ABSTRACT
Immunohistochemical study of the visceral organs of chickens experimentally infected with Salmonella Zega by three routes was carried out to compare the quantitative distribution and interaction of the organism with host cells. 100 birds comprising of 2 week-old chickens were divided into 4 groups of 25 each. Group A was inoculated orally, group B intraperitoneally, group C were administered per cloaca and D were not inoculated and served as control. All the infected birds were inoculated with 0.2 ml of 1 × 108 cfu of the bacteria. Two birds from each group were sacrificed every 24 h post infection. Samples of visceral organs were collected for immunohistochemistry. The distribution of Salmonella Zega in every organ was taken as Mean ± SD of the number of foci of immunoreactions and Compared using a 2-way ANOVA. The interaction of Salmonella Zega with host cells was determined by taking the percentage of the days post infection in which immunoreactions were detected in host cells in each route of infection. The distribution of the organism was highest in the lung of intraperitoneally infected chickens (83.95 ± 27.89) and lowest in the heart (5.21 ± 3.65) of chickens that were infected per cloaca. The highest percentage of interaction of Salmonella Zega was recorded in the epithelial (100%) and blood (100%) cells in all the routes of infection. There were variations in the distribution of Salmonella Zega in visceral organs of chickens but the level of interactions with host cells were similar even when infected through different routes.
ABSTRACT
Salmonella Zega isolated from natural outbreaks that were characterized by high mortality in poultry farms in three Southwestern States of Nigeria was used to inoculate two week-old chicks through different routes in order to determine and compare the clinical signs, pathological and immunohistochemical changes in each route of infection. The birds were divided into 4 groups of 25 each as groups A (orally inoculated), B (intraperitoneally inoculated), C (inoculated per cloaca) and D (uninoculated control). All the birds were inoculated with 0.2 ml of 1 × 108 cfu of the bacteria. Clinical signs were observed and recorded according to the route of infection, and with the days post-infection from day 0 till day 10 post-infection. Two birds from each group were sacrificed every 24 h and examined for gross lesions, which were described and scored according to the route of infection and days post-infection. Samples of visceral organs were collected for bacteriology, histopathology and immunohistochemistry. Clinical signs in chicks infected orally and intraperitoneally were weakness, anoraexia lethargy, somnolescence, yellowish diarrhoea observed from 4 days till day 10 post infections. Mild sign of weakness was observed in chickes infected per cloaca, from day 3 to 7. The gross lesions were congestion, oedema and enlargement and necrosis in visceral organs from day 4 to 10 post infection in orally and intraperitoneally infected chicks, but mild vascular changes were observed in chicks infected per cloaca, except in the caecum were lesions of necrosis and infiltration of inflammatory cells were moderate to severe. Microscopic lesions were necrosis of host cells and infiltration by lymphocytes, heterophils and macrophages in multiple organs observed from day 4 to 10 post infection in orally and intraperitoneally infected chicks. Immunoreactions were observed in all the visceral organs examined. Clinical signs, pathological and immunohistochemical findings were mild in chicks infected per cloaca, except caecal lesions. Salmonella Zega isolated from an outbreak in poultry farms in Abeokuta, Nigeria was highly pathogenic in chicken and produced similar findings in oral and intraperitoneal infections; while per cloacal infection showed a localized infection of the caecum.
