Poultry pancreas is a highly innervated and vascular organ which plays crucial role in maintaining health and optimal growth of poultry through its digestive enzymes and hormones. Any interference in normal functioning of pancreas, either due to damage of nerves such as vagus nerve in disease conditions like pneumonia, polyserositis, egg peritonitis, ascites etc., or due to pathogen, which may invade pancreas in generalized disease conditions like colisepticemia, lymphoid leucosis, brooder pneumonia, Ranikhet Disease (RD), Infectious Bursal Disease (IBD), Infectious Bronchitis (IB) etc. through ascending or descending infections, may result into significant effect on growth performance of birds. Direct spread of pathogen is further facilitated by non-compartmentalized nature of avian viscera.

In view of ever growing demand for broiler meat and eggs, there is tremendous pressure on poultry sector to enhance production, which has made it a breeding place for genesis of various diseases due to failure of scientific management, lack of optimal balanced nutrition, biosecurity breaches leading to incidence of all kinds of infectious and non-infectious diseases and vaccine failures. Significant population of birds show poor body weight gain or rundown condition. Pancreatic dysfunction may in such cases constitute an important underlying contributory factor.

Despite pancreas being such a vital organ, there is paucity of literature reporting correlation between pancreatic pathology and disease conditions. No report seems available, which highlights the degree of pancreatic pathology in different disease conditions. Diseases of exocrine pancreas in pet, exotic and wild birds¹ and feature of necrotic changes in poultry pancreas has been reviewed earlier^2,3. Present study has explored and evaluated the extent of pancreatic pathology in different infectious, nutritional, toxic or metabolic diseases of poultry.

The present study was conducted on the dead birds (different chicken varieties) of any age, sex or breed, which were brought for postmortem examination to Department of Veterinary Pathology, College of Veterinary Science and Animal Husbandry, Birsa Agricultural University, Ranchi during period from December 2017 to November 2018.

Each organ was examined critically for presence of gross lesions. Special emphasis was given on examination of pancreas both in-situ along with duodenum as well as after separating it from duodenum. The change in color, consistency, appearance, size and structural defects were recorded. Pathological, bacteriological or serological (Affinitech antibody ELISA kits for RD, IBD and X-OVO Flockscreen antibody ELISA Kit for IB) examination was carried out for confirmation of the disease condition wherever required.

For histopathological examination, pancreatic tissue was collected from the areas where gross changes were most distinct, care was taken to include the normal part of organ also. The pancreatic tissue was collected in length as well as cross section to get best possible histopathological details. The collected tissues were processed for preparation of 4–5 μ thick pancreatic section and stained with Ehrlich’s haematoxylin and eosin stain⁴. To study histochemical details, Periodic Acid Scruff (PAS) staining was performed for zymogen granules in acinar cells of exocrine pancreas and Mallory’s Trichrome staining (Crooke-Russell Modification) was carried out for collagen fiber in the diseased pancreatic tissue using standard staining technique⁵.

In the present study, post mortem was performed on 3796 birds out of which 22.23% (844) birds showed definite pancreatic pathology. Gross pancreatic pathology in decreasing order of frequency is presented in table 1. Highest incidence of pancreatic involvement was observed in IBD (94.74%). The major gross pathological findings in decreasing order of frequency were bleached appearance (36.97%), congestion (36.97%), mottled appearance with multifocal necrotic lesions (29.50%), pancreatic deformity (15.17%), atrophy (4.15%), and hypertrophy (2.61%).

In majority of cases bleached appearance was seen independently in pancreas (Fig 1). Congestion was not observed in atrophied pancreas. Concomitant development of pancreatic deformity and mild mottling due to multifocal necrosis was also sometimes observed (Fig 2). Mottled pancreas was an important gross pathological finding. These focal changes were either embedded in the parenchyma or showed discrete nodular swelling (Fig 3).

Pancreatic deformity or misshapen pancreas was observed in several birds. Pancreatic deformity was most consistently seen in grower birds as compared to chick, starter and adult birds. A very wide range of pancreatic deformity was observed in the diseased birds. These deformities always occurred in conjunction with deformities of duodenal loop. The direction of pancreatic deformity was exactly followed by duodenal loop giving duodeno-pancreatic loop a distorted appearance (Fig 4). The nature of pancreatic deformity ranged from simple bending, curving, folding, single twisting, multiple twisting, coiling and wavy presentation of duodenopancreatic complex. These changes were seen mostly at the tip of the pancreas. However, twisting, lateral deviation and bending were also observed at the base or mid duodeno-pancreatic segment.

In extreme pancreatic atrophy, as seen in cystaden-ocarcinoma, island of pancreatic tissue was found in the coiled and fused duodenal loop. Pancreas with atrophic changes always appeared pale or bleached with occasional multifocal necrotic lesions. Pancreatic hyperplasia was most commonly seen in young chicks. These pancreases were either pale or bleached in appearance. The gross changes of diseased pancreas mentioned, occurred either as individual lesion or as a mix of multiple lesions.

Microscopic abnormalities observed in the pancreas of birds suffering from different disease conditions and the variations observed in histopathological changes in these disease conditions are presented in table 2. Interstitial and periductular fibrosis were most frequently seen in diseased pancreas. It was characterized by proliferation of fibrous connective tissue in the pancreatic parenchyma. The degree and severity of fibrosis was variable in different disease conditions. It ranged from mild interstitial fibrosis to more advanced cases, where significantly thick band of connective tissue was observed in the intercellular or peri-acinar region (Fig 5). This makes the lobular pattern of pancreas prominent. In many cases, significant periductular fibrosis was found adjacent to exocrine pancreatic tissue. These changes often lead to considerably thick band of connective tissue forming prominent encroachment into the surrounding pancreatic parenchyma. In extreme cases of fibrosis, fibrous and collagenous tissue completely invaded the pancreas and created round island like lobular patern of pancreatic parenchyma. These trapped pancreatic cells showed necrotic changes or were completely destroyed, leaving behind tissue debris. Staining of the pancreas suspected for fibrosis with Mallory Trichrome stain, prominently displayed fibrosis in the interstitial, interlobular and periductular space (Fig 6).

In several cases, the acinar cells showed dissociation / individualization, with disruption of acinar pattern of exocrine pancreas. These changes were seen diffusely throughout the parenchyma, often associated with fibrosis in the interstitial or inter lobular space, necrosis with infiltration of inflammatory cells, apoptosis and vacuolar degeneration of the acinar cells. Multifocal Necrosis in pancreatic parenchyma of birds showed disruption of acinar patern and individualization. Sometimes exocrine pancreas showed coagulation necrosis characterized by cytoplasmic acidophilia of degenerating cells with pyknotic nuclei. On few occasions, subcapsular necrosis was observed. Proliferation of fibrous connective tissue in and around necrotic zone has also been recorded (Fig 7).

Vacuolar degeneration was also found to vary from few vacuoles in the microscopic field to almost 70–80% acinar cells. Often round or oval residual bodies were found in the vacuoles. These residual bodies are suggestive of apoptotic cells and were detectable both intracellularly and extracellularly (Fig 8). Increased zymogen granules were observed both with haematoxylin and eosin (H & E) stain as well as periodic acid (PAS) stain. In these conditions the apical portion of acinar cells were filled with zymogen granules giving it bulging appearance. The nucleus of such cell was located at the base of the acinar cells. The capsule of pancreas is normally a thin fibrous coating over its outer surface. Though, not a frequent finding, capsule showed considerable thickening due to deposition of connective tissue. The thickened capsule often showed infiltration of inflammatory cells. Sub capsular necrosis and individualization of acinar cell had also been observed.

Earlier in a study on runting stunting syndrome, 16.65% birds exhibited pancreatic pathology⁶. Highest percentage of birds showed bleached or congested pancreas. Anemia, interstitial fibrosis, degenerative and infiltrative changes could be the major underlying factor for bleached pancreas. Congested pancreas mostly results due to interference in venous return and increased intra-abdominal pressure in disease conditions such as chick edema disease, hepatitis, nephrosis, colisepticemia, yolk sac infection, oophoritis etc, as evidenced in present study. Similar to our findings, congestive changes in pancreatitis has also been requested in guinea fowls⁷. In addition, pancreatic deformity was observed consistently in different bacterial and viral diseases of poultry. It was mostly associated with interstitial fibrosis as a result of persistent irritation and degenerative changes under different disease conditions. Pancreatic deformity has the potential to bring obstructive changes in pancreatic ducts and blood supply; these may interfere with secretary function of exocrine pancreas thereby contributing to altered physiology of digestive system and poor health. Terminal bending of pancreas and duodenum has been reported in Parvovirus infection⁸. In pancreatic atrophy, emaciation and cachexia becomes major manifestation due to destruction of both exocrine and endocrine pancreatic parenchyma as observed in present study. Nutritional deficiency of protein, amino acids, vitamin A, trace elements such as zinc, copper and selenium under chronic disease condition also contributes to pancreatic atrophy^9.10,11.

Histopathological study of diseased pancreas brought forward two important microscopic alteration of relatively high frequency viz. multifocal necrotic lesion with infiltration of inflammatory cells, and vacuolar degeneration of acinar cells with residual bodies or apoptotic changes. Occurrence of these changes was significantly higher in viral diseases such as IB, fowl pox, lymphoid leucosis, RD, IBD, etc. Higher involvement of pancreas during viral infections such as Paramyxo type I and Avian Influenza virus in poultry has previously been reported^12,13,14.

Interstitial fibrosis and individualization of acinar cells were other important histopathological alteration in diseased pancreas. Fibrosis is always suggestive of chronic persistent infection associated with degenerative or necrotic changes. Individualization or loss of cell polarity signifies damage to the basement membrane of acini and adjascent interstitium^9,15. It is preceded by progressive depletion of zymogen granules, cell shrinkage, cytoplasmic basophilia. The cells finally loose polarity gets distorted and loose glandular arrangement. Loss of polarity of acinar cells has been described in mammals due to nutritional deficiencies and excesses. Nutritional deficiencies arising in infectious and non-infectious disease condition might have contributed to loss of polarity in the present study.

It can be concluded that the incidence of primary pancreatic pathology in poultry is rare. Its involvement as a secondary complication is quite high and may constitute an important contributory factor in variable growth rate shown by birds in cases of disease outbreak and subsequently the economic loss faced by the poultry industry. It would be beneficial to add preparations of pancreatic enzyme in the poultry ration of diseased flock, which so far is not included as a feed supplement in poultry industry as well as to add vitamin A and vitamin E to support the regenerative process and enhance profitability in poultry farming.

The study was supported by grant provided by Birsa Agricultural University, Kanke. The authors are thankful to Director Research, BAU, Kanke for providing necessary support and to the Dean, Ranchi Veterinary College, BAU, Kanke for providing necessary facilities.

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