Objective—To determine the baseline costs of
bovine leukemia virus (BLV) infection, including costs
of clinical disease and subclinical infection, in a dairy
herd representative of the mid-Atlantic region and
compare these costs with the cost of a test-and-manage
BLV control program.
Design—Stochastic spreadsheet model.
Sample Population—A commercial Holstein dairy
herd with 100 milking cows.
Procedures—A spreadsheet model was developed.
The overall cost of infection included the cost of clinical
disease (ie, lymphosarcoma [LS]) and the effects
of subclinical infection on milk production and premature
culling. Model input values and distributions
were designed to reflect economic conditions in the
mid-Atlantic region. Relative costs of infection and
control were calculated for infection prevalences of
20, 50, and 80%.
Results—Estimated mean cost to the producer per
case of LS was $412; for a herd with a 50% prevalence
of BLV infection, annual incidence of LS was 0.66.
Mean annual cost of subclinical infection at a 50%
prevalence of infection was $6,406. Mean annual cost
of a test-and-manage control program was $1,765. The
cost of clinical disease and subclinical infection varied
substantially with the prevalence of infection, whereas
the cost of control varied with herd size.
Conclusions and Clinical Relevance—Results suggested
that a basic BLV control program may be economically
beneficial in herds in which the prevalence
of BLV infection is ≥ 12.5%. Farm-specific considerations
may factor prominently when weighing the
costs and benefits of an individual BLV control program.
(J Am Vet Med Assoc 2003;223:346–352)
Objective—To determine the association between
serologic status for bovine leukemia virus (BLV) and
culling rates by use of survival times in a commercial
Holstein dairy herd.
Animals—593 milking cows.
Procedure—Cattle were tested for antibodies against
BLV by use of agar gel immunodiffusion or ELISA 4
times each year from 1989 to 1993 and then annually
through 1999. Dates of birth, first calving, and culling
or death were obtained from Dairy Herd Improvement
Association records. Most cows were enrolled in the
study on the date of first calving. Survival times were
compared among seropositive, seronegative, and
seroconverted cows with the Kaplan-Meier method
and a Cox regression model stratified on the basis of
year of birth.
Results—Complete records were available for 593 of
685 (87%) cattle in the dairy herd during the study
period. Median survival time for all cows was 31.7
months. Survival times, which correspond to cull
rates, did not differ significantly between seropositive
and seronegative cattle, whereas cattle that seroconverted
during the study had a significantly longer survival
time. Year of birth was positively and significantly
associated with survival time.
Conclusions and Clinical Relevance—BLV serologic
status was not associated with cull rate as measured
by survival time in this dairy herd. This finding is in
contrast to results of studies that used survival analysis
techniques; our results may influence management
decisions concerning BLV. (J Am Vet Med Assoc
Objective—To compare the temporal and spatial distribution of cases of blastomycosis among humans and dogs in Illinois.
Design—Retrospective cross-sectional survey.
Sample—Human and canine populations in Illinois from 2001 through 2007.
Procedures—For each year, human population data were obtained from the US Census Bureau, and the total number of dogs was estimated by use of a human population-based formula. Data regarding infections with Blastomyces dermatitidis in humans were accessed from the Illinois Department of Public Health. Data regarding B dermatitidis infections in dogs were acquired through a survey of a random sample of the 747 veterinary medical practices in Illinois. Statistical analyses of human and canine data were performed by use of t tests, ANOVA, odds ratio assessment, and regression modeling.
Results—Estimated annual incidence of human cases of blastomycosis in Illinois increased from 3.8 to 10.7 cases/1 million persons/y from 2001 through 2007. Analysis of data from 221 veterinary practices revealed that the mean estimated annual incidence of canine cases of blastomycosis was 8.3 times the mean estimated annual incidence of human cases, with a similar pattern of change and regional distributions. Thirty-eight counties reported either human or canine cases but not both.
Conclusions and Clinical Relevance—The estimated annual incidence of blastomycosis in humans and dogs in Illinois increased during the period of interest. Veterinarians, physicians, and public health agencies should be encouraged to communicate with each other regarding diagnoses of blastomycosis in either species to facilitate early diagnosis and treatment.