Did they analyze the moisture content for fresh vs dried fecal matter? Especially for cattle patties? Was it surface cured-dry exterior vs thoroughly dried? How did teams assess or quantify?
We did not measure moisture content. Our designation of fresher and drier was relatively subjective based on the perceived level of dryness and pliability of the fecal material while manually handling the material.
Do we know why cattle seem to peak in positives in late summer?
At this time, we do not know definitively why the prevalence of STEC infection was higher in summer and fall compared to spring.
Have vaccines been developed for O157 in cattle? I don't like the idea but I am curious.
Yes, there are vaccines for E. coli O157:H7 that appear to reduce the prevalence and/or intensity of infection, but given that enteric infection in adult cattle are generally non-clinical for this bacterium, there may be limited interest among ranchers to vaccinate their cattle. In addition, these vaccines need to be given more than once which limits their practicality for a commercial ranching operation.
In the longitudinal study, did positive detections tend to appear as isolated events or as clusters within certain time windows or ranches?
In general, when a novel strain of STEC was detected on a ranch in livestock feces or wildlife scat, it was observed as a cluster of positive samples in both cattle and wildlife. These clustered events were typically transient, with subsequent sampling over the following months yielding negative fecal cultures. However, exceptions were observed. In some cases, only one or or a few fecal samples tested positive on a property, suggesting limited transmission or persistence of STEC within livestock and wildlife populations.
In the positives on the cattle that showed up and then disappeared - were any treatments done on the cattle that would contribute to its disappearance? Were weather events thought to contribute?
We do not have a provable explanation for why the cattle would become infected with a specific strain of STEC and then months later appear to be non-infected based on negative fecal culture. In experimental studies where we inoculate cattle with specific doses of specific strains of E. coli O157:H7, we do observe a limited duration of fecal shedding in the experimentally infected cattle. This observation suggests that cattle, absent of any veterinary medical intervention or treatments, can clear the enteric infection or alternatively shed at undetectable fecal concentrations.
It is understood that young cattle shed E. coli more frequently than adults, and also more when the weather is warm. Was there any correlation to warmer weather and calving season (more young cattle)?
We did not specifically evaluate correlations with temperature or calving season (i.e., the presence of young cattle). However, we observed that the prevalence of non-O157 STEC in livestock was significantly higher in fall (highest), followed by summer and winter, compared to spring. While seasonal differences were evident, our data do not allow us to attribute these patterns directly to warmer weather or the presence of young cattle. We will include weather conditions—such as mean air temperature, relative humidity, and other relevant variables—averaged over the 7 days prior to sampling for future in-depth analyses or manuscript.
On the clusters of acute infection, where there is presence of infection in livestock it seemed there is often presence in wildlife. Any inclination on who infects who?
We can only speculate as to which population infects the other. The livestock at the study locations are generally fenced while the wildlife can generally move more freely across the landscape and between study locations.
Was there any further breakdown with regards to the livestock operation size and prevalence of STEC?
We are still analyzing the various potential risk factors, such as herd size, for their association with herd prevalence of STEC.
Were any questions asked of cow calf operations or compost operations on best management practices? If so, was there any correlation to best practices in place and negatives or positives found?
Assessing relationships between STEC detection and best management practices (BMPs) was not an objective of this study. BMP information was not systematically collected, and therefore correlations between management practices and STEC-positive or -negative samples were not evaluated.
Were the ranch locations adjacent to one another? In the table showing O157 on properties, was R1 next to R2, curious if wildlife traffic patterns played a role in the occurrences between the location.
The ranches were not located adjacent to each other; instead, they were located throughout the Central California Coastal study region, ranging mostly from northern and southern Monterey County and San Benito County, but also south of these county locations.
When a strain "blossoms" on a cattle ranch, is that because it was introduced or the environment changed so that particular bacteria that was latent in very low numbers grew tremendously in number?
We can only speculate as to the mechanism(s) causing the sudden appearance of a novel strain of STEC at a livestock ranch. One explanation would be the novel strain was introduced by infected free-ranging wildlife entering the property and infecting susceptible cattle and wildlife. Alternatively, the rancher purchased one or more infected replacement animals. It is also possible environmental or animal conditions changed such that a latent enteric infection became active and replicated to such an extent that fecal detection suddenly occurred.