Genetic characterization and clinicopathological features of <em>Escherichia coli</em> in neonatal septicemic calves

Abstract

Due to severe diarrhea associated with calf scour and septicemia, colibacillosis is one of the leading causes of neonatal mortality in calves. This study investigated the clinical and hematological manifestations as well as the genetic composition of Shiga toxin-producing E. coli (STEC) strains in septicemic neonatal calves. In this study, 47 fecal specimens were collected from diarrheic calves aged between one and three weeks on dairy farms that are unorganized around Basra, Iraq, while twenty age-matched calves were tested as controls. Of the 47 tested samples, 28 fecal samples were tentatively identified as STEC, with a prevalence of 60%. STEC-affected calves had variable rectal temperatures ranging from subnormal to fever, tachycardia, hyperpnea, diarrhea, partial or complete cessation of suckling, mucous membrane congestion, depression, incoordination and rough hair coat conditions. Significant changes were observed in the hemogram and the leukogram during the analysis of blood samples from calves with diarrhea. Molecular analysis of fecal samples demonstrated that local STEC isolates are more closely related to other strains obtained from both human and animal samples worldwide. Based on the results of the current study, we can conclude that the septicemic calves were likely infected by human or environmental resources and could play a major role in further spreading STEC infection.