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The D1466 variant (also called D212) of infectious bronchitis virus (IBV) was detected for the first time in The Netherlands in the late 1970s as an aetiological factor of problems connected with egg losses, which later was not associated with major disease outbreaks (Davelaar and others 1984; de Wit and others 2011). Subsequent studies have revealed that antigenic and molecular properties of this variant differ significantly from other IBV strains (Kusters and others 1987, 1989). Surprisingly, the only strains clustering in the phylogenetic tree with D1466 variant are Dutch V1397 strain and isolates similar to the North American DE072 and GA98 strains (Lee and Jackwood 2001a, 2001b). The dissimilarity between D1466 variant and the rest of the European strains is also confirmed by protection studies which show that little cross-protection is provided by heterologous vaccines (Cook and others 1999). For more than 40 years from its first description, D1466 variant has been only occasionally detected in Europe, most probably due to its low pathogenicity, but mainly that other IBV types, such as 793-B, 624/I or QX have caused major health problems in chickens (de Wit and others 2011). However, results of a recent molecular survey conducted between 2005 and 2006 indicated increasing problems connected with D1466 genotype in most countries of Western Europe (Worthington and others 2008). In the UK or France, only a few cases of the disease caused by D1466 variant were detected, but in other countries the level of detection showed increasing dynamics. In 2005, the average prevalence of D1466-like viruses in Belgium, The Netherlands and Germany was about 3–5 per cent, but in 2006 the incidence of this variant increased to 7 per cent, 10 per cent and 16 per cent, respectively, of the total IBV detected that year.
In Poland, IBV infections were …