Gastrointestinal Infections V (24)

Question 1

What are salient features of mycobacterium?

Answer 1

aerobic, non-spore forming, non-motile rods

cytochemically gram-positive

acid-fast (ZN-positive) due to high lipid and mycotic acid in their cell walls

genus includes obligate pathogens, opportunistic pathogens, and saprophytes

grow slowly

resistant to chemical disinfectants and environmental influences but susceptible to pasteurization

Question 2

How do mycobacterium grow? They cause _____

Answer 2

intracellularly

cause granulomatous infections

Question 3

What is the causative agent for tuberculosis?

Answer 3

mycobacterium tuberculosis

Question 4

M. avium complex has main hosts of most avian species except _____

Answer 4

psittacines

Question 5

Mycobacterium are [vulnerable/resistant] to adverse environmental conditions. Why?

Answer 5

resistant - due to their lipid-rich walls

Question 6

How do you identify mycobacterium spp. in the lab?

Answer 6

acid-fast staining (Ziehl-Neelsen)

grow very slowly on solid media

Question 7

T/F: Mycobacterium spp. require safety precautions

Answer 7

TRUE

Question 8

_____ is required for growth for M. avium subsp. paratuberculosis

Answer 8

Mycobactin

Question 9

Mycobactin is required for growth for ______

Answer 9

M. avium subsp. paratuberculosis

Question 10

In identifying mycobacterium, highly reliable and fast molecular techniques such as ____ and 16s rRNA sequencing have been developed

Answer 10

PCR

Question 11

What is the causative agent for Johne’s disease?

Answer 11

mycobacterium avian subsp. paratuberculosis

Question 12

Johne’s disease is also called ______

Answer 12

paratuberculosis

Question 13

What is Johne’s Disease? Who is normally affected?

Answer 13

worldwide, chronic, contagious granulomatous enteritis of mainly ruminants

Question 14

What is Johne’s Disease characterized by?

Answer 14

persistent diarrhea, progressive weight loss, debilitation, and eventually death

Question 15

How do ruminants acquire Johne’s disease? Why?

Answer 15

fecal-oral route

m. avian subsp. paratuberculosis is excreted in large numbers in feces of infected animals and in lower numbers in their colostrum and milk

Question 16

How is m. avium subsp. paratuberculosis introduced in a non-infected herd?

Answer 16

through herd expansion or replacement purchases (via sub clinically infected carriers)

Question 17

A cow had persistent diarrhea and progressive weight loss until finally dying. A Ziehl-Neelsen acid-fast method was used to stain her ileum. What is the causative agent and disease?

Answer 17

mycobacterium avium subsp. paratuberculosis

Question 18

What is the pathogenesis of Johne’s disease? It eventually provokes a _____

Answer 18

infects macrophages in the GI tract and associated lymph nodes

provokes a chronic granulomatous enteritis that interferes with nutrient uptake and processing

Question 19

What are clinical findings of paratuberculosis?

Answer 19

infected animals can appear healthy for months

in cattle, weight loss and diarrhea

progresses and can have ventral and intermandibular edema

Question 20

A cow has ventral and intermandibular edema, weight loss, and diarrhea. How was it infected? Identify pathogenesis, causative agent, and disease

Answer 20

fecal-oral route
infected macrophages in GI tract and associated lymph nodes

provoked a chronic granulomatous enteritis which interferes with nutrient uptake and processing

mycobacterium avium subsp. paratuberculosis

Johne’s disease

Question 21

In sheep and goats, what are the clinical findings for Johne’s disease?

Answer 21

diarrhea may not be seen

Question 22

In dairy cattle and goats with Johne’s disease, _____ may drop

Answer 22

milk production

some animals may just be affected subclinically, with some production losses

Question 23

What are the lesions of Johne’s disease?

Answer 23

thickened and corrugated intestine with enlarged and edematous neighboring lymph nodes

Question 24

Describe the lesions of mucosa of a cow infected by m. avium subsp. paratuberculosis

Answer 24

thickened and corrugated intestine with enlarged and edematous neighboring lymph nodes

Question 25

Describe the lesions that one may have with Johne’s disease

Answer 25

thickened and corrugated intestine with enlarged and edematous neighboring lymph nodes

carcasses emaciated with loss of pericardial and perirenal fat

distal small intestinal wall is diffusely thickened

diffuse granulomatous enteritis

acid-fast organisms may be seen within macrophages

Question 26

Histologically, what is seen of Johne’s disease lesions?

Answer 26

diffuse granulomatous enteritis, characterized by accumulation of epithelioid macrophages and giant cells in the mucosa and submucosa of the gut

Question 27

Acid-fast organisms of Johne’s disease may be seen _____

Answer 27

within macrophages

Question 28

How do you diagnose Johne’s disease?

Answer 28

PCR

Question 29

How do you control and prevent Johne’s disease?

Answer 29

no satisfactory treatment

prevent new infection - colostrum from paraTB-free animals only