Histophilus

Question 1

General characteristics

Answer 1

Separated from other species based on capnophilia, yellow pigment, indole production

• does not require V or X factors
• requires complex-nutrient rich medium
• isolated on yeast-blood agar, incubated in 10% CO2 at 37 C

Question 2

BRD

Answer 2

In association with M. haemolytica and/or P. multocida or alone
- pneumonia, suppurative bronchopneumonia, or fibrinous pleuropneumonia

Question 3

What are 3 bacterium responsible for bovine respiratory disease?

Answer 3

• P. multocida (type A)
• M. haemolytica
• H. somni

Question 4

TME

Answer 4

Thrombotic meningoencephalitis

• caused by H. somni
• high fever, infarcts in brain and cerebellum, depression, lateral recumbency, closed eyes

Question 5

Other symptoms of H. somni

Answer 5

• septicemia
• arthritis
• abortion
• mastitis

Question 6

H. somni in ovine

Answer 6

Respiratory and mammary infections, occasionally septicemia

Question 7

Virulence factors

Answer 7

• nonencapsulated, but LOS undergoes phase variation
• immunoglobulin binding proteins on its surface that bind to Fc regions of bovine Ig = protection from host complement
• adheres to endothelial cells = contraction, collagen exposure, platelet adhesion, thrombus formation
• survives in phagocytic cells