Abstract
BackgroundEnterotoxigenic E. coli (ETEC) significantly contribute to diarrhea in piglets and weaners. The smallholder pig producers in Uganda identified diarrhea as one of the major problems especially in piglets. The aim of this study was to; i) characterize the virulence factors of E. coli strains isolated from diarrheic and non-diarrheic suckling piglets and weaners from smallholder herds in northern and eastern Uganda and ii) identify and describe the post-mortem picture of ETEC infection in severely diarrheic piglets. Rectal swab samples were collected from 83 piglets and weaners in 20 herds and isolated E. coli were characterized by PCR, serotyping and hemolysis.ResultsThe E. coli strains carried genes for the heat stable toxins STa, STb and EAST1 and adhesins F4 and AIDA-I. The genes for the heat labile toxin LT and adhesins F5, F6, F18 and F41 were not detected in any of the E. coli isolates. Where the serogroup could be identified, E. coli isolates from the same diarrheic pig belonged to the same serogroup. The prevalence of EAST1, STb, Stx2e, STa, AIDA-I, and F4 in the E. coli isolates from suckling piglets and weaners (diarrheic and non-diarrheic combined) was 29, 26.5, 2.4, 1.2, 16, and 8.4 %, respectively. However the prevalence of F4 and AIDA-I in E. coli from diarrheic suckling piglets alone was 22.2 and 20 %, respectively. There was no significant difference in the prevalence of the individual virulence factors in E. coli from the diarrheic and non-diarrheic pigs (p > 0.05). The main ETEC strains isolated from diarrheic and non-diarrheic pigs included F4/STb/EAST1 (7.2 %), F4/STb (1.2 %), AIDA/STb/EAST1 (8 %) and AIDA/STb (8 %). At post-mortem, two diarrheic suckling piglets carrying ETEC showed intact intestinal villi, enterocytes and brush border but with a layer of cells attached to the brush border, suggestive of ETEC infections.ConclusionThis study has shown that the F4 fimbriae is the most predominant in E. coli from diarrheic piglets in the study area and therefore an F4-based vaccine should be considered one of the preventive measures for controlling ETEC infections in the piglets in northern and eastern Uganda.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0796-2) contains supplementary material, which is available to authorized users.
Highlights
Enterotoxigenic E. coli (ETEC) significantly contribute to diarrhea in piglets and weaners
In 2007, another non-fimbrial adhesion called porcine attaching and effacing-associated factor that was originally identified in enteropathogenic E. coli strains was suggested to play a big role in the pathogenesis of Enterotoxigenic Escherichia coli (ETEC) infections [22] and recently, paa was reported to be associated with F4-positive ETEC from diarrheic piglets [23]
This study reported isolation of ETEC strains and presence of ETEC diarrhea in piglets and /or weaners from smallholder herds
Summary
Enterotoxigenic E. coli (ETEC) significantly contribute to diarrhea in piglets and weaners. The ETEC contribute to or cause diarrhea by first adhering to host receptors in the brush border of enterocytes in the duodenum, jejunum and /or ileum using adhesins [12], and secondly by producing toxins that when absorbed, cause efflux of water and electrolytes into the intestinal lumen and /or reduced intestinal absorption [13,14,15]. In 2007, another non-fimbrial adhesion called porcine attaching and effacing-associated factor (paa) that was originally identified in enteropathogenic E. coli strains was suggested to play a big role in the pathogenesis of ETEC infections [22] and recently, paa was reported to be associated with F4-positive ETEC from diarrheic piglets [23]. Knowledge about prevalent adhesins has been employed to prepare anti-adhesin vaccines for control of ETEC infections through the vaccination of sows before parturition, enabling the piglets to acquire passive immunity through colostrum [30, 31]
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