VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

DIAGNOSIS

Specimens to be collected

• It includes faeces and blood from live animals, intestinal contents and tissue lesions from dead animals, abomasal contents from aborted fetuses and parenchymatous organs from septicaemic conditions.

Diagnosis based on

• Symptoms and lesions
• Isolation and identification of the organism - If the organism is less, initially it is enriched in peptone water and then inoculated in selective enrichment broth.
• After incubation for 48 hours they are streaked onto selective enriched media.
• The samples used are aborted fetus, feces, blood, milk, egg and visceral organs.
• Agglutination test: In horses the O agglutinin titre of 1/1000 or more is considered positive.
• Presence of agglutinin titre against H antigen indicates active infection.
• In cattle a titre of 1 in 40 against O antigen and l in 320 against H antigen is considered positive.
• In poultry a titre of l in 50 & l in 25 is indicative of active infection.
• (Note: The agglutinin titre will vary with different areas for positive cases) (Click here for visual)

• Whole blood agglutination test: 1 drop of colored or plain pullorum antigen is mixed with 1 drop of blood and allowed for 2 minutes. In positive cases there will be clumps.
• Tube agglutination test: In this test the sample serum is diluted serially to which 0.5 ml of constant amount of antigen is added and kept at 37°C in a water bath overnight.
• Agglutinations in dilutions at a titre of 1 in 40 indicates a positive test.