Juan_Castro Marquez

Furthermore, stress related suppression of the active immune system has also been related
with intestinal infection and pathogen shedding (Vilte et al., 2011). The term “super shedders”
has been used to describe animals which shed E. coli O157 at higher levels and for a longer
duration compared to other animals in the same herd. One possible factor that may influence the
presence of “super shedders” is immunosuppression potentially related to stress. Indeed,
dexamethasone-treated calves (i.e. corticosteroid immunodepressed) have been shown to
increase E. coli shedding by ~33% (p=0.04) during the days when they are immunosuppressed
but not in the long-term. This is accompanied by a reduction of ~70% in the number of
lymphocytes and an increase in the number of neutrophil granulocytes of ~47% in blood
(Sreerama et al., 2008). However, when calves have been vaccinated against intimin and EspB,
the virulence factors of E. coli O157, significantly higher levels of IgG (~ 4-7 fold, p