The Preliminary Research On The Epidemiology And Some Biological Characteristic Of Alvs In Layer Breeders

To inspect imported grand parent layer breeders for the exogenous ALVs'infection status. We chose 3 flocks of grand parent layer breeders and 1 parent layer breeder, the cloaca swabs and sera were collected at different ages on the 45d, 20w, 35w, 45w and 57w. They were tested for p27 antigen detection and antibody. The results indicated that the infection of the exogenous ALVs was widely spread. For the three inspected grand parent layer breeders: the positive rates of p27 antigen vary considerably among different lines, there was no relationship between the p27 detection and feather growth rates. With the increase of age, there is a trend of rising of the positive rate of ALV AB and J subgroup specific antibody and p27 antigen. The positive rates of the antibody and antigen in rooster lines exceeded the hen lines. The twice tests for the parent breeder LSSD03 during the 35 weeks indicated that the antibody positive rate of the exogenous ALVs'infection within 1%, the antibody negtively was in the majority. The p27 antigen positive rate made a great difference among the groups, some as high as 35% of population.Since there was infection of exogenous ALVs in the breeders. To investigate the source of their infection we inspected imported egg-type grandparent breeder chicks for their avian leukosis virus (ALV) infection status, 240 1-day-old chicks were kept and raised in SPF isolators. The cloaca swabs, blood plasmas and sera were collected for 6 times at different ages during about 3 months. They were tested for p27 antigen detection, virus isolation and antibodies. The results indicated that the positive rates of p27 antigen were quite different among 6 varieties of the grandparent breeders. One of them were kept negative for all swab samples, other 5 varieties demonstrated p27 periodically at different tiems and rates in cloaca swabs. There was no relationship between the p27 detection and feather growth rates. One of 36 chicks was transiently positive to ALV-AB antibody at 45d and 2 of 36 chicks were transiently positive to ALV-J antibody at 60d in the variety C. Plasma samples collected at 7 and 21 days of age and inoculated into DF1 cells, no exogenous virus was isolated from all 240 chickes.Sixty chickens from differnet flocks with which the viremia ,p27 antigen and rhe specific antibody for ALVs detected negtively were choosen and divided into four groups, mainlineed with four strains of three different subgroups exogenous ALVs. The cloaca swabs, blood plasmas and sera were collected weekly after inoculation. They were tested for p27 antigen detection, virus isolation and antibodies. The results shows that the viremia of all of the four groups reached a peak level on the 10 week after inoculation. But the viremia maitainance made a great difference among different sudgroups of ALVs. The viremia positive rate reached 92% 10 week after inoculation with the ALV subgroup J isolated from the layer breeders named 66. While the viremia positive rate of the experimental group inoculated with the other subgroups varyied between 46.67% to 60%. The viremia all of the four groups showed transiently positive. The subgroup A was in the 3^rd and 4^th week, subgroup B in the 4^th , 5^th and 6th week; ALV-J subgroup (NX0101) in the 3^rd week while ALV-J(66) in the 4th week after inoculation, during this period the viremia of all the chicken showed negtive. There was difference in the antibody positive response among the four groups: ALV-A and ALV-J(NX0101) showed antibody positive on the third week after inoculation while ALV-B and ALV-J(66) was on the 5^th week. The p27 shedding was peaked, the positive rate reached the peak(25%) on the 12^th week after inoculation to the ALV-A; To ALV-B there was on the 7^th week and it reached to 26.67%; The pattern of the p27 shedding vary greatly between two strains of subgroup J Avian Leukosis Viruses. The peak of the p27 positive rate to NX0101 strain was on the 4^th and 9^th week after inoculation as the same as the layer breeder isolation strain. The different thing was that on the 3^rd week after inoculation there was no p27 positive to the layer breeser isolation strain but the p27 positive rate reached to 26.67%.