immitis

Immitis refers to Coccidioides immitis, a pathogenic dimorphic fungus that causes coccidioidomycosis, also known as valley fever, in humans and animals. It belongs to the genus Coccidioides, which includes C. immitis and C. posadasii. In the environment, C. immitis grows as a mold that produces arthroconidia; when inhaled, these spores convert to tissue-dwelling endosporulating spherules that release endospores and propagate infection.

Geographic distribution and ecology: Coccidioides immitis is endemic to semiarid regions of the southwestern United States, parts of Mexico and Central and South America. C. posadasii has a broader distribution outside California. Outbreaks are linked to dust events and soil disturbance, with climate and soil conditions influencing spore generation and persistence.

Clinical features: Most infections are asymptomatic or present as mild respiratory illness. Symptomatic disease can resemble pneumonia and may be accompanied by erythema nodosum or multiforme. Chronic pulmonary disease or cavitary lesions can occur. Disseminated disease affects skin, bones, joints, and meninges and is more likely in certain ethnic groups and immunocompromised individuals. Meningitis is a severe form of dissemination.

Diagnosis: Serology using immunodiffusion or complement fixation detects antibodies; antigen testing and PCR can assist diagnosis. Imaging may reveal nodules or cavities. Culturing the organism from clinical specimens requires appropriate biosafety measures due to infectious arthroconidia.

Treatment and prognosis: Many acute infections resolve without antifungal therapy. Moderate to severe, chronic, or disseminated disease is treated with antifungals such as fluconazole or itraconazole; amphotericin B may be used for severe disease. Meningeal involvement often requires prolonged, sometimes lifelong, azole therapy.

Prevention and research: No vaccine exists. Reducing exposure to soil and dust in endemic areas can lower risk. Public health surveillance and research focus on diagnostics, treatments, and ecological factors influencing disease.