Molecular characterization of Enterotoxigenic <em>Escherichia coli </em> (ETEC) isolated from intestinal tissues of diarrhoeic neonatal piglets on commercial farms in Ogun State, Nigeria

Context: Neonatal colibacillosis, caused by enterotoxigenic Escherichia coli (ETEC), is an important disease in pigs that leads to economic losses in commercial farming and threatens the development of the pig industry and food security. Aim: This study aimed to carry out the molecular characterization of the enterotoxin genes, particularly heat-labile (LT) and heat-stable (STa and STb), of ETEC isolated from intestinal tissues of neonatal piglets that died of diarrhoea on a commercial pig farm estate in Ogun State, Nigeria. Methods: Biochemically confirmed isolates of E. coli were subjected to multiplex polymerase chain reaction (PCR) assay to detect enterotoxin genes. Three amplicons were sequenced and a phylogeny analysis was performed. Results: Of the 60 bacterial isolates, 34 (56%) were E. coli. The prevalence of ETEC strains was 26.5%, attributed solely to the heat-stable STa toxin gene. Phylogenetic analysis showed that the Nigerian strain is genetically closest to European ETEC strains, especially from Belgium and the Netherlands, and is most likely responsible for the associated pathogenicity and neonatal piglet diarrhoea and mortality in Nigeria. Conclusions: This finding is important for understanding the cause of neonatal piglet deaths in the study area and for informing the development of vaccines to protect against ETEC diarrhoea for use in piglets and other farm animals in Nigeria.