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Aflatoxin B1 induced pathomorphological changes in lymphoid organs of broilers Arulmozhi A.*,2, Varghese Koshy1,2 2Department of Veterinary Pathology, Veterinary College and Research Institute, Namakkal, Tamil Nadu 1Centre of Excellence in Pathology, College of Veterinary and Animal Sciences, Mannuthy, Kerala *Corresponding author: email: arulvinod2000@yahoo.co.in
Abstract The present study reports the pathomorphological changes in lymphoid organs induced by aflatoxicosis in broiler chicken. One hundred and eighty day-old broiler chicks were obtained and divided into six groups of thirty birds each (Group I, II, III, IV, V and VI) and they were given 0, 20, 40, 60, 80 and 100 ppb of AFB1 respectively. Severe lymphoid depletion along with decreased bursa weight were recorded in Group IV, V and VI. Spleenic atrophy and lymphoid depletion was noticed in all the groups except in Group V and VI on 45th day. Thymus revealed lymphoid depletion in all the groups throughout the experimental period. Top Keywords Aflatoxin, Liver, Spleen, Thymus. Top | INTRODUCTION Immunosuppression in chicken is caused by several factors such as nutritional, managemental, diseases, stress etc. Among nutritional causes, consumption of mycotoxin suppress the immune function and decrease the resistance to infectious diseases. Among various mycotoxins, Aflatoxin B1 (AFB1) has the most potent biological effects and affect all the lymphoid organs resulting in involution or hypoplasia of the thymus, bursa and spleen and thereby interfere both humoral and cell mediated immunity. It not only attack the immune system of the dam but also the progeny as the aflatoxin carry over via the egg to the embryo which compromises the immune system and phagocytic function in progeny, leads to increased susceptiblity to various pathogens. The present study describes the morphometry, gross and microscopic alterations in immune organs of broiler chicken due to experimentally induced aflatoxicosis. |
Top MATERIALS AND METHODS One hundred and eighty (n =180), healthy, day-old broiler chicken (Hubbard) were obtained from a local hatchery and divided into six groups of thirty birds each (Group I, II, III, IV, V and VI), given scheduled experimental feed and drinking water ad libitum. Broiler chicken feed, both starter and finisher were procured from the market and the toxin level in the feed was analysed by modified Pons method1. The birds in six groups namely Group I, II, III, IV, V and VI were fed with 0, 20, 40, 60, 80 and 100 ppb of AFB1 containing feed respectively from day-old to 45 days of age. The level of aflatoxin in each category of experimental feed was adjusted by adding aflatoxin free feed to the diet containing excess toxin level and vice versa. |
Ten birds from each group were sacrificed on 15th, 30th and 45th day of the experiment. All birds were weighed before being sacrificed. A detailed necropsy was conducted and gross lesions were recorded. Bursa and spleen were recovered and weighed. Representative pieces of spleen, bursa and thymus were fixed in 10% formol saline and processed by routine paraffin embedding technique and stained with Harris haematoxylin and eosin2. The data on spleen and bursa weights were subjected to statistical analysis using analysis of variance3. |
Top RESULTS Spleen Dose dependent variation in the weight of the lymphoid organs was noticed and were summarized in Table. Although the aflatoxin fed birds showed a dose related decrease in spleen weights, but the statistically significant decrease was observed only in Group VI on 15th and 30th day and in Group II, III and IV on 45th day of experiment. But increased spleen weights were recorded in Group V and VI on 45th day. Grossly, reduction in size and spleenic atrophy was noticed in all the groups throughout the experiment except in Group V and VI on 45th day where spleenomegaly was seen. Histopathological lesions were noticed in all the lymphoid organs in varying intensity depending on the AFB1 toxin level in the feed. Mild to moderate vasculosclerosis, congestion of trabecular vessels and sinusoids were also seen throughout the experimental period in the toxin fed birds (Fig. 1). Mild to moderate lymphoid depletion from PALS, germinal centers and Peri ellipsoidal lymphoid tissue (PELT) were appreciable on 15th and on 30th day in Group IV, V and VI. PELT showed the presence of many large macrophages containing phagocytic materials, blast cells and plasma cell and patchy areas of degeneration and lysis giving a moth eaten appearance in group VI on 30th day and these lesions were well pronounced on 45th day. Bursa There was no significant difference in bursa weight between aflatoxin and control group on the 15th day, whereas, a significant increase in bursa weight was noticed in Group IV, V and VI on 30th day but significant decrease in bursa weight was noticed in Group IV, V and VI on 45th day. Enlarged and edematous bursa along with grayish white colloidal material in the lumen was observed in all toxin fed groups on 15th day and it was in higher degree on 30th day in Group IV, V and VI. Whereas, small, atrophic bursa and lumen containing necrotic material was noticed in Group IV, V and VI on 45th day of experiment. The bursa of all the toxin fed groups on 15th day revealed mild lymphoid depletion from the medulla and to a lesser extent from the cortex of the follicles. Whereas, moderate to severe lymphoid depletion in the bursal follicles was noticed in Group IV, V and VI on 30th day of experiment. Bursa follicles also showed degenerative and necrotic changes, lysis of the follicle along with intrafollicular cyst formation (Fig. 2). In addition to the above changes, intense fibrous tissue proliferation and mild reticulo endothelial hyperplasia at the cortico medullary junction were seen on 45th day of experiment. Thymus Thymus was found small and atrophied in Group IV, V and VI throughout the experiment period. It showed lymphoid depletion in dose related manner throughout the experiment. Mild lymphoid depletion was noticed in thymus cortex on 15th day in Group IV, V and VI. Moderate to severe lymphoid depletion was noticed in Group IV, V and VI on 30th and 45th days of experiment (Fig. 3). Top DISCUSSION The reduction in spleen weight in toxin fed groups might be due to lympohoid depletion in Peri arteriolar lymphiod sheath (PALS) and Peri ellipsoidal lymphoid tissue (PELT) which was evidenced on microscopic examinations. This clearly implies the immunosuppressive action of aflatoxins4. The increase in spleen weight in Group V and VI at 45th day by reticulo endothelial hyperplasia and vasculosclerosis may be due to stimulatory effect of aflatoxin on the connective tissue5. Increased bursa weight by means of interfollicular connective tissue proliferation and reticuloendothelial hyperplasia might be due to the stimulatory effect of the toxin on the reticulo endothelial tissue or due to the repair and replacement of degenerated and lysed follicles with fibrous tissue6. Atrophy and decreased bursa weight might be due to lymphoid depletion, degeneration, necrosis and lysis of lymphoid cells in focal areas and this finding was supported by the histopathological observations. Similar findings were also recorded by earlier workers7. Thymus atrophy noticed throughout the experimental period was a clear indication for regressive action of aflatoxin in cell mediated immunity. |
To conclude, the atrophy along with the lymphoid depletion in the bursa, thymus and spleen suggested that these lesions in the lymphoid system are the reliable indicator for immuno suppressive action of aflatoxicosis. Though the pathomorphological changes of lymphoid organs were seen in all the toxin fed groups, the marked and significant changes were detected only in 60, 80 and 100 ppb AFB1 groups. |
Top Figures | Fig. 1.: Spleen showed vasculosclerosis and mild lymphoid depletion in 100 ppb aflatoxin fed birds on 45th day. H&E x250.
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| | Fig. 2.: Bursa follicle showing lymphoid depletion, degeneration and lysis with cyst formation in 60 ppb aflatoxin fed birds on 15th day. H&E x250.
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| | Fig. 3.: Thymus showing mild lymphoid depletion in 60 ppb aflatoxin fed birds on 30th day. H&E x250.
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Table | Table 1.: Weight of the spleen and bursa in experimental aflatoxicosis
| | Group | Toxin level (ppb) | Spleen weight(g) | Bursa weight(g) | | 15th day | 30th day | 45th day | 15th day | 30th day | 45th day | | I | 0 | 1.427±a0.040 | 1.558± a0.105 | 2.770± a0.183 | 2.440± 0.180 | 3.958± a0.180 | 5.236±0.156 | | II | 20 | 1.396± a0.018 | 1.459± a0.053 | 2.394±0.084 | 2.440± 0.085 | 3.061± a0.169 | 8.209±0.234 | | III | 40 | 1.369± a0.032 | 1.498± a0.053 | 2.458±0.729 | 2.669± 0.165 | 3.099± a0.335 | 7.115±0.456 | | IV | 60 | 1.297± a0.025 | 1.469± a0.079 | 2.394±0.085 | 2.877± 0.158 | 4.275±0.453 | 3.477±0.244 | | V | 80 | 1.228± a0.025 | 1.376± a0.049 | 3.072±0.085 | 2.645± 0.196 | 5.257±0.479 | 3.361±0.759 | | VI | 100 | 1.183±0.123 | 1.354±0.049 | 3.234±0.263 | 2.178± 0.177 | 5.530±0.253 | 3.299±0.310 | | F value | 4.186** | 2.642* | 4.240** | - | 9.389* | - | | CD | 0.216 | 0.22 | 0.201 | - | 1.152 | - |
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| *P<0.05; **P<0.01; Means having the same superscript did not differ significantly from the control. | |
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