Verotoxigenic E. coli in a goat herd.
Murray Hazlett, Jennifer Hanmore, Durda Slavic
A herd of dairy goats comprised of ~ 140 milking does, 130 doelings, and 160 kids experienced an outbreak of scours in the kids. All kids were housed in the same area in groups of 8-10 animals. This was the first outbreak of scours on the farm and there had been no recent introductions. There were no cattle on the farm. The diarrhea was usually very watery, although one animal that died had pasty/congealed feces with no blood noted. Most of the kids were ~ 10-d-old when the scours started, which lasted about 2 wk. Nine kids died. About 20% of the kids were affected, some with less severe clinical signs. The producer started the kids on an over-the-counter mixture of oral streptomycin/penicillin G with vitamin mixture and no additional animal became sick.
Two poor-doing 10-d-old kids were autopsied immediately after death with samples collected for histology and microbiology. Histologically, there were large numbers of both small bacilli (Fig. 1A) and, in some areas, gram-positive cocci could be seen adherent to enterocytes in both small intestine and colon sections. There was attenuation and exfoliation of luminal/superficial enterocytes, with occasional small aggregates of neutrophils in the superficial lamina propria. In one kid, there was edema with mild diffuse neutrophilic inflammation in the colonic submucosa.
A fecal floatation and PCR testing for bovine rotavirus and coronavirus were negative. E. coli was isolated in moderate numbers, along with Clostridium perfringens type A and Enterococcus durans. The E. coli was considered verotoxigenic, demonstrating genes for intimin and Shiga toxin type 1 as well as enterohemolysin. Testing for other genes, including for enterotoxigenic E coli, was negative.
Verotoxigenic E. coli has been identified in normal cattle, sheep, and goats, which can serve as reservoirs for this pathogen. In our case, it was felt to be significant based on the lesions seen in association with the large numbers of small gram-negative bacilli colonizing the brush border in areas of enterocyte exfoliation (Fig. 1B). We also identified Enterococcus durans in this case; its significance in diarrhea is uncertain – it has been associated with diarrhea in pigs and calves, and may also have contributed in our case.
A review of AHL pathology computer records (2008–2018) revealed 20 diagnoses of enteritis associated with E. coli in goats. Of these, where supportive bacteriology was done (12 cases), 3 were identified as enterotoxigenic E coli (ETEC - K99 +ve), 4 as enteropathogenic E coli (EPEC - with adhesion genes but no shiga toxin), and 5 as verotoxigenic E coli (VTEC - both intimin and a shiga toxin gene identified). VTEC +ve cases were 7-14-d-old. No other pathogens were identified or felt to be involved in the VTEC cases except for cryptosporidia in one case. AHL
Figure 1. A. Plump bacilli (arrow) attached to an exfoliating enterocyte. B. Gram (Brown and Hopps) stain showing gram-negative bacilli (arrow) heavily colonizing the surface of enterocytes.