Lymphocytic depletion of bursa of Fabricius and thymus in chickens inoculated with Escherichia coli

Specific-pathogen-free 10-week-old chickens were inoculated via the air sac with Escherichia coli and showed lymphocytic depletion of bursa of Fabricius and thymus. In experiment I, chickens were necropsied at 12 and 24 hours, 2, 3, and 5 days after inoculation. At 12 hours after inoculation there was lymphocytic depletion in the medulla of lymphoid follicles of the bursa. At 24 hours after inoculation there was lymphocytic depletion also in the cortex of follicles and edema in interfollicular interstitium and follicular medulla. At 2 and 3 days after inoculation there were more marked lymphocytic depletion in medulla and cortex, and fibrosis in interfollicular interstitium. Partial repopulation of follicles with lymphocytes was seen at 5 days after inoculation. In the thymus, lymphocytic depletion occurred in the cortex. At 12 hours after inoculation, lymphocytic necrosis increased in number more than that of control chickens. The width of the cortex and medulla decreased. At 24 hours after inoculation, lymphocytic necrosis increased further. At 2 to 5 days after inoculation, the boundary between the cortex and medulla of lobules was obscure and cellular elements of the cortex and medulla were mingled. In experiment II, chickens were necropsied as in experiment I and also at 8 and 14 days after inoculation. The relative weights of the bursa and thymus reduced rapidly to minimal relative weights at 8 days after inoculation. At 14 days after inoculation, both bursa and thymus had normal relative weights and histological structures. These findings indicate that E. coli infection may induce transient lymphocytic depletion of lymphoid tissues in the chicken.     

Cryptosporidiosis of the bursa of Fabricius of chickens.

Light-microscope and electron-microscope studies of a coccidial organism found in the bursa of Fabricius from 3 chickens clearly established the parasite as belonging to the family Cryptosporiidae. Hyperplasia and heterophil infiltration were associated with the presence of organisms attached to the microvillus border of epithelial cells lining the plicae of the bursa of Fabricius. Although there were no clinical signs or gross lesions common to the 3 cases described, all had similar histologic lesions in the epithelium lining the bursa of Fabricius.     

Developmental process of Cryptosporidium in the intestine and bursa of Fabricius of chickens.

The developmental process of a Cryptosporidium isolated in Japan in the chicken intestine was investigated by scanning (SEM) and transmission electron microscopies (TEM). The parasites were detected in the ileum, cecum, colon, cloaca and bursa of Fabricius (BF). The intensity of infection tended to peak later in the BF than ileum. Trophozoites and schizonts were detected in all the portions of intestine, and were dominant in the developmental stages. Although macrogamonts were the secondary dominant stage, they were absent in the ileum and cecum at 60 hr postinoculation (PI). A few microgamonts were detected in the ileum at 36 hr PI and in the BF on day 19 PI. Oocysts were observed in the ileum at 48 hr PI and in the BF on day 19 PI.     

Pathogenesis of duck plague in the bursa of Fabricius, thymus, and spleen.

White Pekin ducks were inoculated orally with duck plague virus and killed at 24-hour intervals after inoculation. Spleen, thymus, and bursa of Fabricius were collected and examined by light, fluorescent, and electron microscopy. Necrosis of lymphocytes occurred in the bursa of Fabricius, thymus, splenic periarteriolar lymphoid sheath (T lymphocytes), and splenic germinal centers (B lymphocytes). Viral nucleocapsids were present in the karyoplasm of lymphocytes, but these cells necrotized before virions were formed. Periarteriolar reticular sheath cells and sinusoidal lining cells in the spleen, epithelial cells in Hassall's corpuscle of the thymus, epithelial cells between the cortex and medulla of the follicles in the bursa of Fabricius, and macrophages in all 3 tissues contained nucleocapsids in the nuclei and virions in cytoplasmic vacuoles before necrosis occurred.     

Histochemical and histological evaluations of the effects of high incubation temperature on embryonic development of thymus and bursa of Fabricius in broiler chickens

1.?The effects of experimentally induced heat-stress on the embryonic development of bursa of Fabricius and thymus of the chicken were investigated by means of histological and enzyme histochemical methods.

2.?In the experiments, 250 fertile eggs of the Ross 308 broiler strain were divided into two groups. The control eggs were maintained under optimal conditions (37?8°C and 65 ± 2% relative humidity, RH) during the whole incubation period. Heat stressed eggs were maintained under normal conditions (37?8°C and 65 ± 2% RH) until the 10th d of incubation and then exposed continuously (24 h per d) to high temperature (38?8°C and 65 ± 2% RH). Blood and tissue samples were taken from 10 animals of each group at d 13, 15, 18 and 21 of incubation and at d 2, 4 and 7 post-hatch. Tissue samples were processed for enzyme histochemical methods in addition to routine histological techniques.

3.?The results revealed that egg temperatures were higher than incubator air temperature. Long-term heat-stress (40?1–40?6°C egg temperature) retarded development of thymus and bursa of Fabricius. Peripheral blood ACP-ase and ANAE-positive lymphocyte levels of heat-stressed animals were lower than in the controls.

4.?These results give some morphological evidence for immunosuppression induced by high temperature exposure during the embryonic development. Temperature distribution and air circulation in incubator should be questioned in the case of lower broiler flock immunity.     

Histologic characterization of the involuting bursa of Fabricius in single-comb white Leghorn chickens

Bursas from specific-pathogen-free white leghorn chickens of both sexes were examined at several intervals from hatching to 28 weeks of age. No histologic alterations other than scattered atrophic or cystic follicles were observed through 20 weeks. Obvious involution, first noted at 24 weeks, was in early stages in females and quite advanced in males. Involution was essentially complete by 26 weeks, and only cicatrized vestiges of bursas were present at 28 weeks of age. Gross manifestations included bursal atrophy, variable yellowish discoloration of the mucosa, and matting or total loss of identity of the mucosal plicae. Histologic characteristics of involution are summarized by the following approximate sequence: atrophy and exfoliation of plica epithelium; subepithelial stromal fibrosis; fusion and ultimate collapse of plicae; liquefactive necrosis of first medullary then cortical elements of follicles, which seemed to progress from basal to apical portions of the plicae; progressive proliferation of stromal connective tissue and infiltration of macrophages into areas occupied by necrotic follicles; and, finally, complete fibrous organization of luminal debris, leaving a firm nodule formed by a contracted muscularis surrounding the cicatrized remains of the mucosa.     

Action of herbicide "Atrazine" on thymus and bursa in chickens

Changes were induced in the central lymphatic organs of chicken which had been given 150 ppm "Atrazin" in their rations over 21 days, beginning with the third day of age. The substance did not produce toxic phenomena. Thymus and bursa fabricii weights went up in parallel with the glycogen levels of those organs, after 15 days of feeding. Normalisation occurred on the 21st day of treatment and was more conspicuous on the thymus than on the bursa.     

Involution of bursa cloacalis (Fabricii) and thymus in Cyclosporin A-treated chickens

Fifty-day-old Arbor Acres chickens received a daily oral dose of 30 mg/kg Cyclosporin A for 21 consecutive days. This treatment induced the striking morphological changes in the bursa cloacalis (Fabricii). The number of bursal follicles did not change, but they were markedly decreased in size. The pars lymphoreticularis was collapsed and contained smaller accumulations of lymphocytes. The pars lymphoepithelialis was almost totally devoid of lymphocytes and it was composed of an empty network of epithelial cells. Interfollicular epithelium, follicle-associated epithelium, basement-membrane-associated epithelium and bursal epithelial cytoreticulum were not changed. The thymus also displayed substantial structural changes, whereby the thymic medulla was strongly reduced in size.     

Relationship between delayed onset of egg production and involution of the bursa of Fabricius in White Leghorn chickens

The relationship between delayed onset of oviposition and involution of the bursa of Fabricius is described. Chickens studied were 26 weeks of age and had not come into production. The bursae of nonlaying chickens were compared with those of age-matched chickens that had laid the first egg 1, 9 to 11, or 24 days before. The bursae from the nonlaying chickens were similar in weight and morphology to the functional bursae of immature pullets. Bursae of laying chickens, even on the day of the first egg, were markedly involuted. Age of the chicken was not a factor in determining bursal involution. The onset of egg production was directly related to bursal involution.