Objective—To evaluate the antimicrobial susceptibility
patterns of Salmonella isolates from feedlot cattle.
Sample Population—263 Salmonella isolates.
Procedures—Fecal samples were collected from the
floor of 2 pens in each of 100 feedlots. Two hundred
eighty Salmonella isolates were recovered after bacteriologic
culture from 38 pens. Of these, 263 isolates
were available for antimicrobial susceptibility testing
to 16 antimicrobials, using microbroth dilution breakpoint
Results—Less than 5% of isolates were resistant to
any of the antimicrobials tested, with the exception of
sulfamethoxazole (15; 5.7%) and tetracycline (61;
23.2%). Most isolates (197; 74.9%) were susceptible
to all antimicrobials tested, whereas 18 (6.8%) were
resistant to 2 or more antimicrobials. The percentage
of isolates with resistance to any antimicrobial varied
by serotype. The percentage of isolates resistant to
various antimicrobials was not related to concurrent
use of antimicrobials in the feed.
Conclusions and Clinical Relevance—With the
exception of tetracycline and sulfamethoxazole, resistance
of Salmonella isolates to any of the antimicrobials
was uncommon. Most isolates were susceptible
to all antimicrobials tested. Antimicrobial resistance
was not related to the presence of antimicrobials in
the ration being fed at the time of sample collection.
(J Am Vet Med Assoc 2002;221:268–272)
Objective—To evaluate knowledge, attitudes, and management practices involving antimicrobial use among Tennessee beef producers.
Sample Population—A population-based, stratified random sample of 3,000 beef producers across the state.
Procedures—Questionnaires were mailed to beef producers. Questions focused on producer practices related to education, biosecurity, veterinary use, and the purchase and use of antimicrobials. Operation types were categorized as either cow-calf only or multiple operation type (MOT). Associations between various factors and antimicrobial use were evaluated by use of multivariable logistic regression, with the outcome variable being any antimicrobial use (injectable or by mouth) in the past year.
Results—Of 3,000 questionnaires mailed, 1,042 (34.7%) were returned. A significantly higher proportion of producers with MOTs reported giving antimicrobials by mouth or by injection than did producers with cow-calf only operations. In addition, higher proportions of producers with MOTs than producers with cow-calf only operations reported treating with macrolides, florfenicol, ceftiofur, and aminoglycosides. In the multivariable analysis, herd size >50 cattle, participation in Beef Quality Assurance or master beef producer certification programs, quarantining of newly purchased animals, use of written instructions for treating disease, and observation of withdrawal times were associated with a higher likelihood of antimicrobial use.
Conclusions and Clinical Relevance—Results suggested that producers who engaged in more progressive farming practices were also more likely to use antimicrobials. Incorporating training on judicious antimicrobial use into educational programs would likely increase awareness of best management practices regarding antimicrobial use.
Objective—To estimate the annual cost of infections
attributable to porcine reproductive and respiratory syndrome
(PRRS) virus to US swine producers.
Sample Population—Data on the health and productivity
of PRRS-affected and PRRS-unaffected breeding
herds and growing-pig populations were collected
from a convenience sample of swine farms in the
midwestern United States.
Procedure—Health and productivity variables of
PRRS-affected and PRRS-unaffected swine farms
were analyzed to estimate the impact of PRRS on
specific farms. National estimates of PRRS incidence
were then used to determine the annual economic
impact of PRRS on US swine producers.
Results—PRRS affected breeding herds and growing-pig
populations as measured by a decrease in reproductive
health, an increase in deaths, and reductions
in the rate and efficiency of growth. Total annual economic
impact of these effects on US swine producers
was estimated at $66.75 million in breeding herds and
$493.57 million in growing-pig populations.
Conclusions and Clinical Relevance—PRRS imposes
a substantial financial burden on US swine producers
and causes approximately $560.32 million in
losses each year. By comparison, prior to eradication,
annual losses attributable to classical swine fever
(hog cholera) and pseudorabies were estimated at
$364.09 million and $36.27 million, respectively
(adjusted on the basis of year 2004 dollars). Current
PRRS control strategies are not predictably successful;
thus, PRRS-associated losses will continue into
the future. Research to improve our understanding of
ecologic and epidemiologic characteristics of the
PRRS virus and technologic advances (vaccines and
diagnostic tests) to prevent clinical effects are warranted.
(J Am Vet Med Assoc 2005;227:385–392)
Objective—To evaluate herd-level risk factors for
seropositive status of cattle to 1 or more bluetongue
Animals—110 herds of cattle in Nebraska, North
Dakota, and South Dakota.
Procedure—Blood samples were collected before
and after the vector season. Samples were tested
for antibodies against bluetongue virus by use of a
commercially available competitive ELISA. Factors
evaluated included descriptors of geographic location
and management practices. Trapping of insect
vectors was conducted to evaluate vector status on
a subset of 57 operations. A multivariable logistic
regression model was constructed to evaluate associations.
Results—For the full data set, altitude and latitude
were associated with risk of having seropositive cattle
(an increase in altitude was associated with an
increase in risk, and a more northerly location was
associated with a decrease in risk of a premise having
seropositive cattle). Import of cattle from selected
states was associated with an increase in risk of having
seropositive cattle. From the subset of herds with
data on vector trapping, altitude and latitude were
associated with risk of having seropositive cattle, similar
to that for the full model. However, commingling
with cattle from other herds was associated with a
decrease in risk of seropositivity.
Conclusions and Clinical Relevance—Findings
reported here may be useful in generating additional
hypotheses regarding the ecologic characteristics of
bluetongue viruses and other vector-borne diseases
of livestock. Sentinel surveillance programs are useful
for documenting regionalization zones for diseases,
which can be beneficial when securing international
markets for animals and animal products. (Am J Vet