Peter De Herdt

Pathogenesis of infections with Salmonella enterica subsp. enterica serovar Muenchen in the turtle Trachemys scripta scripta.

The pathogenesis of Salmonella enterica subsp. enterica serovar Muenchen infections in the aquatic turtle Trachemys scripta scripta was studied. After oral infection with 5x10(5)cfu of serovar Muenchen of 10-14-month-old turtles, kept at 26 degrees C, the intestine and especially the ileum, caecum and colon was colonized. Invasion of the intestinal wall, causing histopathological lesions, and colonization of internal organs were not observed. Serovar Muenchen was only isolated from turtles for 8 days after exposure. Keeping the turtles at 37 degrees C caused colonization of liver and spleen in two of six orally infected turtles and augmented the numbers of bacteria in the intestinal tract. In contrast to oral infections, intraperitoneal infections of turtles with serovar Muenchen enabled the bacterium to persist inside the host for at least 5 weeks. Clearance of serovar Muenchen from the liver and blood was more pronounced at 26 degrees C than at 37 degrees C. ELISA antibodies were demonstrated in intraperitoneally but not in orally infected turtles kept at 26 degrees C. In conclusion, the lack of persistence and invasiveness of serovar Muenchen in T. s. scripta after oral exposure might be due to the turtles relatively low body temperature and/or the absence of well-organized gut-associated lymphoid tissue.

Adhesion of Streptococcus gallolyticus strains to extracellular matrix proteins.

Fourteen pigeon Streptococcus gallolyticus strains of differing virulence, were tested for their ability to adhere to immobilised fibronectin, collagen types I, III and IV. Eight, 2 and 13 strains were able to bind fibronectin, collagen types III and IV, respectively. None of the strains adhered to collagen type I. Heat treatment, proteolytic digestion or periodate treatment reduced the binding of S. gallolyticus to fibronectin and collagen type IV, suggesting that surface receptors contain proteins and carbohydrates. Although binding to these extracellular matrix proteins can play a role in the pathogenesis of streptococcosis in pigeons, binding properties could not be related to virulence, indicating that other factors determine differences in virulence among pigeon S. gallolyticus strains. Adhesion to collagen type IV may account in part for the distribution pattern of the lesions observed in naturally and experimentally infected pigeons.

The effect of vaccination on the course of an experimental Salmonella typhimurium infection in racing pigeons.

Two killed adjuvanted vaccines were evaluated for their efficacy against salmonellosis in pigeons. Both vaccines contained whole-cell formaldehyde-inactivated Salmonella typhimurium var. Copenhagen bacteria. Two groups of 10 pigeons were inoculated twice with a 3-week interval with one of the vaccines. Ten weeks after the second vaccination, all vaccinated pigeons as well as 10 non-vaccinated birds were challenged by crop inoculation of 109 colony-forming units of a Salmonella serotype Typhimurium var. Copenhagen strain. Ten pigeons that were not vaccinated or challenged served as negative controls. As determined by clinical examination, plasma chemistry and necropsy, neither vaccine induced protection against challenge. The only significant effects observed were a reduction in the level of faecal shedding and a less severe polydipsia in the pigeons treated with one of the two vaccines. Results of this study indicate that vaccination against salmonellosis in pigeons with killed vaccines may not be very useful. However, the ability of certain vaccines to reduce shedding may contribute to the control of salmonellosis in infected pigeon lofts.

Improved Performance of Broilers and Broiler Breeders Associated with an Amended Vaccination Program Against Reovirosis

SUMMARY A vertically integrated monitoring program was set up for breeders hatched in 2013 and their offspring to detect differences in performance related to the reovirus vaccination schedule. Within the same organization in Belgium, 17 breeder flocks were vaccinated with one dose of live and one dose of inactivated reovirus vaccine, while 14 flocks received two doses of inactivated vaccine without live priming. The hatchability of the eggs produced by these birds was examined. Further, the daily growth, feed conversion, mortality, slaughterhouse condemnation, production index, and antibiotic use were monitored in 110 broiler flocks derived from the breeders. All gathered data were examined statistically. In eggs obtained from breeders vaccinated twice with inactivated reovirus vaccine, a significant 2.88% higher hatchability rate was observed. The progeny broiler flocks of these breeders showed a significant 18.2% lower mortality during the fattening period. Although not statistically significant, the slaughterhouse condemnation rate was 10.1% lower as well. The results may indicate that—under the epidemiologic conditions of this study—double administration of inactivated reovirus vaccine in broiler breeders can at least contribute to higher hatchability of breeder eggs and lower broiler mortality.