Appraisal of Three Commercial Inactivated Avian Influenza Vaccines Efficacy Against Challenge with Egyptian Duck-Origin Clade 2.3.4.4b H5N8 in Commercial Broiler Chickens | ||
| Journal of Current Veterinary Research | ||
| Volume 6, Issue 1, April 2024, Pages 102-125 PDF (1.67 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jcvr.2024.352706 | ||
| Authors | ||
| Amira Hamdy* ; Abdel-Sattar Arafa; Alaa Gaballa; Hesham Sultan | ||
| Abstract | ||
| The highly pathogenic avian influenza (HPAI) H5N8 virus belonging to clade 2.3.4.4b was detected in Egypt during 2016, which is one of the few countries depends on vaccination as a main control strategy. This study was conducted to assess the efficacy of three different commercial inactivated AI vaccines of different clades (clade 1, clade 2.3.4.4b and (Re-6 & Re-8)) in commercial broiler chickens against HPAI H5N8 clade 2.3.4.4b.The clinical protection percent was 67%, 80% and 87% in G1 (clade 1), G2 (clade 2.3.4.4b), and G3 (Re-6 & Re-8), respectively. The lowest mean antibody titer was recorded in G1 which exhibited unsatisfactory level of immune response. Also, Antisera raised against clade 1 vaccine showed minimal reactivity with clade 2.3.4.4b and Re-6&Re8antigens suggesting poor cross-protection. This was reflected on the antigenic relatedness (R- value) which was low (11.3%) indicating major antigenic difference. Samples were collected for examination of histopathological changes from thymus, trachea, spleen, bursa of Fabricius, lung, and cerebrum. Only mild cerebrum lesions were found in all challenged groups indicating reduced neurotropism. In lymphoid tissues, moderate to severe lesion score were detected. This impairment effect on some bird immune organs highlight the immunosuppressive effect of the virus, which can appear in the vaccinated exposed birds to HPAI virus. It is recommended to update the vaccine seed strains to be closely related to the circulating field strains to obtain better protection levels. Also, continuous evaluation of the validated AI vaccines against recent field strains is substantial. | ||
| Keywords | ||
| Clade 2.3.4.4b; Histopathology; H5N8; HPAIV and Vaccine efficacy | ||
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