Special Veterinary Pathology

Coccidioidomycosis

COCCIDIODOMYCOSIS

Synonym : Coccidioidal granuloma

Definition

• It is a granulomatous disease caused by Coccidioides immitis

Incidence

• It affects man, dog, cattle, sheep, horse and pigs, comparatively benign in animals.

Transmission

• Infection: inhalation of spores, ingestion and cutaneous wounds.
• Fungus on cultures produce mycelia but not in tissue
• Spherules called sporangia (5 to 50 µ in diameter with double contoured wall

Clinical signs

• Horses – Emaciation, oedema of legs, anaemia and leucocytosis
• Dogs – Fever, cough and dyspnoea

Gross lesions

• Lung and lymphnodes showed postmortem lesions
• Lesions: resembles tuberculosis
• Granulomatous nodules with caseous centre and others with calcification
• The lymph node showed foci of suppuration. On section, thick yellow pus may be seen.
• Dogs: Disseminated form- Grayish nodules in the lung,lymph nodes, liver, spleen, bone marrow and meninges

Microscopical lesions

• Granuloma with spherules surrounded by epitheloid cells.
• In cattle, the central part resembles the rosetti of actinomycosis with delimiting acidophil clubs.
• When sporangium ruptures, liberating the young spherules,neutrophils predominatesBut when the spherules mature one, epithelioid cells predominates
• Both exudate and proliferative reactions are seen.
• Organisms can be demonstrated within langhan’s giant cell.
• Special stains with gridley’s stain bring out double contoured wall.

Diagnosis

• Demonstration of the fungus in the lesions
• Intradermal sensitivity test – “coccidioidin”