Mannheimia spp Flashcards
Characteristics
Small, facultative anaerobic, non-motile, gram- negative rods or coccobacilli that do not form endospores.
Biochemical test
Oxidase positive
Nitrate reduction positive
Habitat and hosts
Mucosal commensals of the oropharynx and gastrointestinal tract of healthy mammals, birds and reptiles.
Frequent in transported animals
Most important species in sheep and goat
Mannheimia haemolytica
Mannheimia haemolytica
Causes
Shipping fever, pneumonic pasteurellosis
Morbidity and mortality
Mannheimia haemolytica
Habitat
Innocuous inhabitant of the nasal cavity and tonsil
crypts
Mannheimia haemolytica
Susceptible to this disease when ?
stressed (over-crowding, exhaustion, starvation, dehydration, cold temperature)
Mannheimia haemolytica
Source of infection
Organisms shed from the nasal cavity
Mannheimia haemolytica
Virulence factors
Leucotoxin – induces lysis of ruminant leukocytes and platelets
LPS (lipopolysaccharide) – induces haemorrhage, edema, hypoxia, & acute inflammation
Mannheimia haemolytica
main important factors in development of pneumonia in exposed animal:
The challenge dose of Mannheimia haemolytica
The immune status of the host.
Mannheimia haemolytica
Transmission
Inhalation of droplets , direct nose to nose, ingestion of feed contaminated with nasal discharge
Clinical signs of pneumonic pasteurellosis
- depression, anorexia, fever, nasal discharge, soft & moist cough (become apparent 6-10 days after stressful episode)
- dyspnea and open mouth breathing (consolidated lung)
- death due to bronchial obstruction with fibrinous exudates
Diagnosis of pneumonic pasteurellosis
Bacterial isolation from clinical specimens : grow on
blood agar (24 hr incubation), colonies are smooth, grayish, variable β-hemolytic, 1-2 mm in diameter.
