Field effectiveness of highly pathogenic avian influenza H5N1 vaccination in commercial layers in Indonesia.

Simson Tarigan,Esmaeil Ebrahimie,Widya Asmara,Peter A Durr,Risa Indriani,Jagoda Ignjatovic,Michael Haryadi Wibowo,Sumarningsih Sumarningsih,Sidna Artanto,Syafrison Idris,Mark A Stevenson,Yongchang Cao

doi:10.1371/journal.pone.0190947

Abstract

Although vaccination of poultry for control of highly pathogenic avian influenza virus (HPAIV) H5N1 has been practiced during the last decade in several countries, its effectiveness under field conditions remains largely unquantified. Effective HPAI vaccination is however essential in preventing incursions, silent infections and generation of new H5N1 antigenic variants. The objective of this study was to asses the level and duration of vaccine induced immunity in commercial layers in Indonesia. Titres of H5N1 haemagglutination inhibition (HI) antibodies were followed in individual birds from sixteen flocks, age 18–68 week old (wo). The study revealed that H5N1 vaccination had highly variable outcome, including vaccination failures, and was largely ineffective in providing long lasting protective immunity. Flocks were vaccinated with seven different vaccines, administer at various times that could be grouped into three regimes: In regime A, flocks (n = 8) were vaccinated two or three times before 19 wo; in regime B (n = 2), two times before and once after 19 wo; and in regime C (n = 6) three to four times before and two to three times after 19 wo. HI titres in regime C birds were significantly higher during the entire observation period in comparison to titres of regime A or B birds, which also differed significantly from each other. The HI titres of individual birds in each flock differed significantly from birds in other flocks, indicating that the effectiveness of field vaccination was highly variable and farm related. Protective HI titres of >4log2, were present in the majority of flocks at 18 wo, declined thereafter at variable rate and only two regime C flocks had protective HI titres at 68 wo. Laboratory challenge with HPAIV H5N1 of birds from regime A and C flocks confirmed that protective immunity differed significantly between flocks vaccinated by these two regimes. The study revealed that effectiveness of the currently applied H5N1 vaccination could be improved and measures to achieve this are discussed.

Highlights

Following the incursion of highly pathogenic avian influenza (HPAI) H5N1 virus into Indonesia in 2003, the disease spread rapidly throughout most of the country wherein it has become endemic [1]
The results showed that HPAI vaccination had highly variable outcome and did not provide sufficiently long protective immunity in the majority of flocks
From the data obtained during the initial visit, eight layer farms in West Java (WJ) and eight in District of Yogyakarta (DIY) were selected for the study based on the following criteria: (i) owners were willing to participate in a nine-month long study and allowed tagging of individual birds; and (ii), farms were representative of the Sector with respect to farm sizes, vaccines used, number of vaccination and husbandry practices

Summary

Introduction

Following the incursion of highly pathogenic avian influenza (HPAI) H5N1 virus into Indonesia in 2003, the disease spread rapidly throughout most of the country wherein it has become endemic [1]. All isolates belonged to subclade 2.1.1, of which the strain A/chicken/Legok/2003 H5N1was used for production of a vaccine in 2005 [7, 8, 14, 15]. By 2008 antigenic variants have emerged that belonged to subclades 2.1.2 and 2.1.3 of which A/chicken/wj/Pwt-Wij/2006 (Pwt) H5N1was developed into a vaccine since A/chicken/Legok/2003-based vaccine did not protect against Pwt challenge [8]. A new H5N1 variant A/duck/Sukoharjo/BBVW1428-9/2012 (Skh) has emerged that belongs to a new subclade of H5N1 2.3.2.1 [16]

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