Objectives—To determine historical events leading to establishment of bovine tuberculosis in the white-tailed deer population in the northeastern corner of the lower peninsula (NELP) of Michigan and describe factors relevant to the present outbreak of bovine tuberculosis in Michigan.
Sample Population—Cattle and white-tailed deer in Michigan from 1920 to 1990.
Procedures—A search of extant historical documents (eg, scientific journals, books, public reports, and correspondence and internal reports from governmental agencies) was conducted. Factors investigated included the number of cattle and prevalence of tuberculosis, deer population and density levels, and changes in regional environments affecting the population and management of cattle and wild deer.
Results—High deer numbers and severe winter feed shortages resulting from habitat destruction in the NELP in 1930 contributed to the transmission of tuberculosis from cattle to deer. Starvation increased the susceptibility of deer to infection and modified behavior such that exposure to infected cattle was increased. Relocation of deer resulted in spread of infection to other sites, including locations at which spatial clusters of tuberculosis presently exist. Ribotyping of Mycobacterium bovis from a human patient suggests that the strain of M bovispresently infecting white-tailed deer in the region is the same strain that affected cattle farms at that time.
Conclusions and Clinical Relevance—Feeding deer to maintain numbers above the normal carrying capacity of the NELP led to deer depending on consumption of livestock feed for survival during winter and increased contact with domestic cattle. This practice should be avoided.
Objective—To determine prevalence of heartworm
infection among healthy, client-owned cats in the
lower peninsula of Michigan.
Design—Cross-sectional prevalence study.
Animals—1,348 healthy cats examined at private veterinary
practices throughout the lower peninsula of
Procedure—Sera were tested by use of an ELISAbased
antigen test kit to determine infection and 2
commercially available antibody detection kits to
determine exposure. A questionnaire was used to collect
data to assess risk factors associated with infection.
Results—25 cats had positive results for heartworm
antigen, yielding an observed prevalence of 1.9%.
Neither antibody test was reliable or provided reproducible
results, and neither yielded positive results for
more than 20% of the antigen-positive heartworminfected
cats. Multivariate regression indicated that
cats from southeastern Michigan and cats ≥ 2 years
old had a higher risk of infection.
Conclusions and Clinical Relevance—Results indicated
that most (80%) heartworm-infected cats in the
lower peninsula of Michigan were from the southeastern
part of the state, a pattern that closely paralleled
the prevalence of heartworm infection in dogs.
Therefore, knowledge of the regional prevalence of
heartworm infection in dogs may be useful in assessing
the risk of infection in cats. Results also suggested
that currently available in-clinic heartworm antibody
detection kits have limited utility in the diagnosis
of heartworm infection in cats. (J Am Vet Med
Objective—To identify stakeholders who should be included in a Michigan-based avian influenza surveillance system (AISS) and to describe their avian influenza (AI) surveillance and reporting needs.
Design—Cross-sectional survey involving a convenience sample of respondents.
Sample—272 federal, state, and local governmental and regulatory agency professionals; veterinarians and laboratory professionals in academia; private practice veterinarians; and poultry industry members.
Procedures—A needs assessment survey that focused on stakeholder identification, current surveillance methods, information sharing, and desired AISS enhancements was administered by mail, and responses were summarized.
Results—Various AISS stakeholders were identified, among whom the requirements for surveillance information and methods of reporting (including via a World Wide Web-based database, e-mail, and a website) differed. Although 90% of all respondent types indicated that poultry industry representatives were key stakeholders, < 33% of poultry industry respondents indicated that private practice veterinarians and personnel in laboratories or public agencies should be considered stakeholders. The predominant concern (55.4% of respondents) regarding the current AISS was the effectiveness of communication among agencies, industry, and the public. The primary challenge identified by respondents was confidentiality (30.2% of respondents).
Conclusions and Clinical Relevance—In Michigan—and potentially in other regions of the United States—integration of Internet-related data systems and stakeholder communication is likely to promote earlier identification of AI, achieve more effective responses to outbreaks, reduce morbidity among humans and other animals, and decrease outbreak-associated financial losses. Stakeholder education and technological safeguard assurances will be essential in AISS enhancement.
Objective—To determine the efficacy a modified-live Salmonella Dublin vaccine administered PO in an extralabel manner in the prevention of diseases associated with Salmonella Dublin infection.
Design—Randomized clinical trial.
Animals—288 preweaned Holstein dairy calves on a commercial dairy farm.
Procedures—Calves were orally administered either 2 mL of a commercially available, modified-live Salmonella Dublin vaccine (n = 140) or a placebo (148) at 3 and 10 days of age. Signs of diarrhea and depression were recorded daily. Weight gain between 3 days of age and time of weaning was measured. Fecal samples from clinically depressed or diarrheic calves and fresh tissues samples from calves that died were submitted for bacterial culture of Salmonella organisms.
Results—Salmonella organisms were isolated from samples of 1.4% (2/140) and 3.4% (5/148) of calves receiving the vaccine and placebo, respectively. Additionally, 57.1% (80/140) and 60.1 % (89/148) of the vaccinated and control calves, respectively, had at least 1 day with an abnormal fecal score. Calves receiving the vaccine and placebo were not significantly different in terms of overall morbidity rate, Salmonella-specific morbidity rate, or average daily gain. Adverse reactions related to administration of the vaccine were not seen. The attenuated vaccine strain was not isolated from any fecal or tissue samples.
Conclusions and Clinical Relevance—This method of vaccination was safe in young Holstein calves, although it was not effective in reducing the incidence of disease or improving weight gain on this farm. However, the power of this study was limited by a low incidence of clinical salmonellosis.
OBJECTIVE To determine the survivability of Mycobacterium bovis on salt and salt-mineral blocks in typical weather conditions in Michigan over two 12-day periods at the height of summer and winter.
SAMPLE 4 salt (NaCl) and 4 salt-mineral blocks inoculated with pure cultures of a strain of M bovis currently circulating in Michigan livestock and wildlife.
PROCEDURES In the summer and again in the winter, inoculated blocks were placed in secured outdoor facilities where equal numbers of each block type (2/type/season) were exposed to shade or sunlight. Samples were collected from randomly selected areas on the surface of each block beginning within 1 hour after placement (day 0) twice a day for the first 4 days and once a day from days 7 through 11. Bacterial culture of samples was performed to detect viable M bovis.
RESULTS Depending on the exposure conditions, salt blocks yielded viable M bovis for up to 2 days after inoculation and salt-mineral blocks yielded viable M bovis for > 3 days. Survival time was greatest on salt-mineral blocks kept outdoors in the shade during the winter. The odds of recovering viable M bovis from salt-mineral block samples were 4.9 times as great during the winter (vs the summer) and 3.0 times as great with exposure to shade (vs sunlight).
CONCLUSIONS AND CLINICAL RELEVANCE Results from this study indicated that salt and salt-mineral blocks should be considered potential sources of bovine tuberculosis when designing risk mitigation programs for cattle herds in areas with wildlife reservoirs of M bovis.
Objective—To determine whether an interferon (IFN)-γ response sufficient to categorize cattle as positive for tuberculosis can be detected in blood collected at commencement of exsanguination at slaughter.
Animals—15 Holstein cows.
Procedures—12 cows were experimentally sensitized by SC injection with inactivated Mycobacterium bovis in mineral oil, which induced an immune response that mimicked natural infection with M bovis. Three nonsensitized control cows were injected SC with mineral oil alone. By 5 weeks after injection, only the 12 sensitized cows had positive results for tuberculosis with whole blood IFN-γ assay. At that time, all 15 cows were sent to slaughter and samples of blood were collected from each cow immediately before stunning and at commencement of exsanguination (within 90 seconds after stunning). A whole blood IFN-γ assay was performed on the samples. Conditional probability and paired t tests were used to analyze changes in the categorical test interpretation and qualitative IFN-γ production, respectively.
Results—All 12 sensitized cows had positive results for tuberculosis in samples obtained immediately before stunning, and 9 retained positive results for samples obtained at commencement of exsanguination. There was a significant decrease in the mean background-corrected IFN-γ ELISA optical density values for samples obtained at commencement of exsanguination.
Conclusions and Clinical Relevance—IFN-γ response sufficient to classify cattle as positive for tuberculosis could be detected in blood collected at commencement of exsanguination. These findings support further development and use of the IFN-γ assay on blood samples collected at exsanguination as part of a bovine tuberculosis surveillance program.
Objective—To estimate herd-level sensitivity (HSe),
specificity (HSp), and predictive values for a positive
(HPVP) and negative (HPVN) test result for several
testing scenarios for detection of tuberculosis in cattle
by use of simulation modeling.
Sample Population—Empirical distributions of all
herds (15,468) and herds in a 10-county area (1,016) in
Procedures—5 test scenarios were simulated: scenario
1, serial interpretation of the caudal fold tuberculin
(CFT) test and comparative cervical test (CCT);
scenario 2, serial interpretation of the CFT test and
CCT, microbial culture for mycobacteria, and polymerase
chain reaction assay; scenario 3, same as scenario
2 but specificity was fixed at 1.0; and scenario 4,
sensitivity was 0.9 (scenario 4a) or 0.95 (scenario 4b),
and specificity was fixed at 1.0.
Results—Estimates for HSe were reasonably high,
ranging between 0.712 and 0.840. Estimates for HSp
were low when specificity was not fixed at 1.0.
Estimates of HPVP were low for scenarios 1 and 2
(0.042 and 0.143, respectively) but increased to 1.0
when specificity was fixed at 1.0. The HPVN remained
high for all 5 scenarios, ranging between 0.995 and
0.997. As herd size increased, HSe increased and HSp
and HPVP decreased. However, fixing specificity at
1.0 had only minor effects on HSp and HPVN, but HSe
was low when the herd size was small.
Conclusions and Clinical Relevance—Tests used
for detecting cattle herds infected with tuberculosis
work well on a herd basis. Herds with < approximately
100 cattle should be tested more frequently or for
a longer duration than larger herds to ensure that
these small herds are free of tuberculosis. (Am J Vet
Objective—To determine the likelihood of false-positive
results when testing milk samples from individual
cows by use of 3 commercially available assays
(Penzyme Milk Test and the SNAP β-lactamand Delvo-
SP assays) labeled for use with commingled milk.
Sample Population—Milk samples from 111 cows
with mild clinical mastitis.
Procedure—Cows were randomly assigned to the
control (no antimicrobials) or intramammary treatment
group. Posttreatment milk samples were collected
at the first milking after the labeled withholding
period or an equivalent time for controls, randomly
ordered, and tested twice by use of each assay and
once by use of high-performance liquid chromatography.
Sensitivity, specificity, and positive and negative
predictive values were determined for each assay.
Concordance of results for the same sample was
assessed for each assay by calculating κ.
Results—Sensitivities of the Delvo-SP and SNAP β-lactam assays were > 90%, whereas the sensitivity
of the Penzyme Milk Test was 60%. Positive predictive
values (range, 39.29 to 73.68%) were poor for all
3 assays. Concordance of test results was excellent
for the SNAP β-lactam and Delvo-SP assays (κ =
0.846 and 0.813, respectively) but was less for the
Penzyme Milk Test (κ = 0.545).
Conclusions and Clinical Relevance—Because of
the low positive predictive values, these 3 assays may
not be useful for detecting violative antimicrobial
residues in individual milk samples from cows treated
for mild clinical mastitis. However, repeatability of
each assay was considered good to excellent. (Am J
Vet Res 2001;62:1716–1720)