Shiga toxin-producing Escherichia coli (STEC) from Farm Animals and Humans in Tropical Africa - A review

Abstract

The study was designed to review the incidences and characteristics of Shiga toxin-producing Escherichia coli (STEC) from farm animals and humans in tropical Africa. Serotypes O157, O26, O103, O91, O45 and O111 are usually associated with public health risks, and these serotypes are most frequently isolated from food animals. The main virulent factors of STEC associated with human diseases are potent cytotoxins (shiga toxins [stx] stx1 and stx2), which are encoded by the stx1 and stx2 genes. Two additional markers also play a role in the pathogenesis of Hemorrhagic colitis (HC) and Hemolytic Uremic Syndrome (HUS): an outer membrane protein (intimin), encoded by the eae gene, and enterohaemolysin, encoded by the ehlyA gene. All age groups of animals and humans can be infected with STEC, but young animals and children, the elderly, and those with compromised immune systems are the most severely affected. Little is known about factors that determine susceptibility to STEC infection and the risk factors for the development of systemic complications such as HUS. The peak age incidences (infants and young children) of classical HUS is a reflection of the age incidences of STEC infection as a whole, suggesting that susceptibility to STEC-associated HUS may, like other specific infectious diseases of childhood, be due to the lack of specific immunity, possibly to ST. The increasing recognition of STEC-associated HUS in the elderly would be consistent with waning immunity in that age group. There should be sensitization and awareness regards to the incidences and distribution of STEC serogroups O157, O26, O45, O91, O103 and O111 which are associated with public health risks in livestock and humans in tropical Africa and some parts of the world.