[A] 1.61 General pathogenesis of tuberculosis

Question 1

The stages during TB were described by…

Answer 1

• Ranke: In humans
• Nieberle: In animals

Question 2

Give the stages of pathogenesis of TB

Answer 2

• Primary phase
  
  • Phase of reinfection
• Postprimary phase
• Breakdown phase

Question 3

Answer 3

• Lung: +++
• GI-tract: +
• Liver: -

Question 4

Answer 4

• Lung: +
• GI-tract: +
• Liver: ++

Question 5

Answer 5

• Lung: ++++
• GI-tract:
• Liver:

Question 6

Answer 6

• Lung:
• GI-tract: ++++
• Liver:

Question 7

Answer 7

• Lung:
• GI-tract: ++++
• Liver:

Question 8

Answer 8

• Lung: ++
• GI-tract: ++
• Liver:

Question 9

Answer 9

• Lung:
• GI-tract: ++++
• Liver:

Question 17

Unusual sites of the primary process in some species: Cattle

Answer 17

• Genital organs
• Skin
• Udder

Question 18

Unusual sites of the primary process in some species: Goat & Sheep

Answer 18

GI tract

Question 19

Unusual sites of the primary process in some species: Horse & swine

Answer 19

Lung

Question 20

What is shown

Answer 20

Complete primary complex on the lung

Question 21

Unusual sites of the primary process in some species: Swine, dog, cat

Answer 21

Skin

Question 22

Cornet rule

Answer 22

• In case of TB, there is a lesion in the lymph node
• There is no primary TB lesion without pathological changes in the lymph nodes

Question 23

The primary complex

Answer 23

1. Infection
2. Primary process
3. Lesions in the regional lymph node

Question 24

The primary complex: Varieties

Answer 24

• Complete
• Non-complete

Question 25

Complete primary complex

Answer 25

• Lesion on the site of the port of entry
• Lesion in the regional lymph node

Question 26

Draw the complete pathogenesis of TB

Answer 26

Question 27

Non-complete primary complex

Answer 27

• Sometimes no lesion on the site of the port of entry
• But there is a lesion in the regional lymph node

Question 28

The primary process following infection…

Answer 28

• Predominantly exudative - In both organs it develops
• Because the host meets the pathogen for the first time
• and there is not seroconversion, no defence is evolved

Question 30

Progress of the primary complex: possible routes

Answer 30

• Complete healing
• Reaches an inactive quiescent state
• Early generalisation

Question 31

Progress of the primary complex: Complete healing

Answer 31

1. The pathogens are eliminated
2. Lesion is absorbed
3. Lesion is replaced by connective tissue (scar)

In case of new infection:

• Process starts all over again
• Phase of reinfection

Question 32

Progress of the primary complex: Inactive quiescent state

Answer 32

1. The nodule is demarcated with special tuberculotic granulation tissue
2. Pathogens remain infectious in the nodule
3. Constant antigen stimulus reaches the organism
4. Immunity permanently exists
5. Pathogens can get out any time
6. The process flushes → Exacerbation

Question 33

Progress of the primary complex: Early generalisation

Answer 33

• Pathogens get into the circulation
• Infect the organism and metastatise via:
  
  • Haematogenous
  • Lympho-haematogenous
  • Retrograde lymphogenous routes
• Result:
  
  • Distant tuberculotic lesions in different organs

Question 34

Give the forms of generalisation

Answer 34

• Acute: Multiple, tiny, miliary nodules
• Protracted (extended): Tuberculotic nodules with different size and age

Question 36

TB: Primary phase

Answer 36

• Infection
• Development of the primary process

Question 37

TB: Local process

Answer 37

Either:

• Healing
  
  • with the elimination of bacteria
• Becomes inactive
  
  • Demarcation, but bacteria can survive
• Enter the circulation
  
  • Early generalisation develops

Question 38

When does immunity of TB develop?

Answer 38

During the progression of the primary complex

Question 39

Which structured are formed during early generalisation?

Answer 39

Either tubercles or proliferative nodules are formed

Question 40

TB Early generalisation: What happens during this phase

Answer 40

• Bacteria can re-enter the circulation several times
• Fresher and older lesions can be found next to each other
• Regional lymph nodes are affected

Question 41

In most species, TB ends in the phase of…

Answer 41

Early generalisation

• Most die in this phase
• Except for cattle
  
  • Reach inactive phase (which can exacerbate (flush) at any time)
  • Continues to Chronic TB in organs (via postprimary phase)

Question 42

Chronic TB in organs

Answer 42

“Isolate TB”

Can develop due to:

1. Inactive primary complex
2. Inactive early generalisation
3. Exogenous superinfection

Question 43

Chronic TB in organs: Why does no generalisation occur?

Answer 43

The animal has antibodies against the pathogen

• But - The process spreads intra-canalicularly inside an organ
  
  • In the lungs - from acini to acini, from lobules to lobules
• Expectorated content gets to the GI tract (distant metastasis)

Acinous & Acinonodosus TB

• No fresh lesions in the lymh nodes

Question 44

Postprimary phase:

Answer 44

Chronic TB in organs & Processes leading to this stage

Causes:

• Immunosuppression
• Mycobacteria overwhelm the organism
• Inactive process exacerbation

Question 45

TB: Breakdown phase

Answer 45

• Pathogens spread
• Late generalisation develops
• Lymph nodes are also affected
• Chronic TB in organs becomes acute
  
  • ​Extended exudative lesions develop
• Increased intra-canalicular spreading
  
  • Galloping acinonodosous TB (lungs)

Question 46

Summarise the phases of TB

Answer 46

1. Primary phase
2. Postprimary phase
3. Breakdown phase