Clinicopathology of sodium bicarbonate induced gout in broiler chicken model Ali Rayeesa1, Kamil S.A.1,*, Amin U.1, Mir M.S.1, Shah A.1, Kashani B.1, Dar T.A.1, Shah S.A.1, Qureshi Sabia1 1Division of Veterinary Pathology, Faculty of Veterinary Sciences & Animal Husbandry, Sher-e-Kashmir University of Agricultural Science & Technology (SKUAST-K), Srinagar-190006, Jammu and Kashmir, India *Corresponding author: e-mail: kamilshoaib@gmail.com
Abstract Clinicopathological changes due to sodium bicarbonate induced gout in broiler chickens were investigated. Seven-day old broiler chickens were randomly divided into 3 groups (n=12). Group I served as vehicle-treated control, Group II and III were given sodium bicarbonate @ 2.5% and 5% respectively, in drinking water. Clinical signs developed progressively from 4th day of the exposure. 25% and 58.33% mortality was recorded in Group II and III, respectively. Deposits of chalky white urates were prominently seen in kidneys, liver, heart and proventriculus. Histopathological lesions included severe degeneration and necrosis of renal tubules and heterophil infiltrations; large focal areas of coagulative necrosis, congestion of central vein, fatty change and periportal and paraportal lymphoid infiltrations in liver; degeneration of cardiac muscles; and congestion and serous exudate in parabronchi of lungs. Thymus revealed severe congestion, degeneration and necrosis of lymphoid tissue with serofibrinous exudate. Masson's Trichrome stain revealed fibrosis in kidneys, liver, heart and lung tissues, whereas De Galantha's stain showed urate deposits as tophi or amorphous material. Top Keywords Chicken, DeGalantha's stain, Gout, Masson's trichrome, Sodium bicarbonate, Thymus, Urates. Top |
INTRODUCTION Gout is one of the important diseases in poultry where kidney is the main organ involved1. It is characterized by reduction in kidney‘s function by several factors which results in hyperuricemia (uric acid >10 ml/dl) leading to deposition of calcium-sodium urate crystals, particularly in kidneys and other visceral organs2,3. Two forms of gout, articular and visceral gout occurs in poultry depending upon the sites of urate deposition. Visceral gout is characterized by the deposition of urates in kidneys, on heart, serosal surfaces, liver, mesentery, air sacs and peritoneum or urates may also found in spleen and other organs4,5-6 while the articular gout is characterized by deposition of urate around the joints. Articular gout is chronic form with low incidence and has little economic aspect3,4,5,6-7. It is considered as sporadic individual problem while the visceral gout may occur in the form of outbreaks, causing heavy mortality in commercial poultry. However, the concurrent occurrence has also been observed8. |
There are many causes of goat as kidney damage occurs due to multi-etiological factors such as nutritional and metabolic factors, infectious causes and toxicity. Sodium bicarbonate which is commonly used in broilers to combat heat stress has also been used in layer bird diets to improve egg shell quality9. However, the excess use of sodium bicarbonate in poultry leads to visceralgout10,11. Therefore, the present study was designed to investigate the clinicopathology of sodium bicarbonate induced gout in chickens. |
Top MATERIALSAND METHODS Animals Day old broiler chicks of Ross breed were procured from commercial hatchery. The broiler chicks were maintained under brooding temperature for 7 days in a single pen under standard management practices. The experiment was carried out in accordance with the guidelines prescribed by the committee for the Purpose of Control and Supervision of Experiments on Animals (CPCSEA) and the study was approved by the institutional animal ethics committee (IAEC) of SKUAST- Kashmir. Experimental groups After brooding for 7 days, the birds were randomly divided into 3 groups with 12 birds in each group. Group I served as vehicle-treated control and was given drinking water. Group II was given sodium bicarbonate @ 2.5% (w/v) and Group III was given sodium bicarbonate @ 5%(w/v) in drinking water. The birds were sacrificed at the end of 1st, 2nd and 3rd week post exposure and the following parameters were determined. Clinical observations Experimental birds were closely observed twice daily throughout experimental period for clinical signs. The mortality in different groups was recorded and the percent mortality was calculated. Pathology Sacrificed as well as those birds died during experimentation were necropsied and thoroughly examined for macroscopic lesions. The lesions were recorded and compared at the end of experiment. Representative tissue samples from different organs like kidneys, liver, heart, lungs, thymus, proventriculus, intestine, spleen and bursa of Fabricius were collected and fixed in absolute alcohol. Later, paraffin embedded tissue sections of 5 μm thicknesses were cut and then stained with Harris Hematoxylin and Eosin (H&E) stain12. Special staining technique DeGalantha‘s was used for demonstration of urates13 and Masson‘s Trichome for fibrous connective tissue12. Top RESULTS Clinical signs Birds of all the three experimental groups were observed daily for clinical signs post exposure to sodium bicarbonate. The control group birds (Group I) did not show any apparent clinical sign. However, moderate to severe clinical signs were observed in birds belonging to Group II and Group III which started from day 4th of the experimental period. Initially in both groups, the birds revealed dullness, ruffled feathers, closed eyes and reduction in feed and water intake. At latter stage, the birds belonging to treatment groups revealed laboured breathing, dropped wings and were seen sitting on hocks with their eyes closed. The intensity of clinical expressions was more severe in birds belonging to Group III compared to Group II. Mortality pattern An overall mortality of 25% and 58.33% was observed in birds belonging to groups II and III respectively, throughout the course of experiment. However, no mortality occurred in birds of control group (Table 1). Pathological studies All the organs were properly observed for lesions at the time of necropsy and the lesions were recorded.The severity of lesions was more in birds that died during the experiment compared to those that were sacrificed. Gross pathology Kidneys Kidneys were severely swollen with congestion and ecchymotic hemorrhages at early stage followed by discoloration and urate deposition which was progressively severe. Changes were more severe, extensive and appeared early in Group-III (Fig. 1-A, B). Liver The liver in Group II birds appeared pale at 1stweek post exposure and revealed congestion amidst deposition of chalky white urates at 2nd week post exposure. While at 3rd week post exposure, the liver from birds were enlarged, swollen, congested and covered with urates. The lesions in liver of Group III birds were friable, enlarged and covered with excessive amounts of whitish deposits of urates indicating much more intense tissue damage (Fig. 1- C). Heart During 1st week post exposure, birds of Group II revealed congestion of heart. However, at 2nd and 3rdweek post exposure, pericardium showed deposition of urates. The deposition of urates was more abundant and more severe in Group III birds. Some of birds in Group III at 3rd week post exposure revealed collapsed heart with gelatinization of epicardial fat. Lungs At 1st week post exposure no lesions were observed in Group II birds. However, congestion, haemorrhages and frothy exudate were observed at 2ndand 3rd week post exposure. These lesions were severe and observed throughout the course of experiment in Group III birds. Proventriculus In few birds of intoxicated groups mild urate deposition in form of foci of white chalky material was observed on the proventricular serosa at 3rd week post exposure. Intestines Intestines revealed congestions at different intervals of the experiment. Thymus, spleen, pancreas and bursa of Fabricius did not reveal any appreciable gross pathological lesions during the course of study. Histopathological observations Kidneys Birds of Group II revealed hydropic degeneration and necrosis of kidney tubules (Fig. 1-D). Cortical glomeruli showed shrinkage. Urinary space was increase and kidney tubules were filled with eosinophillic mass and edematous fluid. Also, there were infiltrations of lymphocytes in the interstitium. Both cortex and medulla were involved during 2nd and 3rdweek post exposure. Some of the tubules were filled with RBC‘s. Collecting tubules revealed urate crystal deposits as pink radiating masses. Also, there were multiple necrotic areas in the cortex (Fig. 2-A). Cortical epithelial hyperplasia and obliteration of tubules by fibrotic tissue was also evident. Lesions were more severe in Group III birds compared to Group II. There was hyperplasia of mesangial cells, vacoulation of tubular epithelium and infiltration of mononuclear cells in between the tubules. In severe cases especially from 2nd and 3rd week post exposure, besides above changes the lining epithelium of tubules was completely denuded and urate deposits in the form of amorphous material and pink radiating crystals admixed with necrotic debris were found in the Bowman‘s capsule, tubules and interstitial tissue (Fig. 2-B). De Galantha‘s staining showed urate deposits as black crystals in degenerated and necrotic tubules of cortex and medulla (Fig. 2-C). Masson‘s trichrome staining revealed fibrosis as bluish fibres (Fig. 2- D). Liver Birds of Group II during initial stages showed disintegration of hepatic cords, degeneration and clumping of hepatocytes. During later stages of experiment, the hepatocytes revealed increased granularity amidst loss of nuclei in marked number of hepatocytes. Also, multifocal areas of necrosis with urates in form of radiating structures were seen. In few cases, discontinuity in the walls of blood vessels and leaking of erythrocytes filled the sinusoidal spaces. Some of the necrotic areas were surrounded by large amounts of heterophils and lymphocytes. Birds of group III during initial stages revealed similar but more severe changes which include periportal fibrosis, infiltration with lymphocytes and heterophils and necrotic areas in hepatic lobules. In some cases, there were large focal areas of coagulative necrosis without deposition of amorphous material (Fig. 3-A). With De Galantha‘s stain urate appeared as black needle shaped crystals in necrotic areas either singly or in clumps (Fig. 3- B). Heart The changes in the heart were observed during 2nd and 3rd week of the experiment. The heart muscles revealed hemorrhage and degeneration during initial stages. While during 2nd and 3rd week there was necrosis of pericardium together with deposition of urates in form of amorphous material in necrotic areas. Also, there was oedema and leucocytic infiltration in between the muscle fibers. Epicardial fibrosis appeared as bluish spindle shaped fibers on Masson‘s trichrome stain. De Galantha staining revealed presence of urates in form of black crystals in both pericardium and endocardium. Lungs Group II birds revealed severe congestion of parabronchi, atria and air capillaries. Also, there was oedema of parabronchus. Moreover, in some birds epithelium was thickened and epithelium of atria and capillaries were hyperplastic. In addition to above changes, Group III revealed thickened interlobular septa and emphysema. Some air capillaries were collapsed. Furthermore, pulmonary tissue was completely replaced by fibrous connective tissue as demonstrated by Masson‘s trichrome stain. Suppurative pneumonia characterized by the presence of necrotic tissue with infiltration of heterophil and mononuclear cells in the parabronchi and secondary bronchi was also seen. Thymus Thymus revealed severe congestion, degeneration and necrosis of lymphoid tissue with serofibrinous exudate. Spleen Mild lesions were observed in Group II and III birds during 2nd and 3rd week of experiment. Spleen showed degeneration of lymphoid tissues, reticular endothelial cell hyperplasia and thickening of endothelial lining of sheathed artery. Also, depletion of lymphoid tissue in the Malpighian corpuscles was observed. Proventriculus Proventriculus revealed degeneration and denudation of glandular epithelium. In some cases, lumen of glands was filled with necrotic debris and bluish amorphous material. Inter-glandular connective tissue was thickened. Secondary and tertiary ducts were filled with oedematous fluid. Also, goblet cells exhibited hyperplasia and plicae were necrosed. Intestines Villi were degenerated and lumen was filled with cellular debris and oedematous fluid. Top DISCUSSION Sodium bicarbonate is beneficial for poultry. It is used as laxative, increases the egg shell thickness14, improves body weight gain and decreases losses due to heat stress9. Moreover, sodium bicarbonate has been used to correct acid base imbalance. However, these above mentioned beneficial effects can be attained only when the recommended doses are administered. Excessive dose results in kidney damage and gout15,16. In the present study, the observed clinical signs in sodium bicarbonate intoxicated birds might be attributed to acid-base imbalance due to nephropathy17,18,19,20-21. |
The dose dependent pattern of mortality may be attributed to kidney or heart failure as evidenced by severe morphological lesions in these organs and corroborated with earlier workers in bicarbonate or diclofenac induced gout12,20,21. Lesions in kidneys, liver, lungs, heart and other organs might be attributed to the damage as a result of crystallization of urates as was evident from gross and histopathology. More or less similar lesions has also been reported previously17,18,22,23,24,25,26,27,28,29,30,31,32,33-34. Lesions in proventriculus were similar to those reported by Gajera25. In spleen radiating urates as reported earlier were not evident28. Lesions in thymus which included severe congestion of thymic lobes and serofibrinous exudate are unique findings of this study and have not been reported earlier. |
It was concluded that sodium bicarbonate at both 2.5% and 5% (w/v) concentrations can cause gout in birds and could produce severe pathomorphological changes in visceral organs including kidneys, liver, heart, lungs, thymus, spleen and intestines. |
Top ACKNOWLEDGEMENTS The present study is a part of post-graduate thesis research. All the facilities and funds provided by Head of the Division and the Dean Faculty are highly acknowledged. |
Top Figures | Fig. 1.: (A) Hemorrhagic, swollen and urate filled kidneys and ureters of Group II birds; (B) Kidneys of Group III birds puffed up with whitish urate deposits; (C) Urate deposits on liver and heart of Group III birds; (D) Degenerated and necrotic tubules filled with urates and leucocytic infiltrations. HE ×100
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| | Fig. 2.: (A) Large necrotic areas surrounded by dilated and degenerated tubule. Note increase in urinary space (arrow). HE ×400; (B) Urate deposits in the form of tophi. HE ×400; (C) Urate deposits as black needles. De-Galantha x400; (D) Fibrosis of kidney evident as blue collagen fibers. Masson‘s Trichrome x400.
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| | Fig. 3.: (A) Focal area of coagulative necrosis in liver (arrow). HE ×400; (B) Black radiating urates within necrotic lesion in liver. De Galantha x400.
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Table | Table 1.: Mortality rate observed in different experimental groups.
| | Group | Total birds | Mortality during experimental period | Total mortality | Percent mortality | | 1st week PE | 2nd week PE | 3rd week PE | | I | 12 | 0 | 0 | 0 | 0 | 0 % | | II | 12 | 0 | 1 | 2 | 3 | 25% | | III | 12 | 3 | 2 | 2 | 7 | 58.33% |
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| PE = Post exposure | |
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