Pathology of experimental pasteurellosis in ducks
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Date
2009
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Centre of Excellence in Pathology, College of Veterinary and Animal Sciences, Mannuthy
Abstract
The present study was undertaken to evaluate the pathological aspects of pasteurellosis in ducks following experimental inoculation by different routes – subcutaneous and intranasal. The haematobiochemical changes associated with the infection were also studied.
Body weight changes at weekly intervals, mortality pattern, haematological and biochemical parameters such as total erythrocyte count, total leucocyte count, haemoglobin concentration, differential leucocyte count, total protein, albumin and globulin values estimated at weekly intervals were the parameters used, to study the changes caused by the infection. Gross pathological changes and histopathological changes of heart, liver, lung, kidney, brain, intestine, spleen, caecal tonsils and bursa were also studied.
Statistically significant alteration was not observed in body weight. Mean Hb, TEC, PCV, albumin, heterophil and eosinophil percentage values were markedly increased after infection. Correspondingly, the lymphocyte and monocyte counts and the total protein values showed a significant decrease.
Acute onset of the disease with sudden mortality was noticed in subcutaneously inoculated birds. Peracute death without any symptoms and lesions was shown by two birds in this group. The peracute pattern of mortality seen in this group was not observed in intranasally inoculated group. But the severity of clinical signs and lesions were more in intranasally inoculated birds. After the first two peracute deaths, symptoms of acute toxaemia such as pyrexia, dullness, depression, inappetence, reluctancy to move, paralysis of limbs and neck and incordination were expressed by the birds before death.
The birds died from second day after inoculation onwards revealed an acute haemorrhagic septicaemic picture on all visceral organs. Haemorrhages on epicardium and scattered pin point necrotic foci in the liver, the prominent lesions of fowl cholera, were clearly evident. These lesions were more pronounced in the birds inoculated intranasally with P. multocida, which died on 23rd, 24th and 25th day post- inoculation. The lung and brain lesions were more severe in these birds.
Reisolation of P. multocida was carried out from the liver, heart and spleen of all the dead birds except control and survived birds.
The present study proved that the route of entry of organism played a significant role in the progression of infection, onset of mortality, number of deaths and symptoms and lesions in fowl cholera outbreaks. The immune suppression due to lymphoid organ damage in fowl cholera make the birds more susceptible to other infections.
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