Wright's stain, 1000x

          Coccidioides immitis is an organism with a limited geographic distribution. In North America, it can be found in the southwestern United States; it is rare to find infections with this organism outside of this endemic region. Clinical cases have been reported for many domestic and wild species. In the arthroconid state, the organism penetrates the host by the respiratory tract and transforms into spherules varying between 20 and 200 mm in diameter (black arrow). The spherules act as germinal centers and from these centers endospores are produced (red arrow). These endospores are sufficiently small to be phagocytized by inflammatory cells of the infected animal (neutrophils and macrophages).  The respiratory infection can be followed by a disseminated infection. When cytology does not allow an etiologic diagnosis, a serological test (based on antigen detection) can be performed.