Abstract
Since the first reported cases of ducks infected with a previously unknown flavivirus in eastern China in April 2010, the virus, provisionally designated Duck Tembusu Virus (DTMUV), has spread widely in domestic ducks in China and caused significant economic losses to poultry industry. In this study, we examined in detail structural, antigenic, and evolutionary properties of envelope (E) proteins of six DTMUV isolates spanning 2010–2012, each being isolated from individual farms with different geographical locations where disease outbreaks were documented. Structural analysis showed that E proteins of DTMUV and its closely related flavivirus (Japanese Encephalitis Virus) shared a conserved array of predicted functional domains and motifs. Among the six DTMUV strains, mutations were observed only at thirteen amino acid positions across three separate domains of the E protein. Interestingly, these genetic polymorphisms resulted in no detectable change in viral neutralization properties as demonstrated in a serum neutralization assay. Furthermore, phylogenetic analysis of the nucleotide sequences of the E proteins showed that viruses evolved into two distinct genotypes, termed as DTMUV.I and DTMUV.II, with II emerging as the dominant genotype. New findings described here shall give insights into the antigenicity and evolution of this new pathogen and provide guidance for further functional studies of the E protein for which no effective vaccine has yet been developed.
Highlights
In April 2010, there was a severe disease outbreak in duck farms of the major duck-producing regions in eastern China [1]
One 2011 Duck Tembusu Virus (DTMUV) strain was used for this study and the virus was isolated from a diseased duck farm located in Guangxi, one of southernmost provinces in mainland China that shares a border with southeastern Asian countries
It has been reported that the scale of DTMUV-associated epidemics was temporally different [1,2,4,18]
Summary
In April 2010, there was a severe disease outbreak in duck farms of the major duck-producing regions in eastern China [1]. The widespread disease affected both meat and laying ducks. The diseased layer ducks had a significant reduction in egg production ranging from 20% to 60%, even up to 90% in some reported cases. With disease progression, infected ducks developed some nervous system disorders including unsteady standing, falling and quivering. Similar neurological symptoms were observed in meat ducks, especially 20–40 days old ducklings. Recent studies indicated that domestic chickens were susceptible to this emerging disease with similar symptoms [1,2,3,4,5]. The new disease has become one of the most economically important infectious diseases of ducks in China [6]
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