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

COCCIDIOIDOMYCOSIS 323and kidneys. The llama seems to be highly susceptible to infection by C. immitis. Itis not known whether there are unapparent or slight infections in this species(Fowler et al., 1992).After man, the dog is the species most affected. In addition to the lungs, granulomatouslesions are found in nearly all organs. The disseminated form of the diseaseis frequent in dogs and the disease advances progressively until death (Timoney etal., 1988).Source of Infection and Mode of Transmission: C. immitis is a soil saprophytein arid and semiarid regions. Its distribution in endemic zones is not uniform. Theinfection is transmitted to man and animals through inhalation of wind-bornearthrospores of the fungus; it occurs more frequently after dust storms. The infectioncan be contracted in the laboratory by inhaling the spores from fungus cultures.Exposure to soil with a high concentration of the agent increases the risk of asymptomatic and severe disease. This was probably the case with two archeologystudents on a dig in southern California (Larsen et al., 1985; Ampel et al., 1989).Those most exposed to contracting the infection are individuals without a historyof the infection who visit or migrate to endemic areas.Coccidioidomycosis is currently increasing in the United States due to significantgrowth in population and tourism in endemic areas.In recent decades, due to the great increase in the use of immunosuppressantdrugs for transplants, oncology, and rheumatology, as well as to AIDS, the severeform of the disease is seen more frequently (Ampel et al., 1989).Role of Animals: The soil is the common source of infection for man and animals.The fungus is not transmitted from one individual to another, because man andother infected animals do not produce arthroconidia, the infecting agent. An exceptionalcase due to aerosolization of endospores occurred during the autopsy of ahorse with disseminated coccidioidomycosis. The veterinarian who performed theautopsy contracted the infection by inhaling the endospores (Kohn et al., 1992).Diagnosis: Diagnosis is based on confirmation of the fungus’s presence by meansof: (1) direct microscopic examination that reveals spherules with endospores insputum, pus, pleural fluid, or gastric juices (treated with a 10% solution of potassiumhydroxide); (2) culture of clinical material; and (3) histopathology. Culturesshould not be prepared in Petri dishes but in closed tubes so as to avoid infection ofthe handler and laboratory personnel. Appropriate biosafety equipment should alsobe used.The skin test using coccidioidin or spherulin (considered to be more sensitive) isvery valuable in epidemiologic studies. It is administered in the same way as tuberculin.The test should be read at 24 and 48 hours. A reaction of 5 mm or more is consideredpositive. This test is very useful for delimiting endemic areas. In infectionsby C. immitis there may be cross-reactions with other fungal antigens, especiallyhistoplasmin. In clinical diagnosis, the intradermal test with a positive result is onlysignificant if the patient had no reaction at the beginning of the illness. In a studycomparing the tests with coccidioidin (prepared from the mycelial phase fungus)and spherulin (parasitic phase fungus) in patients with coccidioidomycosis, onepreparation could not be shown superior to the other for diagnosis. Forty-three percentof the patients reacted positively to both preparations, another 43% reacted