Intermittent and persistent shedding of Escherichia coli O157 in cohorts of naturally infected calves.
OBJECTIVE
We conducted two short-term studies of cohorts of naturally infected calves to determine the prevalence and concentrations of Escherichia coli O157 shed in faeces.


RESULTS
Two cohorts of calves were sampled; in the first study 14 calves were sampled up to five times a day for 5 days; in the second study a group of 16 separate calves were sampled once or twice a day for 15 days. All cattle within the two cohorts shed E. coli O157 at some point during the respective studies. In 18% of samples, E. coli O157 could only be isolated using immunomagnetic separation after an enrichment period, suggesting concentrations <250 CFU g(-1). The highest concentrations recorded were 6.7 x 10(5) and 1.6 x 10(6) CFU g(-1) for studies 1 and 2 respectively.


CONCLUSIONS
Persistent, high shedders (shedding >10(3) CFU g(-1)) were evident in both studies but, in the majority of calves, the pathogen was isolated intermittently.


CONCLUSIONS
The variable patterns of shedding have important implications for the design of appropriate sampling protocols and for gaining meaningful estimates of parameters used in mathematical models of transmission.
Robinson
S E
SE
DEFRA Epidemiology Fellowship Unit, University of Liverpool, South Wirral, UK. s.e.robinson@liv.ac.uk
Wright
E J
EJ
Hart
C A
CA
Bennett
M
M
French
N P
NP
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D015331:Cohort Studies; D015169:Colony Count, Microbial; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D008297:Male; D013048:Specimen Handling / Q000379:methods