An integrated approach of genetic resistance to Salmonella carrier state in fowls: from genetics to genomics and modelling.
Increasing resistance to acute Salmonellosis (that is, contamination level shortly after infection) is not sufficient to reduce the risk for consumers to be contaminated by Salmonella. Indeed, animals may remain contaminated at a low level for weeks or months. Increased resistance to the Salmonella carrier state, i.e., animals' ability to clear bacteria, is needed; it involves measuring bacterial contamination several weeks after inoculation with a low dose. To study such resistance traits, three convergent approaches were used. A quantitative trait loci (QTL) study was performed, taking advantage of inbred lines differing in resistance. Several QTLs controlling resistance at a younger age were identified and are currently being confirmed in a new cross before finer mapping, using advanced intercross lines. These inbred lines are also presently being compared using functional genomics. In parallel, a selection experiment for increased or decreased resistance at a younger and a later age was undertaken. Besides providing genetic models differing in their levels of resistance, it underlined the importance of the choice of selection criterion, whether marker assisted or not. Indeed, genes controlling resistance are strongly dependant on age; selecting for resistance at a younger age might result in increased susceptibility at an older age. Finally, the results of this experiment were used in a model of the intra-flock propagation of Salmonella. It showed that introducing a proportion of resistant animals within a flock of susceptible hens could dramatically change the evolution of contamination. Moreover, it demonstrated the magnitude of synergy between selection and vaccination, which should enhance the interest of increased resistance. The results show that selection for increased resistance to the Salmonella carrier state may be efficient, providing that the appropriate criteria of selection are used.
Beaumont
C
C
Lecerf
F
F
Protais
J
J
Calenge
F
F
Prevost
K
K
Lalmanach
A C
AC
Chapuis
H
H
Pitel
F
F
Burlot
T
T
Sellier
N
N
Fravalo
P
P
Vignal
A
A
Velge
P
P
D000818:Animals; D002353:Carrier State; D002645:Chickens / Q000235:genetics*; D023281:Genomics; D040641:Quantitative Trait Loci; D012481:Salmonella Infections, Animal / Q000235:genetics* / Q000276:immunology