In vivo assessment of the virulence of five Salmonella enterica serotypes isolated from helmeted guinea fowl (Numida meleagris) in Benin

Abstract

The pathogenicity of five Salmonella enterica serotypes (Farakan, Kingston, Legon, Oakland, Teshie) isolated from guinea fowl in Benin was experimentally assessed by oral challenge of 25 groups of 18 two week-old keets using 0.5 ml of 104 to 108 CFU/ml of overnight broth culture. One additional unchallenged group formed a control group. Keets were observed twice daily for clinical signs until day 15 post-inoculation. Clinical signs were observed in all groups, except in keets inoculated with serotype Teshie at 104 CFU/ml. Clinical scores were higher (p<0.05) at the highest inoculum concentrations within each serotype, but also differed between serotypes. Seven deaths were recorded only in serotypes Legon and Oakland. Salmonella was isolated from faeces with all serotypes at D7 and/or D15 PI at inoculum concentrations of 106, 107 and/or 108 CFU/ml. Salmonella was also recovered at D15 PI from the caecum of two keets of each group at 107 and 108 CFU/ml (except serotype Teshie), but not from the heart blood; there was only one from the liver. These five Salmonella serotypes are not only able to colonize keet intestines but also cause clinical signs similar, though less dramatic to those observed during field surveys.