Protective Efficacy of Recombinant Turkey Herpes Virus (rHVT-H5) and Inactivated H5N1 Vaccines in Commercial Mulard Ducks against the Highly Pathogenic Avian Influenza (HPAI) H5N1 Clade 2.2.1 Virus.

Walid H Kilany,Samy M Mohammed,Abdullah Salim,Folorunso Oludayo Fasina,Mohammed K Hassan,Yilma M Jobre,Gwenaelle Dauphin,Juan Lubroth,Azhar G Shalaby,Marwa Safwat,Olubunmi G Fasanmi

doi:10.1371/journal.pone.0156747

Abstract

In Egypt, ducks kept for commercial purposes constitute the second highest poultry population, at 150 million ducks/year. Hence, ducks play an important role in the introduction and transmission of avian influenza (AI) in the Egyptian poultry population. Attempts to control outbreaks include the use of vaccines, which have varying levels of efficacy and failure. To date, the effects of vaccine efficacy has rarely been determined in ducks. In this study, we evaluated the protective efficacy of a live recombinant vector vaccine based on a turkey Herpes Virus (HVT) expressing the H5 gene from a clade 2.2 H5N1 HPAIV strain (A/Swan/Hungary/499/2006) (rHVT-H5) and a bivalent inactivated H5N1 vaccine prepared from clade 2.2.1 and 2.2.1.1 H5N1 seeds in Mulard ducks. A 0.3ml/dose subcutaneous injection of rHVT-H5 vaccine was administered to one-day-old ducklings (D1) and another 0.5ml/dose subcutaneous injection of the inactivated MEFLUVAC was administered at 7 days (D7). Four separate challenge experiments were conducted at Days 21, 28, 35 and 42, in which all the vaccinated ducks were challenged with 106EID50/duck of H5N1 HPAI virus (A/chicken/Egypt/128s/2012(H5N1) (clade 2.2.1) via intranasal inoculation. Maternal-derived antibody regression and post-vaccination antibody immune responses were monitored weekly. Ducks vaccinated at 21, 28, 35 and 42 days with the rHVT-H5 and MEFLUVAC vaccines were protected against mortality (80%, 80%, 90% and 90%) and (50%, 70%, 80% and 90%) respectively, against challenges with the H5N1 HPAI virus. The amount of viral shedding and shedding rates were lower in the rHVT-H5 vaccine groups than in the MEFLUVAC groups only in the first two challenge experiments. However, the non-vaccinated groups shed significantly more of the virus than the vaccinated groups. Both rHVT-H5 and MEFLUVAC provide early protection, and rHVT-H5 vaccine in particular provides protection against HPAI challenge.

Highlights

Egypt is one of five countries where the highly pathogenic avian influenza (HPAI) H5N1 has become endemic
In the winter of 2014–2015, Egypt recorded an epizootic of HPAI H5N1 virus, because of the emergence of a new but dominant H5N1 virus cluster [17]
Whereas the first four measures are perceived as the classical approach to the disease and have gained prominence worldwide, vaccination against avian influenza H5N1 is still hotly debated and its implementation is considered on a country-by-country basis only

Summary

Introduction

Egypt is one of five countries where the highly pathogenic avian influenza (HPAI) H5N1 has become endemic. There are vast numbers of domestic ducks in Egypt in the household sector, a recognized source of infection and transmission of the HPAI H5N1 virus to poultry and humans [3,4,5,6,7]. There is insufficient information on the effectiveness of HPAI H5N1 vaccination in domestic duck species to guide disease control programs. Because the ducks play a central role in the epidemiology of HPAI H5N1 in Egypt, the present study was conducted to fill the knowledge gap about the rHVT-H5 vaccine and to assess the effectiveness of HPAI H5N1 vaccine in domestic water fowl. The study was designed to monitor the post-vaccination serological response to a single dose of the rHVT-H5 vaccine, compared to a dose of an inactivated H5N1 reverse genetic vaccine based on clade 2.2.1 and 2.2.1.1 Egyptian seed strain (MEFLUVAC), in protecting domestic Mulard ducks from challenges with HPAI H5N1 clade 2.2.1 viruses from Egypt

Methods

Results

Conclusion