| Avian leukosis(AL) is one kind of neoplastic diseases caused by alpha-retroviral retrovirus avian leukosis virus(ALV) via vertical and horizontal transmission. The main characteristics of AL in field is immune suppression, growth inhibition and multiple tumors, which brought huge economic losses to poultry industry of the world. The poultry industry has been gaining rapid development in Guangdong Province over the past thirty years, but many local chicken strains have been infected with exogenous ALVs is indisputable fact. In order to understand the real infection situation of ALV in yellow feather grandparent roosters of Guangdong local chicken strains, three different breeds of yellow feather roosters were conducted for exogenous ALV etiological investigation. Reference base of AL purification was provided by comparing the result of different samples in ALV detection.In this study, a, b, c three flocks of yellow feather roosters were surveyed for ALV etiology. The cloacal swab, anticoagulated blood sample and semen was collected aseptically and sequentially from each rooster, thus totally 88, 100 and 80 different samples were collected from the above a, b, c breeds respectively. ALV p27 antigen ELISA and DF-1 based virus isolation were used to detect the samples and the results were compared. The results showed that the ALV p27 antigen positive rate of cloacal swabs samples of the a, b, c breed was 76.14%(67/88), 75%(75/100) and 6.25%(4/80) respectively. The virus isolation positive rate of plasma was 60.23%(53/88), 24%(24/100) and 2.50%(2/80) respectively. The virus isolation positive rate of semen was 34.09%(30/88), 11%(11/100) and 0 %(0/80) respectively. Further analysis showed that the higher S/P value of cloacal swab samples, the higher exogenous virus isolation rate of their corresponding plasma and semen. When the ALV p27 antigen ELISA S/P value of cloacal swabs higher than 1.8, the virus isolation rate of plasma virus was 100%(46/46) in the study. In addition, the comparative result of swab and plasma showed that when the S/P value higher than 1.8 or less than 0.048, the ALV p27 antigen positive rate of cloacal swab in accordance with the virus isolation rate of plasma, which indicateed that the test samples appeared small possibility of false negative or false positive in this S/P interval value range in the study. When 0.048?S/P value?0.2, there is 7.30%(6/82) false negative samples, while 50.30%(74/147) false positive samples when the S/P value> 0.2 in the study. We also found that the p27 antigen positive rate of cloacal swabs was higher than the virus isolation rate of plasma, and virus isolation rate of plasma was higher than virus isolation rate of semen in the three strains, but all of which has exceeded the transient national standard of AL purification. The results suggested that combined methods are needed to avoid some “false positives” and “missed” in the ALV purification.Some of the positive plasma samples in the three strains were identified by PCR. There were 6 strains of ALV-J isolates from flock a named JF151022A43XJ?JF151022B5XJ?JF151022B20XJ?JF1510223XJ?JF151031329XJ?JF151031396XJ respectively; 3 isolates of ALV-J from flock b named JF15090634XJ?JF151016100XJ?JF151029112XJ seperately; and 2 ALV-J isolates from flock c named JF201500428 and JF220150327. In those isolates, the genetic difference of gp85 was not obvious and the sequence similarity was 93.6%~100.00%. Compared to the gp85 of HN06, HPRS103, NX0101, SCAU11-H and SCAU11-XG, the similarity was 91.8%~98.1%. It turned out that all the three rooster flocks were infected by exogeous ALVs and all the isolates were ALV-J.The result of this study showed that the role of rooster should not be neglected in eradication program. Single type of sample and simple detection method will easily make some "false positives" and "missed", which will prolong the course in the AL purification. This study provides a reference and scientific basis for AL purification in the local chicken breeds of Guangdong area. |
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