VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

MORPHOLOGY

• D. congolensis is Gram positive, non acid fast and aerobic to facultatively anaerobic.
• It is filamentous and branching. Mature filaments are composed of motile, coccal zoospores, in parallel lines, at least two abreast, resulting in a 'tram-track'-like appearance.
• The zoospores are about 1 um in diameter. If the flakes of scab (collected from infections) are treated too roughly, when the smears are made, the filaments will disintegrate and only Gram-positive cocci (zoospores) will be seen.

Life cycle

• Transverse, horizontal and vertical septa form in the immature filaments dividing it into coccal zoospores.
• When mature, these zoospores are motile by polar flagella and are infective.