Objective—To develop a spatial epidemic model to
simulate intraherd and interherd transmission of footand-
mouth disease (FMD) virus.
Sample Population—2,238 herds, representing
beef, dairy, swine, goats, and sheep, and 5 sale yards
located in Fresno, Kings, and Tulare counties of
Procedure—Using Monte-Carlo simulations, a spatial
stochastic epidemic simulation model was developed
to identify new herds that would acquire FMD following
random selection of an index herd and to assess
progression of an epidemic after implementation of
mandatory control strategies.
Results—The model included species-specific transition
periods for FMD infection, locations of herds,
rates of direct and indirect contacts among herds, and
probability distributions derived from expert opinions
on probabilities of transmission by direct and indirect
contact, as well as reduction in contact following
implementation of restrictions on movements in designated
infected areas and surveillance zones.
Models of supplemental control programs included
slaughter of all animals within a specified distance of
infected herds, slaughter of only high-risk animals
identified by use of a model simulation, and vaccination
of all animals within a 5- to 50-km radius of infected
Conclusions and Clinical Relevance—The FMD
model represents a tool for use in planning biosecurity
and emergency-response programs and in comparing
potential benefits of various strategies for control
and eradication of FMD appropriate for specific populations.
(Am J Vet Res 2003;64:195–204)
Objective—To assess estimated effectiveness of
control and eradication procedures for foot-andmouth
disease (FMD) in a region of California.
Sample Population—2,238 herds and 5 sale yards in
Fresno, Kings, and Tulare counties of California.
Procedure—A spatial stochastic model was used to
simulate hypothetical epidemics of FMD for specified
control scenarios that included a baseline eradication
strategy mandated by USDA and supplemental control
strategies of slaughter or vaccination of all animals within
a specified distance of infected herds, slaughter of
only high-risk animals identified by use of a model simulation,
and expansion of infected and surveillance zones.
Results—Median number of herds affected varied
from 1 to 385 (17% of all herds), depending on type
of index herd and delay in diagnosis of FMD.
Percentage of herds infected decreased from that of
the baseline eradication strategy by expanding the
designated infected area from 10 to 20 km (48%),
vaccinating within a 50-km radius of an infected herd
(41%), slaughtering the 10 highest-risk herds for each
infected herd (39%), and slaughtering all animals
within 5 km of an infected herd (24%).
Conclusions and Clinical Relevance—Results for the
model provided a means of assessing the relative merits
of potential strategies for control and eradication of
FMD should it enter the US livestock population. For the
study region, preemptive slaughter of highest-risk herds
and vaccination of all animals within a specified distance
of an infected herd consistently decreased size and
duration of an epidemic, compared with the baseline
eradication strategy. (Am J Vet Res 2003;64:205–210)
Objective—To assess relative costs and benefits of
vaccination and preemptive herd slaughter to control
transmission of foot-and-mouth disease (FMD) virus
Sample Population—2,238 herds and 5 sale yards
located in Fresno, Kings, and Tulare counties of
Procedure—Direct costs associated with indemnity,
slaughter, cleaning and disinfecting livestock premises,
and vaccination were compared for various eradication
strategies. Additional cost, total program cost,
net benefit, and benefit-cost value (B/C) for each supplemental
strategy were estimated, based in part on
results of published model simulations for FMD.
Sensitivity analyses were conducted.
Results—Mean herd indemnity payments were estimated
to be $2.6 million and $110,359 for dairy and
nondairy herds, respectively. Cost to clean and disinfect
livestock premises ranged from $18,062 to
$60,205. Mean vaccination cost was $2,960/herd.
Total eradication cost ranged from $61 million to $551
million. All supplemental strategies involving use of
vaccination were economically efficient (B/C range,
5.0 to 10.1) and feasible, whereas supplemental
strategies involving use of slaughter programs were
not economically efficient (B-C, 0.05 to 0.8) or feasible.
Conclusions and Clinical Relevance—Vaccination
with a highly efficacious vaccine may be a cost-effective
strategy for control of FMD if vaccinated animals
are not subsequently slaughtered and there is no
future adverse economic impact, such as trade
restrictions. Although less preferable than the baseline
eradication program, selective slaughter of highest-risk herds was preferable to other preemptive
slaughter strategies. However, indirect costs can be
expected to contribute substantially more than direct
costs to the total cost of eradication programs. (Am J Vet Res 2003;64:805–812)
Objective—To estimate direct and indirect contact
rates on livestock facilities and distance traveled
between herd contacts.
Sample Population—320 beef, dairy, goat, sheep,
and swine herds, 7 artificial insemination technicians,
6 hoof trimmers, 15 veterinarians, 4 sales yard owners,
and 7 managers of livestock-related companies
within a 3-county region of California.
Procedure—A questionnaire was mailed to livestock
producers, and personal and telephone interviews
were conducted with individuals.
Results—Mean monthly direct contact rates were
2.6, 1.6, and 2.0 for dairies with < 1,000, 1,000 to
1,999, and ≥ 2,000 cattle, respectively. Mean indirect
contact rates on dairies ranged from 234 to 743 contacts/
mo and increased by 1 contact/mo as herd size
increased by 4.3. Mean direct monthly contact rate
for beef herds was 0.4. Distance traveled by personnel
and vehicles during a 3-day period ranged from
58.4 to 210.4 km. Of livestock arriving at sales yards,
7% (500/7,072) came from ≥ 60 km away, and of
those sold, 32% (1,180/3,721) were destined for a
location ≥ 60 km away. Fifty-five percent (16/29) of
owners of large beef herds observed deer or elk within
150 m of livestock at least once per month.
Conclusions and Clinical Relevance—Direct and
indirect contacts occur on livestock facilities located
over a wide geographic area and at a higher frequency
on larger facilities. Knowledge of contact rates may
be useful for planning biosecurity programs at the
herd, state, and national levels and for modeling
transmission potential for foot-and-mouth disease
virus. (Am J Vet Res 2001;62:1121–1129)
Objective—To determine the lowest of 5 doses of cosyntropin (1.0, 0.5, 0.1, 0.05, or 0.01 μg/kg) administered IV that stimulates maximal cortisol secretion in clinically normal dogs.
Animals—10 clinically normal dogs.
Procedures—5 dose-response experiments were performed in each of the dogs. Each dog received 5 doses of cosyntropin (1.0, 0.5, 0.1, 0.05, and 0.01 μg/kg) IV in random order (2-week interval between each dose). Serum samples for determination of cortisol concentrations were obtained before (baseline) and at 10, 20, 30, 40, 50, 60, 120, and 240 minutes after cosyntropin administration.
Results—Compared with baseline values, mean serum cortisol concentration in the study dogs increased significantly after administration of each of the 5 cosyntropin doses. Mean peak serum cortisol concentration was significantly lower after administration of 0.01, 0.05, and 0.1 μg of cosyntropin/kg, compared with findings after administration of 0.5 and 1.0 μg of cosyntropin/kg. After administration of 0.5 and 1.0 μg of cosyntropin/kg, mean peak serum cortisol concentration did not differ significantly; higher doses of cosyntropin resulted in more sustained increases in serum cortisol concentration, and peak response developed after a longer interval.
Conclusions and Clinical Relevance—Administration of cosyntropin IV at a dose of 0.5 μg/kg induced maximal cortisol secretion in healthy dogs. Serum cortisol concentration was reliably increased in all dogs after the administration of each of the 5 doses of cosyntropin. These data should be useful in subsequent studies to evaluate the hypothalamic-pituitary-adrenal axis in healthy and critically ill dogs.