The recent outbreak of avian leukosis virus subgroup J in Chinese local
chickens, 2019
Abstract
Avian leukemia caused by avian leukosis virus (ALV) is one of the most
severe diseases endangering poultry health. When the eradication
measures performed in commercial broilers and layers have achieved
excellent results, ALV in some local chickens has gradually attracted
extentive attention. Since late 2018, following the re-outbreak of ALV-J
in white feather broilers in China, AL-like symptoms also suddenly broke
out in some local flocks, leading to great economic losses. In this
study, a systematic epidemiological survey was carried out in eight
local chicken flocks in Jiangxi Province, China, and 71 strains were
finally isolated from 560 samples, while the env sequences of them were
successfully sequenced. All of those new isolates belong to subgroup J
but they have totally different molecular features and were very
different from the strains that emerged in white feature broilers
recently, with some strains being highly consistent with those
previously isolated from commercial broilers, layers and other flocks or
even isolated from USA and Russian, suggesting these local chickens have
been acted as reservoirs to accumulate various ALV strains for a long
time. More seriously, phylogenetic analysis shows that there were also
many novel strains emerging and in a separate evolutionary branch,
indicating several new mutated ALVs are being bred in local chickens.
Besides, ALV strains isolated in this study can be further divided into
ten groups, while there were more or less groups in different chickens,
revealing that ALV may cross propagate in those flocks. The above
analysis explains the complex background and future evolution trend of
ALV in Chinese local chickens, providing theoretical support for the
establishment of corresponding prevention and control measures.