Objectives—To determine whether vaccination with
a killed vaccine prevents fecal shedding of Mycobacterium
avium subsp paratuberculosis, to compare
effectiveness of a culture and cull program in vaccinated
and nonvaccinated herds, and to compare
paratuberculosis-related preventive management in
vaccinated and nonvaccinated herds.
Design—Cross-sectional study (study A) in vaccinated
(n = 25) and nonvaccinated (29) herds of dairy
cows. Longitudinal study (study B) in vaccinated
(n = 2) and nonvaccinated (2) herds of dairy cows.
Procedure—In study A, fecal samples were obtained
from adult cows in herds with and without a history
of vaccination with a killed vaccine. Management
measures were evaluated. In study B, fecal samples
were obtained 4 times at 6-month intervals from
cows older than 6 months. Cows that had positive
test results were removed from the herd directly after
the outcome of the culture.
Results—In study A, differences were not detected
among the 25 herds that were vaccinated; culture
results were positive for M avium subsp paratuberculosis
in 4.4% of herds. In 29 herds that had not been
vaccinated, culture results were positive in 6.7%. In
study B, the percentage of positive results on culture
decreased from 10.9% and 5.7% to 3.5% and 0%,
respectively in the 2 vaccinated herds. In the 2 nonvaccinated
herds, percentages decreased from 6.1%
and 16.5% to 0% and 2.3%, respectively.
Management practices were different between herds
that were vaccinated and herds that were not; owners
of herds that were not vaccinated followed more
preventive management procedures and practiced
less feeding of raw milk to calves.
Conclusions and Clinical Relevance—Vaccination
of calves with a killed vaccine does not prevent transmission
of M avium subsp paratuberculosis; therefore,
hygienic practices remain essential in herd management.
(Am J Vet Res 2001;62:270–274)
Objective—To compare serum total protein (sTP) and serum IgG (sIgG) concentrations In neonatal calves administered colostrum or a bovine serum-based colostrum replacement (CR) product followed by a bovine serum-based colostrum supplement (CS) product.
Design—Randomized controlled clinical trial.
Animals—18 Jersey and 269 Holstein neonatal heifer calves.
Procedures—141 calves were given 4 L of colostrum in 1 or 2 feedings (first or only feeding was provided ≤ 2 hours after birth; when applicable, a second feeding was provided between 2 and 12 hours after birth). Other calves (n = 146) were fed 2 L of a CR product ≤ 2 hours after birth and then 2 L of a CS product between 2 and 12 hours after birth. Concentrations of sTP and sIgG were measured 1 to 7 days after birth. Data from cohorts on individual farms and for all farms were analyzed.
Results—Mean sTP and sIgG concentrations differed significantly between feeding groups. In calves fed colostrum and calves fed CR and CS products, mean ± SD sTP concentration was 5.58 ± 0.67 g/dL and 5.26 ± 0.54 g/dL, respectively, and mean sIgG concentration was 1,868 ± 854 mg/dL and 1,320 ± 620 mg/dL, respectively. The percentage of calves that had failure of passive transfer of immunity (ie, sIgG concentrations < 1,000 mg/dL) was not significantly different between groups.
Conclusions and Clinical Relevance—Results suggested that sequential feeding of bovine serum-based CR and CS products to neonatal calves is an alternative to feeding colostrum for achieving passive transfer of immunity.
Objective—To evaluate the seroprevalence of paratuberculosis by use of 2 commercial ELISAs in association with prevalence of fecal shedding of mycobacteria within beef cattle herds.
Design—Cross-sectional field study.
Animals—Six beef herds (affected herds; 522 cattle) with and 3 geographically matched herds (181 cattle) without high seroprevalence of paratuberculosis.
Procedures—Blood and fecal samples were collected from adult cattle and assessed for serum anti–Mycobacterium avium subsp paratuberculosis (MAP) antibodies with 2 commercial ELISA kits and submitted for bacterial culture for MAP and environmental bacteria (termed environmental mycobacteria) via a radiometric method, respectively. Species of mycobacterial isolates were identified, and sensitivities and specificities of the 2 ELISAs were compared.
Results—Compared with comparison cattle, cattle from affected herds were 9.4 times as likely to have environmental mycobacteria isolated from feces. Among the 6 affected and 3 comparison herds, the proportions of cattle shedding environmental mycobacteria were 0.225 (range, 0.1 to 0.72) and 0.04 (range, 0 to 0.06), respectively. Although relative MAP-detection specificities (compared with bacterial culture of feces) were different between the 2 ELISAs, sensitivities were not. Nine environmental mycobacterial species were iden-tified from participating herds. All affected herds apparently had ≥ 1 bovid infected with MAP, although MAP was not isolated from any cattle in comparison herds.
Conclusions and Clinical Relevance—In beef herds with persistently high rates of false-positive ELISA results, which may be associated with recovery of environmental myco-bacteria from feces, organism detection via bacterial culture of feces or PCR assay should direct paratuberculosis control measures.
Objective—To determine efficacy and safety of a
commercial modified-live canine distemper virus
(CDV) vaccine used for prophylaxis in domestic ferrets.
Animals—Sixteen 16-week-old neutered male ferrets.
Procedures— Equal groups of ferrets were inoculated
subcutaneously at 16 and 20 weeks of age with
saline (0.9% NaCl) solution or a vaccine derived from
the Onderstepoort CDV strain and attenuated in a primate
cell line. Live virulent CDV was administered to
all ferrets intranasally and orally 3 weeks after the second
inoculation. Clinical signs and body weights were
monitored regularly during the study. Blood samples
for serologic examination were drawn prior to each
inoculation, before challenge exposure, and 10, 15,
and 21 days after exposure. Blood samples for
reverse transcriptase polymerase chain reaction (RT-PCR)
were obtained 5 days after the first vaccination,
and 5, 10, 15, and 21 days after challenge exposure.
Results—After challenge exposure, control ferrets
had significantly more clinical signs and weight loss,
compared with vaccinates. All vaccinated ferrets survived,
whereas all control ferrets died. The RT-PCR
assay was successful in detecting CDV in blood and
fresh or formalin-fixed tissues from infected ferrets.
Conclusions and Clinical Relevance—Findings suggest
that the vaccine when given SC to domestic ferrets
as directed is safe and protective against challenge
exposure with virulent CDV. The RT-PCR assay
may simplify detection of CDV in fresh and fixed tissues.
(Am J Vet Res 2001;62:736–740)
Objective—To evaluate the effect of exposure to environmental mycobacteria on results of 2 commercial ELISAs for paratuberculosis in cattle.
Animals—19 weaned crossbred beef calves.
Procedures—Calves were inoculated SC with 1 of 5 mycobacterial isolates (3 calves/isolate) derived from herds with high proportions of false-positive serologic reactions for paratuberculosis, Mycobacterium avium subsp paratuberculosis (MAP; positive control inoculum; 2 calves), or mineral oil (negative control inoculum; 2 calves). Sera were assessed at intervals by use of 2 ELISAs (A and B) for paratuberculosis in cattle, and all calves underwent tuberculosis testing at the end of the study.
Results—Neither mineral oil–inoculated calf had positive results with either ELISA during the study. Both MAP-inoculated calves were identified as seropositive via ELISA-A, and 1 calf was identified as seropositive via ELISA-B. By use of ELISA-A, ≥ 1 false-positive reaction over time was detected in 2, 3, 3, and 1 of the 3 calves injected with Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium scrofulaceum, or Mycobacterium terrae, respectively. By use of ELISA-B, only M scrofulaceum induced false-positive reactions (2/3 calves). Calves that had at least 1 positive ELISA-A result were more likely to be classified as suspect reactors via the caudal fold tuberculosis test.
Conclusions and Clinical Relevance—False-positive serologic reactions may occur during use of commercially available ELISAs for paratuberculosis in calves experimentally exposed to environmental mycobacteria; naturally occurring exposures with these mycobacteria may represent a cause for high proportions of false-positive serologic reactions for paratu-berculosis in some cattle herds.
The report provided here contains a simplified set of diagnostic testing recommendations. These recommendations were developed on the basis of research funded by the USDA–Animal and Plant Health Inspection Service–Veterinary Services through a cooperative agreement. The report is intended to provide simple, practical, cost-effective consensus testing recommendations for cattle herds that are not enrolled in the US Test-Negative Program. The information has been reviewed by paratuberculosis (Johne's disease) experts at the USDA and academic centers as well as stakeholders in various segments of the cattle industry. The recommendations were accepted by the National Johne's Working Group and Johne's Disease Committee of the US Animal Health Association during their annual meetings in October 2006.
The report is intended to aid veterinarians who work with cattle producers in the United States. The recommendations are based on information available up to October 2006. There is a paucity of large-scale, high-quality studies of multiple tests conducted on samples obtained from the same cattle. It is understood that there may be special circumstances that require deviation from these recommendations. Furthermore, as new information becomes available and assays are improved and their accuracy is critically evaluated, changes to these recommendations may be necessary.