Introduction

• Cause: non-contagious soil-borne infection caused by a dimorphic fungus, Coccidioides spp. Endemic to the Southwestern USA and parts of Central and South America. Mostly affects dogs but all mammalian species can be affected.
• Signs: primarily chronic respiratory signs. Often subclinical. May cause neurological or dermatological signs.
• Diagnosis: clinical examination, hematology, biochemistry, serology, radiography, cytology, histopathology.
• Treatment: antifungal therapy.
• Prognosis: depends on severity of infection.

Pathogenesis

Etiology

• Coccidioides spp: Coccidioides immitis and C. posadasii.

Predisposing factors

General

• Living in endemic area.
• Recent travel to endemic areas.
• Stress and immunosuppression may contribute to clinical disease.

Specific

• Inhalation of fungal spores (arthroconidia) released from the mycelium in the soil, which may be carried on dust particles.

Pathophysiology

• Each inhaled arthroconidium enlarges to form a spherule that contains hundreds of endospores.
• Tissue-invasive spherules rupture to release hundreds to thousands of endospores over 48-72 h.
• The endospores then mature into new endosporulating spherules.
• Localized respiratory tract infection may be seen, but the organism may disseminate through blood and lymphatics.
• Infections may occur in bone, skin and abdominal viscera.
• Abortions accompanied by placentitis, fetal infection and osteomyelitis with or without respiratory signs have also been reported in mammals.
• Recovered animals usually show lifelong immunity.

Timecourse

• Incubation period may be 1-3 weeks.

Epidemiology

• Infection is acquired by inhalation of fungal arthroconidia (single-celled fragments of mycelium) from dust or soil.
• The incidence of infection is highest in late summer and early fall, especially in years following a wet winter. Epidemics occur when rainy periods are followed by drought, which leads to dust storms.
• This infection is rare in exotic pet mammals.

Diagnosis

Treatment

Prevention

Outcomes