الفهرس 
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Abstract
This study was carried out to illustrate the pathological and clinicopathological alterations in different organs due to avian leucosis virus type J (ALV-J) infection in naturally and experimentally infected chicken. The study conducted on both meat-type and egg-type chickens.
1. Field study
A total of 28 breeder and layer farms located in 3 governorates (El-Sharkiah, El-Dakahliah, and El-Kaliobiah) in Egypt were examined during 2017-2019. The prevalence of ALV-J infection, clinical signs, and mortality rates were investigated. Immunohistochemical, pathological lesions, ALV-J antibody titer, molecular characterization, and isolation of ALV- J were conducted in both meat-type and egg-type chickens.
The results revealed that:
Clinical signs include weakness, dehydration, and emaciation. The mortality rate ranged from 0.6% to 1.8% per week.
Through ELISA screening of 335 serum samples; 122 samples were positive for ALV-J (36.4%).The positive samples from breeder flocks were 39% while in layer flocks were 33.5%.
Through PCR detection of 93 tissue samples from the liver, spleen, and kidney; 65 samples were positive (69.9%).
Virus isolation on CER; the cells changed to cell rounding and cell aggregation.
Virus Isolation on SPF egg; embryos on the 5th -7th dpi show stunting, curling, dwarfing, anomalies, hemorrhages on the body surface, and an enlarged liver.
Post-morteum examination showed that:
- Liver and spleen: Mostly greatly uniformly enlarged which was a mottled or granular appearance.
- Kidneys: Diffusely infiltrated with small white nodules scattered all over the surface. Occasionally, nephroblastoma was detected.
- Proventriculus: Thickening in proventricular mucosa and in some cases the proventricular mucosa may be hemorrhagic.
- Heart: Cardiomegaly, hydropericardium and some hearts show nodular tumors.
- Ovaries & testes: Nonfunctional ovaries and regressed ovarian follicles. Tests were poorly developed with small nodular growths on the surface.
- Bone: Myelocytomas develop at the costochondral junctions of the ribs, on the inner sternum and inner surface of the pelvis.
Microscopic examination revealed that:
- Liver shows lymphoid, myeloid, and erythroid leucosis in some cases myeloid and lymphoid tumors were detected in the same organ.
- Spleen: lymphoid, myeloid, and reticular cell leucosis were observed
- Kidneys: multifocal neoplastic aggregations of granular myeloid cells in renal tissues. Nephroblastoma also observed.
- Proventriculus and intestine showed Lymphoid and myeloid leucosis while erythroid leucosis observed in the intestine.
- Ovaries: sheets of well-differentiated myeloid cells expand and replace the ovarian stroma. Also, lymphoid leucosis was recorded.
- Testes: focal infiltration of lymphocytes under the tunica albuginea layer of tests.
- Heart: pleomorphic lymphoid and myeloid cells were described in the myocardium.
- Lungs: neoplastic lymphocytes that infiltrate capillary beds of numerous lobules and are causing expansion of interstitial tissue in some cases while myeloid leucosis were observed in other cases.
- Bone marrow & Bone: the proliferation of granulated myelocytes in various bones and in the periosteum of the sternum, ribs, pelvis, and skull. Osteopetrosis in which thickening of the wall and narrowing of the lumen of sternal bone.
Immunohistochemical positive reactivity staining manifests the topographical distribution of the virus in several organs including the spleen, liver, kidney, proventriculus, ovary, oviduct, and lung.
2. Experimental study
One hundred and twenty of one-day-old (SPF) chicks were serologically negative for ALV-J antibody. The chicks were randomly divided into 2 equal groups. First group (infected) was intra-peritoneally (IP) inoculated with 0.2 ml of log104 embryo infected dose (EID50) of locally field isolated ALV-J, while second group (normal control) was inoculated IP with 0.2 ml of PBS. The hematological, and biochemical constituents, ALV-J antibody titer and histopathology of the internal organs were investigated monthly for 5 months post infection (mpi).
The results revealed that:
Clinical signs demonstrated in the infected group, ruffled feathers, loss of appetite, emaciation and depression were recorded. Mortality rate revealed (18.3%) among the experimentally infected chicks.
Macrocytic hypochromic anemia with significant leukocytosis was recorded from the 2nd mpi till the end of the experiment. The differential leukocytic count revealed significant heterophilia and lymphocytosis associated with a decrease in monocytes and eosinophils count.
Serum ALT and AST activities and creatinine and uric acid levels significantly (P<0.01) increased from the 3rd mpi till the end of the experiment. While the ALP activity significantly increased by at the 5th mpi.
On using ELISA test, the ALV-J antibody titer was significantly (P<0.01) increased by the time from the 3rd mpi till the end of the experiment.
Post-morteum findings: In the infected group, diffuse enlargement of liver, spleen, and kidney with small whitish nodules was observed on the liver, spleen, kidneys together with cardiomegaly, and whitish nodules at the heart apex was also seen.
Microscopic examination for the infected group revealed:
- Liver: congestion of hepatic sinusoids and central veins and portal BVs, marked activation of Kupffer cells with the aggregation of some reticular cells between hepatocytes. By the 3rd mpi, aggregations of granulocytic myeloid cells between hepatic tissues were observed.
- Spleen: Pleomorphic lymphoid population around the arterioles which show mitotic activity. By Giemsa stain, myeloid cells were seen with their eosinophilic granules especially on the 3rd mpi.
- Kidney: Neoplastic myelocytes were infiltrating and replacing the renal parenchyma at the 3rd mpi. Also, diffuse granulated myeloid cells were infiltrating the renal parenchyma causing pressure atrophy on the 5th mpi.
- Heart: Focal lymphocytic aggregation between muscle bundles of myocardium was observed which showing pleomorphism by the 3rd mpi. Erythroid leucosis represented by severely dilated and engorged coronary packed with numerous erythroblasts by the 5th.mpi.
- Bones and Bone marrow: acinar structure with cellular hyperplasia and newly formed acini were observed. At the 4th mpi, increasing numbers of granulated myeloid cells. By the end of the experiment at the 5th mpi, osteopetrosis in which thickening of the wall and narrowing of the lumen of sternal bone.
In conclusion, IHC technique is highly sensitive for the detection of the specific antigen in different tissues comparable with PCR. This technique could explain the topographical distribution of the virus in different organs and tissues. Detection of ALV-J specific antibodies in sera of infected chickens helps in the identification of ALV-J infected flocks and may be valuable in monitoring the infection. Hematological and biochemical alterations in combination with histopathological changes confirm the diagnosis of ALV-J. The mixed type of tumors could be observed in the tissue, that’s to say you can detect lymphoid and myeloid leucosis in the same organ or myeloid and erythroid leucosis in the same organ.