Evaluate the expression of four virulence factors (fedA, faeG, eae and toxA from Escherichia coli) by using qPCR. toxA, coding for the heat-labile enterotoxin (LT); eae, coding for the intimine; fedA, coding for the F18 fimbriae and faeG, coding for the F4 fimbriae. Post-weaning diarrhea is an important enteric disease that usually occurs shortly after weaning and is characterized by watery diarrhea, dehydration, loss of body weight, and the death of infected pigs. This diarrhea is responsible for important economic losses due to mortality, morbidity, decreased growth rate and cost of medication. Escherichia coli is one of the most important causes of the increasing worldwide outbreaks of post-weaning diarrhea, causing sudden death or severe diarrhoea. The PCR identification of virulence factors of E. coli from fecal samples is normally used for the diagnosis of pathogenic isolates.