Patologia e patogênese da infecção experimental por Salmonella Gallinarum em pintinhos de corte

Salmonella spp. outbreaks in poultry farming have been frequent in recent years, resulting in significant economic losses and public health issues. Among the serovars that infect birds, Salmonella Gallinarum biovar Gallinarum is one that has been isolated most frequently in outbreaks in young birds. In an effort to study the pathogenesis of fowl typhoid in chicks, the present study aims to experimentally reproduce enteric and systemic lesions caused by Salmonella Gallinarum biovar Gallinarum isolated from a natural outbreak of the disease. In the experiment, 160 two-day-old Ross broiler chicks were used. The birds were divided into four groups and received oral and intranasal inoculation in different doses. From the 3rd to the 12th day post-inoculation, euthanasia and necropsy were performed on the birds to collect samples for bacteriological, histopathological, and immunohistochemical examinations. Classic gross and histological lesions such as fibrinonecrotic and/or histiocytic hepatitis, splenitis, and myocarditis were found in birds of all groups. However, the occurrence of unusual lesions was also noted, such as severe cases of transmural and non-transmural histiocytic enteritis, histiocytic laryngitis and tracheitis, histiocytic interstitial pneumonia, glomerulonephritis, glomerular thrombosis, fibrinous and/or histiocytic bone myelitis, necrotic and/or histiocytic bursitis, and necrotic and histiocytic encephalitis. These lesions were attributed to Salmonella Gallinarum through the in situ labeling of the agent by immunohistochemistry in all affected tissues, as well as by the recovery of the agent in tissues such as liver and spleen in bacteriology. Additionally, it was found that when inoculated via the intranasal route, the bacteria caused a more pathogenic presentation of the disease compared to the oral route, affecting a larger number of organs and segments of the intestine. Therefore, the importance of the respiratory route in the reproduction of the disease in experimental cases and spontaneous outbreaks of the disease in chicks is highlighted.