02/12/2024
Immune Monitoring and Vaccine Success through Hemagglutination Inhibition in poultry
Hemagglutination Inhibition (HI) test is as a critical tool evaluates antibody levels against viruses like Avian Influenza, Newcastle Disease, and Egg Drop Syndrome (EDS). This test works by measuring the ability of antibodies to prevent hemagglutination, a process where viruses cause red blood cells to clump together. When antibodies are present, they block this interaction, preventing agglutination. The strength of this inhibition reflects the immunity in the flock, with higher titers indicating stronger immunity.
The antibody titer derived from the HI test is expressed in Log2 values, which is the logarithmic scale base 2. This helps normalize antibody titers for easier comparison and interpretation.
Key insights include:
✅ HI Test: The HI test helps evaluate vaccine efficacy, identify natural infections, and monitor immunity levels over time. However, interpreting the results of this test requires considering other important factors, such as:
✅ Vaccination History: A flock’s previous exposure to vaccines and the timing of vaccinations significantly influence antibody levels and immune responses.
✅ Environmental Conditions: Temperature, humidity, air quality, and stress factors such as overcrowding or improper handling can affect how effectively birds respond to vaccines and pathogens.
✅ Management Practices: Nutritional status, disease history, and flock management practices, including sanitation and biosecurity measures, play a crucial role in overall flock immunity and the accuracy of HI test results.
✅ Vaccine Quality: Ensuring proper vaccine storage, handling, and administration is essential for successful vaccination. If vaccines are improperly stored or administered, antibody levels may not rise as expected, which could lead to misinterpretation of HI test results.
✴ Interpreting HI Results:
Low titers (≤ 4 Log2): Indicate inadequate immunity, possibly due to poor vaccine response, improper vaccine administration, or lack of previous exposure to the virus.
Moderate titers (5-8 Log2): Suggest acceptable immunity, but may require additional booster vaccinations or improvements in flock.
High titers (≥ 9 Log2): Reflect strong immunity, which may indicate successful vaccination or natural exposure to the virus.
By combining Hemagglutination Inhibition results with detailed vaccination history, environmental factors, and management practices, and ensuring a representative sample size, poultry producers can make informed decisions about the health status of their flocks, improve vaccination strategies, and ensure optimal productivity and disease prevention. To ensure accurate results and a more precise assessment of immunity, it is recommended to use complementary methods like PCR or ELISA.
Reference: IDEXX
