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Coccidioidomycosis

Issue Description
Coccidioidomycosis is a fungal disease caused by Coccidioides immitis, and less frequently, by Coccidioides posadasii.1It was first recognized as a human disease in Argentina in 1892, and was first reported as a disease of animals in 1918, with a case of bovine infection. Since then, it has been found in both wild and domestic animals, including deer, tigers, mice, rats, squirrels, gorillas, monkeys, dogs, cats, sheep, cattle, horses, and reptiles.


Symptoms
In cases of mild respiratory infection, dogs may present with a dry harsh cough, resulting from tracheobronchial lymphadenomegaly or diffuse interstitial pulmonary disease, or with a moist productive cough, if the alveoli are affected. If the pulmonary disease is advanced, generalized pneumonia and more severe respiratory signs may be present. Fever, weight loss, and inappetance are commonly seen with the respiratory form. In cases of systemic infection, the clinical signs are referable to the sites of dissemination. Dissemination may occur with or without respiratory signs. In dogs, spread to the bones of the appendicular skeleton is common, and lameness with or without painful bone swellings may be present. Other common sites of dissemination include the lymph nodes, skin, liver, spleen, central nervous system and, less frequently, the eye and myocardium. Spread to these sites may be accompanied by generalized lymphadenomegaly, ulcerated nodules or draining tracts in the skin, cranial or paraspinal hyperesthesia, seizures, ocular abnormalities, or signs of left-sided heart failure due to restrictive pericarditis, respectively. Rarely, direct injection of spores through the skin can result in a localized, self-limiting granulomatous lesion.

Diagnosis
Diagnosis of coccidioidomycosis may be difficult due to the chronic nature of the disease and the spectrum of nonspecific clinical signs that could also be seen with other infectious, inflammatory, neoplastic, or immune-mediated conditions. Clinical signs, serum biochemistry analysis, radiographs and other advanced imaging modalities, and serology can be helpful in making a diagnosis, but organism identification by cytology, histopathology, or culture is the only way to make a definitive diagnosis. The diagnosis is further complicated by the high portion of the population that sustains infection without clinical disease; therefore, presence of the organism may not mean that it is directly responsible for clinical signs observed.

Treatment
Due to the high variability in severity and extent of disease, no standard treatment protocol has been defined. Some patients may recover without any treatment, while others may die after aggressive medical treatment. Therapy may be avoided in patients that have only mild respiratory signs. In patients with more severe pulmonary or systemic disease, long-term systemic antifungal therapy is required. The azole antifungals (ketoconazole, itraconazole, and fluconazole) are the most widely prescribed drugs in veterinary medicine, with amphotericin B used less frequently. The prognosis is highly variable, with an estimated overall recovery rate of 60%. Patients with mild respiratory signs usually make a full recovery, while those with disseminated disease may die or require medical treatment for the rest of their lives. Some dogs, and many cats, have relapses of disease when therapy is discontinued after apparent clinical resolution.

Dogs
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