1 │Introduction
Avian leukosis (AL), inducing malignant or benign tumorigenic diseases
by avian leukosis virus (ALV), has caused immense economic losses all
over the world in the poultry industry since its emergence(Payne &
Nair, 2012; Weiss & Vogt, 2011). ALVs were divided into 11 different
subgroups (designated A to K) based on cross neutralization and gp85
sequences(Dong et al., 2015). Among those, avian leukosis virus subgroup
J (ALV-J) is the most prevalent subgroup in chickens and exhibits
increasing pathogenicity and stronger vertical transmission ability in
recent years (Li et al., 2016; Payne, Howes, Gillespie, & Smith, 1992;
Venugopal, Howes, Flannery, & Payne, 2000). ALV-J infection used to be
a common problem in poultry industry during 2003–2010, when its
widespread causing the myelocytoma of broilers and haemangioma of
layers(Cui, Du, Zhang, & Silva, 2003; Lai et al., 2011; Li et al.,
2018; Li et al., 2013; Pan et al., 2012) . Because of the widespread
distribution of the ALV-J strains, together with the less organized
nature of the poultry industry especially among the local breeds of
chickens, control and eradication of ALV in China remain a major
challenge. Since 2018, a more tumorigenic ALV-J strain has appeared in
the imported broiler breeders in China, inducing severe osteomas in keel
and ribs, causing a massive pandemic, and hence becoming a major avian
health concern. Therefore, many domestic farms have started
self-checking for ALV infection.
Rubin and his colleagues defined four serological classes of susceptible
birds: viraemia, no antibody (V+A−); no viraemia, with antibody (V−A+);
viraemia, with antibody (V+A+); and no viraemia, no antibody
(V−A−)(Payne & Nair, 2012; Rubin, Fanshier, Cornelius, & Hughes,
1962). Yet the researchers did not elaborate on the ALV infection status
of male semen or the role of males in the transmission of ALV. During
another study, Li found that roosters could spread ALV-J to hens by
insemination and cause vertical transmission(Li et al., 2017).
Therefore, roosters may be selected for freedom from Avian leukosis
virus by ELISA tests of cloacal swabs or semen sampling, as well as
virus isolation. However, the accuracy of these detection methods
remains to be defined.
In this study, it was discovered ALV-J infection re-emerged in Hy-line
brown roosters in recent years. Moreover, the hens were infectecd by
insemination, and virus can be transmitted vertically to the breeding
eggs. Several infection states of ALV-J in roosters were clarified and
the reliability of different methods for detecting samples of males were
compared. All those data may provide more detailed basis for the
eradication of ALV.