In cattle, regular T.B. testing is very much important in farm.

T.B. is caused by Mycobacterium bovis in bovine.

But how this process is work?


Mechanism of action:-

Causative agent is complex and is engulf by macrophage while immune response.

This is express by MHC-2 molecule and it trigger TH-1 cell(by IL-12 secreted by macrophage)

Th-1 cell secrete IFN-gamma instead of IL-4 and IL-5(which secreted by TH-2 cell and help to humoral response.)

IFN-gamma is potent activator of macrophage and enhance its activity.

It also form epithelioid cell and giant cell.

If we inject T.B. agent to intra dermal then it showing delayed type hypersensitivity.

TH-1 cell is circulated in blood, lymph and take rest in lymph node.

It showing response against injected causative agent if patient suffer from T.B. or it has memory cell of that agent.

After injection of causative agent, TH-1 cell activate immune response and visible response at dermal is occur. 

It take time about 48 hour.

Process of T.B test in bovine

  • Take a tuberculin syringe
  • 0.1ml PPD is require for testing
  • Save the area of injection
  • 0.1ml PPD inject in intra dermal
  • Result is seen after 48-72 hour.
  • Measure the thickness of injected area 72 hour

Result of T.B. test

Positive:- Injected area are swollen and painfull and thickness is more than threshold after 48-72 hour

Negative:- No any visible reaction is seen at injected area.