Previous infection with virulent strains of Newcastle disease virus reduces highly pathogenic avian influenza virus replication, disease, and mortality in chickens.

Mar Costa-Hurtado,David E Swayne,Erica Spackman,Claudio L Afonso,Ra Mi Cha,Eric Shepherd,Patti J Miller,Diane Smith,Mary J Pantin-Jackwood,Darrell R Kapczynski,David L Suarez

doi:10.1186/s13567-015-0237-5

Abstract

Highly pathogenic avian influenza virus (HPAIV) and Newcastle disease virus (NDV) are two of the most important viruses affecting poultry worldwide and produce co-infections especially in areas of the world where both viruses are endemic; but little is known about the interactions between these two viruses. The objective of this study was to determine if co-infection with NDV affects HPAIV replication in chickens. Only infections with virulent NDV strains (mesogenic Pigeon/1984 or velogenic CA/2002), and not a lentogenic NDV strain (LaSota), interfered with the replication of HPAIV A/chicken/Queretaro/14588-19/95 (H5N2) when the H5N2 was given at a high dose (106.9 EID50) two days after the NDV inoculation, but despite this interference, mortality was still observed. However, chickens infected with the less virulent mesogenic NDV Pigeon/1984 strain three days prior to being infected with a lower dose (105.3–5.5 EID50) of the same or a different HPAIV, A/chicken/Jalisco/CPA-12283-12/2012 (H7N3), had reduced HPAIV replication and increased survival rates. In conclusion, previous infection of chickens with virulent NDV strains can reduce HPAIV replication, and consequently disease and mortality. This interference depends on the titer of the viruses used, the virulence of the NDV, and the timing of the infections. The information obtained from these studies helps to understand the possible interactions and outcomes of infection (disease and virus shedding) when HPAIV and NDV co-infect chickens in the field.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0237-5) contains supplementary material, which is available to authorized users.

Highlights

Avian influenza virus (AIV) and Newcastle disease virus (NDV) affect poultry worldwide and cause important economic losses [1]
Our results showed that the severity of the disease caused by Highly pathogenic avian influenza virus (HPAIV), the number of birds shedding virus and the titers of virus shed can be reduced by previous infection with virulent strains of NDV if given 2–3 days before HPAIV challenge
In study 1, there were no differences in mortality rates in groups that received HPAIV alone and sequentially and simultaneously infected groups, but increased mean death times (MDT’s) were observed in groups co-infected with lNDV, mNDV and low dose of vNDV

Summary

Introduction

Avian influenza virus (AIV) and Newcastle disease virus (NDV) affect poultry worldwide and cause important economic losses [1]. AIVs are type A Orthomyxoviruses and are classified as low pathogenicity (LP) or high pathogenicity (HP) viruses based on their virulence in chickens and the presence of multiple basic amino acids at the cleavage site of the hemagglutinin precursor protein [2]. NDVs vary in the type and severity of the disease they produce, and different pathotypes, based on their virulence in chickens and principally determined by the sequences surrounding the protease cleavage site of the fusion protein, have been described in poultry [3]. Velogenic and mesogenic viruses are classified as virulent NDV, the cause of Newcastle disease (ND), whereas lentogenic viruses are the low virulence NDV widely used as vaccines [3]. The intracerebral pathogenicity index (ICPI) in day-old chicks is used to differentiate

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