Objective—To examine effects of co-infection with
porcine reproductive and respiratory syndrome virus
(PRRSV) and Bordetella bronchiseptica in pigs.
Animals—Forty 3-week-old pigs.
Procedure—30 pigs (10 pigs/group) were inoculated
with PRRSV, B bronchiseptica, or both. Ten noninoculated
pigs were control animals.
Results—Clinical signs, febrile response, and
decreased weight gain were most severe in the group
inoculated with both organisms. The PRRSV was isolated
from all pigs in both groups inoculated with
virus. All pigs in both groups that received PRRSV had
gross and microscopic lesions consistent with interstitial
pneumonia. Bordetella bronchiseptica was cultured
from all pigs in both groups inoculated with that
bacterium. Colonization of anatomic sites by B bronchiseptica
was comparable between both groups.
Pigs in the group that received only B bronchiseptica
lacked gross or microscopic lung lesions, and B bronchiseptica
was not isolated from lung tissue. In the
group inoculated with B bronchiseptica and PRRSV, 3
of 5 pigs 10 days after inoculation and 5 of 5 pigs 21
days after inoculation had gross and microscopic
lesions consistent with bacterial bronchopneumonia,
and B bronchiseptica was isolated from the lungs of 7
of those 10 pigs.
Conclusions and Clinical Relevance—Clinical disease
was exacerbated in co-infected pigs, including
an increased febrile response, decreased weight gain,
and B bronchiseptica-induced pneumonia. Bordetella
bronchiseptica and PRRSV may circulate in a herd and
cause subclinical infections. Therefore, co-infection
with these organisms may cause clinical respiratory
tract disease and leave pigs more susceptible to subsequent
infection with opportunistic bacteria. (Am J Vet Res 2000;61:892–899)
Objective—To determine effects of intranasal inoculation
with porcine reproductive and respiratory syndrome
virus (PRRSV) or Bordetella bronchiseptica on
challenge with nontoxigenic Pasteurella multocida in
Animals—Seventy 3-week-old pigs.
Procedure—In experiment 1, pigs were not inoculated
(n= 10) or were inoculated with PRRSV (10), P multocida
(10), or PRRSV followed by challenge with P
multocida (10). In experiment 2, pigs were not inoculated
(n = 10) or were inoculated with B bronchiseptica
(10) or PRRSV and B bronchiseptica (10); all pigs
were challenged with P multocida. Five pigs from
each group were necropsied 14 and 21 days after initial
Results—Pasteurella multocida was not isolated
from tissue specimens of pigs challenged with P multocida
alone or after inoculation with PRRSV.
However, in pigs challenged after inoculation with B
bronchiseptica, P multocida was isolated from specimens
of the nasal cavity and tonsil of the soft palate.
Number of bacteria isolated increased in pigs challenged
after coinoculation with PRRSV and B bronchiseptica,
and all 3 agents were isolated from pneumonic
lesions in these pigs.
Conclusion and Clinical Relevance—Infection of
pigs with B bronchiseptica but not PRRSV prior to
challenge with P multocida resulted in colonization of
the upper respiratory tract and tonsil of the soft palate
with P multocida. Coinfection with PRRSV and B
bronchiseptica predisposed pigs to infection of the
upper respiratory tract and lung with P multocida.
Porcine reproductive and respiratory syndrome virus
and B bronchiseptica may interact to adversely affect
respiratory tract defense mechanisms, leaving pigs
especially vulnerable to infection with secondary
agents such as P multocida. (Am J Vet Res 2001;
Objective—To determine whether vaccine virus can be detected by use of reverse transcriptase (RT)-PCR assays for pooled and individual skin samples obtained from cattle after vaccination with a commercially available modified-live bovine viral diarrhea virus (BVDV) vaccine.
Animals—12 BVDV-seropositive steer calves and 7 BVDV-seronegative (antibody titer < 1:4) heifers; all cattle were free of persistent infection with BVDV.
Procedures—2 experiments were conducted. Cattle were vaccinated on day 0 with a commercially available modified-live BVDV vaccine. Skin samples were collected on days 0, 3 to 14, 16, and 18 for virus detection by use of RT-PCR assay on individual and pooled samples. In addition, blood samples and nasal swab specimens were collected for virus isolation.
Results—All cattle, regardless of serologic status, had negative results for BVDV as determined by use of RT-PCR assay of individual and pooled skin samples. Virus was detected via virus isolation in serum or the buffy coat in 5 of 7 heifers that were seronegative when vaccinated.
Conclusions and Clinical Relevance—These findings indicated that it would be unlikely to detect BVDV vaccine virus in skin by use of RT-PCR assay of individual or pooled skin samples obtained from cattle after vaccination with a commercially available modified-live BVDV vaccine. Veterinarians and producers should be confident that positive test results for BVDV on skin samples would not likely be caused by the vaccination virus after administration of a modified-live virus vaccine.
Objective—To determine whether cattle testing positive
for Mycobacterium avium subsp paratuberculosisas
determined by microbial culture of feces or antibody
ELISA were more likely to have false-positive
responses on the caudal fold tuberculin (CFT) test or
interferon-γ (IFN-γ) assay for Mycobacterium bovis
than cattle testing negative for M paratuberculosis.
Animals—1,043 cattle from 10 herds in Michigan.
Procedure—Feces and blood samples for plasma
were collected from cattle ≥ 24 months old on the day
the CFT test was read. Fecal samples were submitted
for microbial culture for M paratuberculosis. Plasma
samples were tested for antibody against M paratuberculosis,
and IFN-γ after stimulation with purified
protein derivative tuberculin from M bovis or M avium.
Results—Of 1,043 cattle, 180 (17.3%) had positive CFT
test results (suspects) and 8 (0.8%) had positive IFN-γ
assay results after stimulation with purified protein
derivative tuberculin from M bovis. Forty-five (4.3%) and
115 (11.0%) cattle tested positive for M paratuberculosis
as determined by microbial culture of feces and antibody
ELISA, respectively. Cattle with positive responses
for M paratuberculosis appeared to have an
increased likelihood of false-positive results on the CFT
test, although this association was not significant.
Conclusions and Clinical Relevance—No significant
association was detected among cattle testing positive
for M paratuberculosis as determined by microbial
culture of feces and antibody ELISA and positive
CFT test and IFN-γ assay results for M bovis. (J Am
Vet Med Assoc 2005;226:429–435)
Objective—To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV.
Animals—60 crossbred beef heifers and 4 cows persistently infected with BVDV.
Procedures—Beef heifers were allocated to 2 groups. One group was vaccinated twice (21-day interval between the initial and booster vaccinations) with a commercially available vaccine against BVDV, and the other group served as nonvaccinated control cattle. Estrus was induced, and the heifers were bred. Pregnancy was confirmed by transrectal palpation. Four cows persistently infected with BVDV were housed with 30 pregnant heifers (15 each from the vaccinated and nonvaccinated groups) from day 52 to 150 of gestation. Fetuses were then harvested by cesarean section and tested for evidence of BVDV infection.
Results—1 control heifer aborted after introduction of the persistently infected cows. Bovine viral diarrhea virus was isolated from 14 of 14 fetuses obtained via cesarean section from control heifers but from only 4 of 15 fetuses obtained via cesarean section from vaccinated heifers; these proportions differed significantly.
Conclusions and Clinical Relevance—A commercially available multivalent vaccine containing an inactivated BVDV fraction significantly reduced the risk of fetal infection with BVDV in heifers continually exposed to cattle persistently infected with BVDV. However, not all vaccinated cattle were protected, which emphasizes the need for biosecurity measures and elimination of cattle persistently infected with BVDV in addition to vaccination within a herd.
Objective—To collect and partially characterize strains of bovine viral diarrhea viruses(BVDVs) isolated from persistently infected (PI) calves born to vaccinated dams, determine genetic diversity of the isolated viruses, and identify regional distribution of genetically similar virus subpopulations.
Sample Population—17 noncytopathic (NCP) BVDVs from PI calves from 11 herds of beef or dairy cattle.
Procedures—Viral RNA was extracted from infected cell cultures, and BVDV-specific PCR primers were used to amplify > 1,000 bases of the viral genome. Derived sequences were used for molecular phylogenetic analyses to determine the viral genotype and viral genogroup and to assess genetic similarity among BVDVs.
Results—Analysis of the 17 NCP strains of BVDV failed to detect a viral genotype or viral genogroup not already reported to exist in the United States. One virus was classified as genotype 1, genogroup 1b, and 16 viruses were classified as genotype 2, genogroup 2a. Genotype 2 strains were genetically diverse, and genetic similarities were not obvious among viruses from geographic regions larger than a small locale.
Conclusions and Clinical Relevance—Viruses isolated from herds where a genotype 1, genogroup 1a BVDV vaccine was administered prior to breeding were primarily genetically diverse genotype 2, genogroup 2a BVDVs. Vaccination with multiple BVDV genotypes may be needed to improve protection. Methods used in this study to obtain and analyze field strains are applicable to assessing efficacy of current BVDV vaccines. Candidates for future vaccines are viruses that appear able to elude the immune response of cattle vaccinated against BVDV with existing vaccines.
Case Description—3 unrelated, densely populated, dynamic ferret populations with severe outbreaks of enteric coccidiosis were evaluated.
Clinical Findings—In each outbreak, morbidity rate was high, there were an appreciable number of deaths, and ferrets of all ages were affected. Affected individuals had acute onset of diarrhea, and feces often contained frank or digested blood. Other clinical signs included dehydration, weakness, lethargy, and weight loss. Fecal examinations of affected ferrets revealed sporadic and inconsistent shedding of coccidial oocysts. Necropsy findings included moderate to marked atrophic enteritis associated with numerous intraepithelial and fewer extracellular coccidial life stages. Sporulated oocysts isolated from feces were consistent with Eimeria furonis. A PCR assay was performed on formalin-fixed, paraffin-embedded sections of intestine for the gene encoding the small subunit of rRNA yielded products with sequences identical to those described for E furonis.
Treatment and Outcome—Supportive care and treatment with sulfadimethoxine over the course of these outbreaks was palliative, but long-term treatment was required and failed to completely eradicate infection as identified by the subsequent finding of oocysts in fecal samples.
Clinical Relevance—Enteric coccidiosis due to infection with E furonis has typically been reported to be subclinical rather than to cause severe gastrointestinal disease in ferrets. This report indicated that infection with E furonis may have contributed to severe enteric disease with high morbidity and mortality rates in 3 densely populated, dynamic groups of ferrets. Furthermore, long-term treatment with anti-coccidials may be required in outbreak situations, but may be ineffectual in completely eradicating infection.
Objective—To evaluate the effects of a voluntary regional bovine viral diarrhea virus (BVDV) control project implemented in the Upper Peninsula of Michigan.
Sample—294 cattle producers and 11,917 cattle from the Upper Peninsula.
Procedures—Producer participation was assessed to determine the effectiveness of the project's promotional and educational campaigns. Participating herds were screened for cattle persistently infected (PI) with BVDV by real-time reverse transcriptase PCR assay on ear notch specimens from all newborn calves and cattle that did not calve (bulls and young stock) during the year of enrollment. Responses to a survey administered to producers 4 years after project initiation were evaluated to assess the project's effect on BVDV management practices implemented by producers.
Results—294 of 495 (59%) known cattle producers in the Upper Peninsula participated in the project, and 11,917 cattle from 232 herds were tested for BVDV, of which 22 (0.18%) cattle from 9 (3.9%) herds were identified as PI with BVDV and euthanized or slaughtered. Of 140 survey respondents, 85 (61%) indicated they would test all new herd additions for BVDV, 83 (59%) would quarantine new herd additions for 30 days before introducing them to the main herd, and 81 (58%) would use the fact that their herd was free of cattle PI with BVDV for marketing purposes.
Conclusions and Clinical Relevance—Results indicated that the project enhanced producer knowledge about BVDV and led to changes in producer behavior regarding BVDV management. Stakeholder engagement was as critical to project success as was increased BVDV knowledge.
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.