Objective—To evaluate fecal shedding of Giardia duodenalis,
Cryptosporidium parvum, Salmonella organisms,
and Escherichia coli O157:H7 from llamas in
California with respect to host factors and management
Animals—354 llamas from 33 facilities.
Procedure—Fecal specimens were collected and
examined for G duodenalis and C parvum by means
of immunofluorescent microscopy. Salmonella organisms
were cultured by placing feces into selenite
enrichment broth followed by selective media.
Escherichia coli O157:H7 was cultured by use of modified
tryptocase soy broth followed by sorbitol
MacConkey agar, with suspect colonies confirmed by
means of immunofluorescent microscopy.
Results—12 of 354 fecal specimens (3.4%) had G
duodenalis cysts. Younger llamas (crias) were more
likely to be shedding cysts, compared with older llamas.
Farm-level factors that increased the risk of
shedding were large numbers of yearlings on the
property (> 10), smaller pen sizes, large numbers of
crias born during the previous year (> 10), and large
pen or pasture populations (> 20). None of the 354
fecal specimens had C parvum oocysts. Seventy-six
(from 7 facilities) and 192 (from 22 facilities) llamas
were tested for Salmonella organisms and E coli
O157:H7, respectively. All fecal specimens had negative
results for these bacteria.
Conclusion and Clinical Relevance—Shedding of
G duodenalis was primarily limited to crias 1 to 4
months old. Llamas from properties with large numbers
of crias born in the previous year, resulting in
large numbers of yearlings in the current year, were at
greater risk of infection. In addition, housing llamas in
smaller pens or pastures and managing llamas and
crias in large groups also increased the risk of G duodenalis shedding.
(Am J Vet Res 2001;62:637–642)
Objective—To evaluate seasonal patterns and risk factors for Escherichia coli O157:H7 in feces in a beef cattle herd and determine strain diversity and transition in E coli over time by use of multiple-locus variable-number tandem-repeat analysis (MLVA) and pulsed-field gel electrophoresis (PFGE).
Sample Population—456 samples of freshly passed feces collected over a 1-year period from cattle in a range-based cow-calf operation located in the foothills of the Sierra Nevada Mountains in California.
Procedures—E coli O157:H7 was recovered from feces by use of immunomagnetic separation and 2 selective media. Virulence factors were detected via reverse transcriptase-PCR assay. Escherichia coli O157:H7 isolates were subtyped with MLVA and PFGE. Prevalence estimates were calculated and significant risk factors determined. A dendrogram was constructed on the basis of results of MLVA typing.
Results—Overall prevalence estimate for E coli O157:H7 was 10.5%, with the prevalence lowest during the winter. Mean temperature during the 30 days before collection of samples was significantly associated with prevalence of E coli O157:H7 in feces. Nineteen MLVA and 12 PFGE types were identified.
Conclusions and Clinical Relevance—A seasonal pattern was detected for prevalence of E coli O157:H7 in feces collected from beef cattle in California. Subtyping via MLVA and PFGE revealed a diversity of E coli O157:H7 strains in a cow-calf operation and noteworthy turnover of predominant types. Given the importance of accurately determining sources of contamination in investigations of disease outbreaks in humans, MLVA combined with PFGE should be powerful tools for epidemiologists. (Am J Vet Res 2010;71:1339–1347)
Objective—To elucidate the ecology of Listeria monocytogenes on dairy cattle farms by determining the prevalence of the organism in various samples.
Sample Population—Dairy cattle operations in central New York State.
Procedures—A repeated cross-sectional study design was used. Various samples were obtained from cattle (feces, composite udder milk, and udders), their environment (silage, feed bunks, water troughs, and floor bedding), inline milk filters, and bulk tank milk from 50 dairy farms. Samples were tested for L monocytogenes by use of a PCR assay with 2 steps of bacterial enrichment. Data were analyzed with mixed-effect logistic regression to control for the potential clustering of L monocytogenes on particular farms.
Results—L monocytogenes was detected in composite milk, udder swab samples, and fecal samples at prevalences of 13%, 19%, and 43%, respectively. There was no significant clustering of the pathogen by farm. Listeria monocytogenes was more common in samples obtained from cattle and the environment during winter and summer versus the fall. The prevalence of L monocytogenes was twice as high in samples obtained from feed bunks, water troughs, and bedding, compared with that in samples obtained from silage (65%, 66%, 55%, and 30%, respectively).
Conclusions and Clinical Relevance—L monocytogenes was more prevalent in samples obtained from dairy cattle and their environment than in milk samples. Strategies to control the pathogen in dairy operations should focus on cow hygiene and sanitary milk harvesting on the farm.