Estimated heritability of the resistance to cecal carrier state of Salmonella enteritidis in chickens

Abstract

Previously, we have shown differences in susceptibility to the cecal carrier state in chicks orally infected with Salmonella enteritidis (SE) at 1 wk of age for four outbred lines: L2, B13, PA12, and Y11. The egg-type line L2 was one of the most susceptible lines and presented a large variability in cecal SE colonization. The heritability (h2) of the resistance to SE colonization in ceca was estimated in L2 chickens to determine whether genetic factors might be involved in its control. In three independent trials, a total of 819 L2 chicks produced from 88 sires and 232 dams were challenged orally with SE at 1 wk of age. Each week after inoculation, the frequency of cecal colonization was estimated. When this value had fallen to 50%, all the remaining animals were killed. The extent of cecal colonization by SE was estimated directly by counting the viable organisms in organs and determining the numbers of positive ceca. Enrichment culture was used in Trials 2 and 3. The effects of trial, of room within trial, and of cage within room on the frequency of SE contaminated ceca were often significant. No significant effect of sex was observed. Estimation of h2 using the frequency of SE positive ceca was low, 0.06 +/- 0.07, when results of direct culture were considered. In contrast, when considering the frequency obtained after enrichment, the h2 was estimated at 0.20 +/- 0.12. This result suggests a genetic basis for the expression of the resistance to colonization. An experiment of selection for resistance to SE carrier state in the chicken ceca should definitively confirm the genetic origin of the resistance.

Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

“…Vaccination and competitive exclusion are important methods to aid reducing S. Enteritidis poultry infection [37,96,153]. The prevalence of Salmonella in animals may also be reduced by the genetic selection of animals resistant to disease but also to the asymptomatic carrier state [13,15,77]. However, our increasing understanding of the molecular fluidity of the genome suggests that any attempt at extensive biological intervention will result in a further evolution, as the bacterium attempts to overcome the obstacle placed in its ecological path.…”

Genetic resistance to mortality of day-old chicks and carrier-state of hens after inoculation withSalmonella enteritidis

“…In their work, the L2 line was classi® ed as susceptible and some within-line variation could be observed. Berthelot et al (1998 ) estimated that in the L2 line the heritability of the presence of Salm onella in caeca after oral inoculation of 1-week-old chicks was 0.20 6 0.12. Nothing is known of the mechanisms of resistance to the contamination of caeca.…”

A genome scan for quantitative trait loci affecting the Salmonella carrier-state in the chicken

“…In order to address this question, experimental models of infection were defined in chicks [15] and adult hens [31]. By using these models, the heritability of resistance was estimated at 0.20 in young birds [4] and more than 0.35 in laying hens [2]. These results show that the Salmonella carrier-state is partly genetically controlled.…”