Pathological, Clinicopathological and Molecular Investigations on Chickens Experimentally Infected with Avian Leucosis Virus Type J

Avian leucosis virus type J (ALV-J) causes highly economic losses in the production of meat and egg. This study aimed to investigate the effect of experimental infection of one-day-old chicks with ALV-J strain -local isolateon hemogram, biochemical constituents, ALV-J antibody titer, and histopathology of the internal organs. Detection of ALV-J DNA in the internal organs was also performed using the PCR technique. One hundred and twenty chicks -one day old- were randomly divided into two equal groups. The first group was infected intra-peritoneally with isolated ALV-J strain at a dose of 0.2 ml of log104 embryo infected dose (EID50). The second group was kept as normal control and was inoculated intra-peritoneally with 0.2 ml of sterile saline. After inoculation, all experimental birds were kept under strict daily observation for recording clinical signs and mortality rates. At the 1st, 2nd, 3rd, 4th and 5th month post-infection (mpi), blood and tissue samples were collected from each group for determination of hemogram, serum biochemical parameters, antibody titer, and histopathological and molecular examinations of the internal organs. The infected group showed dullness, ruffled feathers, droppings, loss of appetite, decrease in feed intake and depression. The mortality rate reached to18.3% in the infected group. Macrocytic normochromic anemia, leukocytosis, heterophilia, and lymphocytosis were recorded. Serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase activities, and creatinine and uric acid levels were markedly (P<0.05) increased. Lymphoid and myeloid leucosis in the heart, liver, spleen, and kidneys and also erythroid leucosis in the heart and osteopetrosis were recorded. In conclusion, the experimental infection with ALV-J caused alteration in the hemogram, dysfunction of liver and kidney as well as histopathological lesions in the internal organs and bone of infected chickens. These changes began at the 1st mpi and can help in the early diagnosis of disease.