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Gross and microscopic lesions PowerPoint PPT Presentation


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Gross and microscopic lesions. Characteristic, but not pathognomonic Insensitive diagnostic method (19% positive animals lack lesions) Could be difficult to differentiate from other pneumonias (Pasteurella, Haemophilus). Seroconversion to Different Agents vs Average Lesion Score. Serology.

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Gross and microscopic lesions

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Gross and microscopic lesions

  • Characteristic, but not pathognomonic

  • Insensitive diagnostic method (19% positive animals lack lesions)

  • Could be difficult to differentiate from other pneumonias (Pasteurella, Haemophilus)


Seroconversion to Different Agents vs Average Lesion Score


Serology

  • ELISA-based tests currently available

  • Tween-ELISA

  • Commercial Tween-ELISA

  • IDDEX ELISA

  • Dako ELISA


Tween-ELISAS

  • Antigen is a composite of membrane proteins

  • Excellent when prepared in-house

  • Some dispute as to whether it cross reacts with flocculare

  • Commercial tests give some false positives


IDDEX ELISA

  • Becoming a very common test

  • Very high sensitivity

  • Specificity can be a problem:false positives

  • In negative herd monitoring, positives must be confirmed with the Dako test


Dako ELISA

  • Targets a specific protein: blocking ELISA

  • Appears to be as sensitive and more specific than other tests

  • Expense is a concern


One site continuous flow


One site AI/AO


3 Site / Multisite


PCR

  • Rapid and specific

  • Does not depend on viable bacteria

  • Can be done in live (lung lavages) and dead animals

  • works well from necropsy and lung lavages ……….. application in the field?


Nested PCR

  • May be done in live animals

  • Good correlation with serology

  • It is not quantitative

    • Should be used at the population level


Nested PCR Interpretation


N-PCR Interpretation

  • Nasal Mycoplasma are found only when shed from tracheobronchial sites

  • Early Infection: PCR positive, probably due to non-attaching and dead Mycoplasmas

  • Late Infection: Positives due to active shedding

  • Mid-term Infection: Negatives due to attached Mycoplasma not being carried to nose


The future

  • One-step PCR …….. as a diagnostic profiling test

    • More rapid

    • least false positives

    • N-PCR…use for monitoring clean herds


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