Experimental infection of laying hens with Salmonella enterica serovar Gallinarum

Infecções experimentais por Salmonella enterica serovar Gallinarum foram realizadas em aves de postura comercial, incluindo uma linhagem branca resistente e uma linhagem vermelha susceptível ao desenvolvimento da enfermidade clínica. As aves de linhagem susceptível apresentaram doença clínica dependente da dose administrada. Excreção fecal foi observada em aves da linhagem susceptível próximo ao momento da morte e, eventualmente, em aves da linhagem resistente e aves convalescentes. A remoção das aves mortas do meio ambiente reduziu a taxa de mortalidade/morbidade, procedimento este que pode ser utilizado como medida de controle.

Prevention of Salmonella infection by contact using intestinal flora of adult birds and/or a mixture of organic acids

This study was carried out to assess the ability of competitive exclusion and a mixture of organic acids to prevent "Salmonella" infection by contact between newly hatched chicks. A bird infected with "Salmonella" was placed in a box containing non-infected birds, previously treated with a broth culture of faeces of adult birds (CE) and/or a mixture of organic acids. The number of "Salmonella" organisms in the caeca of the contact birds was estimated at 4 and 8 days post-challenge. The birds were infected with "Salmonella" Typhimurium, "Salmonella" Enteritidis (both repeated 5 times), "Salmonella" Agona and "Salmonella" Infantis (3 repetitions). The same approach was used to test the mixture of organic acids alone. In this case the birds recieved feed containing 0.8(per cent) of a mixture of formic acid (70(per cent)) and propionic acid (30(per cent)). Also, a third trial was carried out with birds inoculated with the broth culture of faeces and fed with feed containing the mixture of organic acids. Appropriate controls were included. Whereas the birds from the control groups and the groups treated with the mixture of organic acids were heavily infected with "Salmonella", those pre-treated with CE or CE plus the mixture of organic acids had no viable cells per gram of caecal contents.

Experimental Salmonella Gallinarum infection in light laying hen lines

Although the epidemiology of fowl typhoid in chickens supposedly involves a vertical transmission stage, a previous work run by the authors has suggested that this did not happen in a commercial line of laying hens highly susceptible to systemic disease with Salmonella Gallinarum. A new experiment was carried out in two other lines of commercial layers, considerably more resistant than those used in the previous study. Clinical fowl typhoid was not observed, but Salmonella Gallinarum was isolated from spleen and liver four weeks after infection and, sporadically, from the ovary.