolonged treatment withantibiotics and corticosteroids should be limited to those cases in which it isabsolutely necessary. Animals should not be allowed to consume moldy fodder.