Innocuità ed efficacia protettiva del ceppo attenuato Salmonella gallinarum SGP695AV nel pollo

Safety and protective efficacy of the attenuated strain Salmonella gallinarum SGP695AV in chickens. Fowl typhoid, caused by Salmonella enterica subsp. enterica ser. Gallinarum, causes heavy economic loss to the industrial poultry farms due to its strong impact in terms of mortality and morbidity. Furthermore, its management is quite difficult, as the infectious agent may remain in the poultry farms even during sanitary breaks. Therefore, many Countries have implemented strict preventive measures, leading the disease to be eradicated in many Western Countries. Notwithstanding, fowl typhoid is still widely diffused in the Mediterranean Countries, and in Africa, Asia and South America as well. Among the preventive measures needed to control the disease, the vaccination plays a pivotal role. To date, the only available vaccine consists of a rough strain of S. Gallinarum. The aim of this work was to assess the protective efficacy and safety of a live attenuated strain, termed SGP695AV. At T0 and 15 days after (T15), 2x107, 2x109 and 2x1011 UFC of SGP695AV were administered per os to three group of 12 30-day old laying hens, termed A, B and C, respectively. On the other hand, a verified pathogenic S. Gallinarum strain, SG354 were administered per os to another group, termed P, at T0. An equal volume of physiological solution was administered to the group N at T0 and T15. Thirty-seven days after the first administration (T37), 5 randomly chosen chickens from the groups A, B, C and P were humanly sacrificed to evaluate the presence of SGP695AV in livers, spleens and guts. Contemporary, the other animals of groups A, B, C and N were inoculated per os with 1x1013 UFC of SG354. Everyday, each animal was observed to assess its clinical score on the basis of its symptomatology. Serological test by rapid serum agglutination was performed at T0, T15, T37 and 15 days after administration of SG354 (T52). Daily, cloacal swabs were collected to evaluate the fecal excretion of SGP695AV and/or SG354. The data we gathered showed that vaccine did not cause significant adverse effects in chicken. Before T37, Clinical scores was low in A, B and C groups, even when higher doses of the vaccinal strain were administered. Contrarily, the clinical score of the group P between T15 and T37 was up to 200 times higher than those of the groups A, B and C. After infection with SG354, the clinical scores remained low in the three vaccinated groups. The excretion of SGP695AV was low and limited to the first 15 days. The fecal elimination of SG354 after T37 was equally low in the groups A, B and C, while was significantly more consistent in the group N.