Characterization of newcastle disease viruses in wild and domestic birds in Luxembourg from 2006 to 2008

Abstract

Newcastle disease virus (NDV) is one of the most important viral diseases of birds. Wild birds constitute a natural reservoir of low-virulence viruses, while poultry are the main reservoir of virulent strains. Exchange of virus between these reservoirs represents a risk for both bird populations. Samples from wild and domestic birds collected between 2006 and 2010 in Luxembourg were analyzed for NDV. Three similar avirulent genotype I strains were found in ducks during consecutive years, suggesting that the virus may have survived and spread locally. However, separate introductions cannot be excluded, because no recent complete F gene sequences of genotype I from other European countries are available. Detection of vaccine-like strains in wild waterbirds suggested the spread of vaccine strains, despite the nonvaccination policy in Luxembourg. Among domestic birds, only one chicken was positive for a genotype II strain differing from the LaSota vaccine and exhibiting a so-far-unrecognized fusion protein cleavage site of predicted low virulence. Three genotype VI strains from pigeons were the only virulent strains found. The circulation of NDV in wild and free-ranging domestic birds warrants continuous surveillance because of increased concern that low-virulence wild-bird viruses could become more virulent in domestic populations.

Fig 1

Geographic distribution of collected samples by municipalities in Luxembourg. The shading corresponds to the number of samples collected per municipality. The numbers indicate the origins of isolates as follows: 1, duck/Luxembourg/26/2006 and pigeon/Luxembourg/119/2006; 2, great cormorant/Luxembourg/2547/2006; 3, chicken/Luxembourg/2871-18/2007; 4, duck/Luxembourg/3785/2007 and duck/Luxembourg/3786/2007; 5, pigeon/Luxembourg/3821-1/2007; 6, mallard/Luxembourg/4178/2008. The strain pigeon/Luxembourg/2657-2/2006 originated from an animal rescued at the animal wildlife shelter in Dudelange (7). Template map © Origine Cadastre: Droits Réservés è l'Etat du Grand-Duché de Luxembourg (2012).

Fig 2

Phylogenetic analysis of partial F gene sequences based on nucleotides 332 to 571. Sequences generated in this study are indicated by the circles (strains presented in Fig. 2 and Fig. 3) and squares (strains presented in Fig. 2 only). Previously published sequences are indicated with their accession numbers. Only bootstrap values of ≥50% are shown. The scale corresponds to number of base substitutions per site.

Fig 3

Phylogenetic analysis of complete F gene sequences (1,662 nt). Symbols are as in Fig. 2. Only bootstrap values of ≥50% are shown. The scale corresponds to number of base substitutions per site.