Faecal shedding and intestinal colonization of Salmonella enterica in in-bred chickens: the effect of host-genetic background

Abstract

Considerable and reproducible differences were observed in the amount and duration of faecal excretion when in-bred lines of chickens were infected orally with S. enterica serovar Typhimurium at 6 weeks of age after being given a gut flora preparation when newly hatched. Similar but less pronounced results were observed with S. Enteritidis or S. Infantis. Differences in the viable numbers of the inoculated bacteria in caecal contents were detectable within 24 h of inoculation. No major differences were seen in Salmonella-specific serum IgA or IgG titres. Small differences were seen in the numbers of circulating heterophilic cells. Caecal contents taken from the more resistant lines immediately prior to challenge appeared to be no more inhibitory for Salmonella in vivo than contents taken from susceptible lines. The more resistant lines showed a slightly higher rate of intestinal flow, as indicated by the rate of production of faecal droppings, although there was no difference in the rate of emptying of the caeca. In an F1 generation resistance was dominant and not sex-linked. There was no MHC linkage or any association with SAL1, the gene implicated in resistance to systemic salmonellosis in chickens, or NRAMP1.

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

“…When considering resistance to oral inoculation at six weeks of age, large differences were observed [1]. The pattern of faecal shedding of the F1 birds closely resembled those of line 6 1 with rapid elimination of the challenge strain and low rates of excretion.…”

“…This result will have to be considered for any practical application. Only two of the QTL were identified in both crosses: while both age at inoculation and Salmonella serotypes differed between the two crosses, the former seemed to be more responsible for between line differences, since similar relative resistance of lines to caecal excretion were observed after inoculation with Salmonella typhimurium, Salmonella enteritidis or Salmonella infantis [1]. Moreover measures in the backcross were taken earlier (because of quicker clearance of Salmonella) and could partly involve different genes.…”

“…Therefore differences in resistance to the Salmonella enteritidis carrier-state after inoculation at one week of age between four inbred lines were first observed. In parallel, additional studies on resistance to Salmonella typhimurium after inoculation at six weeks led to the evidence of large differences between the same lines but in a different order [1]. This led us to the hypothesis that genes controlling both traits could differ.…”

“…In the (N × 6 1 )F1 × N backcross experiment, a total of 80 progeny were reared and orally inoculated at six weeks of age with Salmonella typhimurium as formerly described [1]. Cloacal swabs were studied from wk 1 to 4 but only two phenotypic measurements, i.e.…”

An assessment of opportunities to dissect host genetic variation in resistance to infectious diseases in livestock

“…Line differences in resistance to infection are well documented (Bumstead and Barrow, 1993;Barrow et al, 2004) and QTLs have been identified for resistance or antibody response (Mariani et al, 2001;Yunis et al, 2002;Tilquin et al, 2005). Associations have also been reported with a variety of candidate genes (Kramer et al, 2003;Malek et al, 2004), which include MHC polymorphisms and NRAMP Lamont et al, 2002;Liu et al, 2003).…”