COCCIDIOIDES (SYSTEMIC MYCOSES)

Question 1

Describe Coccidioides.

Answer 1

• Cause of influenza-like infection in humans called Coccidioidomycosis.
• The disease was also found in dogs, burrows, swine, sheep, horses, monkeys, gorillas, chinchillas, and llamas

Question 2

The animal pathogen of Coccidioides spp.

Answer 2

C. immitis

Question 3

Describe the morphology and staining features of Coccidioides spp.

Answer 3

• Form slender hyphae and spherical bodies (spherules or sporangia) with protoplasmic shoots from the sperules
• Wall is double-contoured, highly refractile and bulging
• Mycelium is rarely observed
• Arthroconidia grow into spherical sporangia with birefringent walls (spherules) containing numerous endospores.

Question 4

What are the growth characteristics of Coccidioides spp.?

Answer 4

• Yeast form is not cultured
• Spherules are seen in lesions
• Grows in simple media over a broad range of temperature
• Hydrolyzes bovine blood
• Develops a brownish discoloration in old culture medium and the growth remains white.

Question 5

What are the reservoirs of Coccidioides spp.?

Answer 5

Soil

Question 6

What are the transmission routes of Coccidioides spp.?

Answer 6

• Inhalation of dust containing spores from mycelial and arthroconidia infected environment

Question 7

Describe the pathogenesis of C. immitis in dogs.

Answer 7

• Coccidioidomycosis
• Disseminated infection but shows negative result on skin tests
• Abscess formation in skin, viscera, heart, eye and genital tract
• Enlargement of glands
• Calcification of infected tissues

Question 8

Describe the pathogenesis of C. immitis in cattle.

Answer 8

• Benign disease that involves only the posterior mediastinal and bronchial lymph nodes
• Enlarge glands
• On post-mortem, lesions are seen in the lungs, submaxillary, retropharyngeal and mesenteric lymph nodes
• Affected glands are enlarged
• Discrete and confluent granulomas in the posterior mediastinal and bronchial lymph nodes

Question 9

Describe the pathogenesis of C. immitis in horses.

Answer 9

• Characterized by severe progressive emaciation
• Moderate anemia
• Pronounced leukocytosis
• Edema of the lower parts of the legs

Question 10

What are the virulence factors of Coccidioides spp.?

Answer 10

1. Coccidioidins
2. Sperulins

Question 11

What are diagnostic methods for Coccidioides spp.?

Answer 11

• Source of samples from animal fluids and tissue sections

Question 12

What are the preferred culture media and substrate of Coccidioides spp.?

Answer 12

• SDA
• Agent identification
• Isolation and purification of coccidioidin
• Complement fixation test
• FAT
• Demonstration of the fungus(H and E, Gomori and methanamine silver stains)
• Exo-antigen test
• Direct mounts and microscopic exams
• Pathogenecity test
• Bacterial culture and isolation
• Coccidioidin test

Question 13

What are the treatment agents for Coccidioides spp.?

Answer 13

1. Amphotericin B injections
2. Ketoconazole
3. Itraconazole