Objective—To evaluate serum haptoglobin concentration at feedlot arrival and subsequent performance and morbidity and mortality rates of calves that developed bovine respiratory disease.
Animals—360 heifer calves and 416 steer and bull calves.
Procedures—Serum samples were obtained from cattle at the time of arrival to a feedlot (day −1) and analyzed for haptoglobin concentration. In experiment 1, calves were classified into groups with a low (< 1.0 μg/mL), medium (1.0 to 3.0 μg/mL), or high (> 3.0 μg/mL) serum haptoglobin concentration and allotted into pens on the basis of group. In experiment 2, calves were classified as having or not having detectable serum haptoglobin concentrations.
Results—In experiment 1, average daily gain from days 1 to 7 decreased as haptoglobin concentration increased. Dry-matter intake (DMI) from days 1 to 21 decreased with increasing haptoglobin concentration, and DMI typically decreased from days 1 to 63. Total bovine respiratory disease morbidity rate typically increased with increasing haptoglobin concentration. At harvest, no differences in carcass characteristics were observed on the basis of haptoglobin concentration. In experiment 2, cattle with measureable serum haptoglobin concentrations at arrival weighed less throughout the experiment, gained less from days 1 to 7, and had lower DMI from days 1 to 42. Overall morbidity rate was not different between groups, but cattle with detectable serum haptoglobin concentrations had higher odds of being treated 3 times.
Conclusions and Clinical Relevance—Serum haptoglobin concentration in cattle at the time of feedlot arrival was not associated with overall performance but may have limited merit for making decisions regarding targeted prophylactic treatment.
Objective—To evaluate enterotoxin production, enterotoxin gene distribution, and genetic diversity of Staphylococcus aureus in milk obtained from cows with subclinical mastitis.
Sample—Milk samples obtained from 350 cows (1,354 mammary glands) on 11 Wisconsin dairy farms.
Procedures—Of 252 S aureus isolates obtained from 146 cows, 83 isolates (from 66 cows with subclinical mastitis) were compared genotypically by use of pulsed-field gel electrophoresis and via PCR identification of toxic shock syndrome toxin 1 (TSST-1) and classical S aureus enterotoxin genes (sea, seb, sec, sed, and see).
Results—Among the 83 S aureus isolates, ≥ 1 enterotoxin genes were identified in 8 (9.6%). Enterotoxin gene distribution was as follows: TSST-1, 7 isolates (8.4%); sec, 5 isolates (6.0%); and sed, 2 isolates (2.4%). Enterotoxin genes sea, seb, and see were not identified. Twelve pulsotypes and 5 subtypes were identified among the 83 isolates; 5 of the 12 pulsotypes were represented by only 1 isolate. In cows of 1 herd, only a single S aureus pulsotype was detected; in cows on most other farms, a variety of pulsotypes were identified. One pulsotype was recovered from 4 farms (n = 23 cows) and another from 5 other farms (16). Isolates with an enterotoxin gene were represented by 6 pulsotypes.
Conclusions and Clinical Relevance—S aureus classical enterotoxins and TSST-1 were rarely recovered from milk samples obtained from cows with subclinical mastitis in Wisconsin. Diverse pulsotypes of S aureus were detected within and among farms, indicating that different strains of S aureus cause subclinical mastitis in dairy cows.
Objective—To evaluate the in vitro susceptibility of various field isolates of Mycobacterium avium subsp paratuberculosis (MAP) to gallium nitrate.
Sample—10 isolates of MAP, including 4 isolated from cattle, 2 isolated from bison, 1 isolated from an alpaca, and 3 isolated from humans.
Procedures—The in vitro susceptibility to gallium nitrate was tested by use of broth culture with detection of MAP growth by means of a nonradiometric automated detection method. For each MAP isolate, a series of 7 dilutions of gallium nitrate (concentrations ranging from 200 to 1,000μM) were tested. Gallium nitrate was considered to have caused 90% and 99% inhibition of the MAP growth when the time to detection for culture of the MAP stock solution and a specific concentration of gallium nitrate was delayed and was similar to that obtained for culture of the MAP stock solution (without the addition of gallium nitrate) diluted 1:10 and 1:100, respectively.
Results—Gallium nitrate inhibited MAP growth in all 10 isolates. The susceptibility to gallium nitrate was variable among isolates, and all isolates of MAP were inhibited in a dose-dependent manner. Overall, the concentration that resulted in 90% inhibition ranged from < 200μM for the most susceptible isolates to 743μM for the least susceptible isolates.
Conclusions and Clinical Relevance—Gallium nitrate had activity against all 10 isolates of MAP tested in vitro and could potentially be used as a prophylactic agent to aid in the control of MAP infections during the neonatal period.
Objective—To evaluate the safety and efficacy of an experimental adjuvanted DNA-plasmid vaccine against West Nile virus (WNV) in red-tailed hawks (Buteo jamaicensis).
Animals—19 permanently disabled but otherwise healthy red-tailed hawks of mixed ages and both sexes without detectable serum antibodies against WNV.
Procedures—Hawks were injected IM with an experimental WNV DNA-plasmid vaccine in an aluminum-phosphate adjuvant (n = 14) or with the adjuvant only (control group; 5). All birds received 2 injections at a 3-week interval. Blood samples for serologic evaluation were collected before the first injection and 4 weeks after the second injection (day 0). At day 0, hawks were injected SC with live WNV. Pre- and postchallenge blood samples were collected at intervals for 14 days for assessment of viremia and antibody determination; oropharyngeal and cloacal swabs were collected for assessment of viral shedding.
Results—Vaccination was not associated with morbidity or deaths. Three of the vaccinated birds seroconverted after the second vaccine injection; all other birds seroconverted following the live virus injection. Vaccinated birds had significantly less severe viremia and shorter and less-intense shedding periods, compared with the control birds.
Conclusions and Clinical Relevance—Use of the WNV DNA-plasmid vaccine in red-tailed hawks was safe, and vaccination attenuated but did not eliminate both the viremia and the intensity of postchallenge shedding following live virus exposure. Further research is warranted to conclusively determine the efficacy of this vaccine preparation for protection of red-tailed hawks and other avian species against WNV-induced disease.
Objective—To determine the chemoprophylactic effect of gallium maltolate on the cumulative incidence of pneumonia caused by Rhodococcus equi infection in foals.
Animals—483 foals born and raised on 12 equine breeding farms with a history of endemic R equi infections.
Procedures—Group 1 foals were treated with a placebo and group 2 foals were treated with gallium maltolate (approx 30 mg/kg, PO, q 24 h) during the first 2 weeks after birth. Foals were monitored for development of pneumonia attributable to R equi infection and for adverse effects of gallium maltolate.
Results—There were no significant differences in the cumulative incidence of R equi pneumonia among the 2 groups.
Conclusions and Clinical Relevance—Chemoprophylaxis via gallium maltolate administered orally at approximately 30 mg/kg daily for the first 2 weeks after birth failed to reduce the cumulative incidence of pneumonia attributable to R equi infection among foals on breeding farms with endemic R equi infections. Further investigation is needed to identify strategies for control of R equi infections.
Objective—To compare efficacy of 2 commercial ovine Campylobacter vaccines and an experimental bacterin in guinea pigs following IP inoculation with Campylobacter jejuni IA3902.
Animals—51 female guinea pigs.
Procedures—Pregnant and nonpregnant animals were randomly assigned to 1 of 4 treatment groups and administered a commercial Campylobacter vaccine labeled for prevention of campylobacteriosis in sheep via two 5-mL doses 14 days apart (vaccine A; n = 13), another labeled for prevention of campylobacteriosis via two 2-mL doses (vaccine B; 12), an experimental bacterin prepared from the challenge strain (12), or a sham vaccine (14). Ten days later, animals were challenged IP with C jejuni IA3902; 48 hours later, animals were euthanized, complete necropsy was performed, and blood and tissue samples were obtained for bacteriologic culture.
Results—Administration of vaccine B or the experimental bacterin, but not vaccine A, significantly reduced 48-hour infection rates versus administration of the sham vaccine. A significantly reduced 48-hour infection rate was associated with administration of vaccine B independent of pregnancy status.
Conclusions and Clinical Relevance—Administration of vaccine B significantly reduced infection in guinea pigs challenged with C jejuni IA3902, similar to a homologous bacterin. Results suggested that vaccine B or an autogenous product may be effective in controlling ovine campylobacteriosis caused by this emergent abortifacient strain. Bacteriologic culture of blood, liver, bile, and uterus in nonpregnant guinea pigs 48 hours after inoculation may be a useful screening tool for comparing efficacy of C jejuni vaccines.
Objective—To investigate shedding of chlamydiae from conjunctiva and genital tracts of cats without clinical signs of conjunctivitis or other infectious disease in relation to their titers of serum antibodies against chlamydiae and to serum amyloid A (SAA) and serum α1-acid glycoprotein (AGP) concentrations.
Animals—62 healthy cats.
Procedures—Serum from each cat was analyzed for antibodies against chlamydiae and for SAA and AGP concentrations. Swab samples from the conjunctival sac and genital tract were analyzed with a real-time PCR assay for Chlamydiaceae.
Results—4 of 8 of cats with high antibody titers (ie, 1,600) shed chlamydiae, but only from the conjunctiva. Chlamydiae could not be detected in samples from cats with lower antibody titers nor from any genital tract samples. In cats with antibody titers of 1,600, mean ± SD SAA concentration was significantly higher when chlamydiae were detected in conjunctival swab samples (3.9 ± 1.0 mg/L) than when no chlamydiae were detected (1.4 ± 1.0 mg/L). However, SAA concentration was greater than the limit for an acute-phase response in only one of those cats. There was no significant difference in serum AGP concentrations between cats with high titers that were or were not shedding chlamydiae. Nine of 30 (30%) cats (5 with and 4 without detectable serum antibodies against chlamydiae) that had been mated developed reproductive disorders.
Conclusions and Clinical Relevance—Clinically normal cats with high chlamydiae-specific antibody titers can shed and thus transmit chlamydiae. Venereal spread from cats without clinical signs of infection is likely not common.
Objective—To determine efficacy of a modified-live virus (MLV) vaccine containing bovine viral diarrhea virus (BVDV) 1a and 2a against fetal infection in heifers exposed to cattle persistently infected (PI) with BVDV subtype 1 b.
Animals—50 heifers and their fetuses.
Procedures—Susceptible heifers received a placebo vaccine administered IM or a vaccine containing MLV strains of BVDV1a and BVDV2a administered IM or SC. On day 124 (64 to 89 days of gestation), 50 pregnant heifers (20 vaccinated SC, 20 vaccinated IM, and 10 control heifers) were challenge exposed to 8 PI cattle. On days 207 to 209, fetuses were recovered from heifers and used for testing.
Results—2 control heifers aborted following challenge exposure; both fetuses were unavailable for testing. Eleven fetuses (8 control heifers and 1 IM and 2 SC vaccinates) were positive for BVDV via virus isolation (VI) and for BVDV antigen via immunohistochemical analysis in multiple tissues. Two additional fetuses from IM vaccinates were considered exposed to BVDV (one was seropositive for BVDV and the second was positive via VI in fetal tissues). A third fetus in the SC vaccinates was positive for BVDV via VI from serum alone. Vaccination against BVDV provided fetal protection in IM vaccinated (17/20) and SC vaccinated (17/20) heifers, but all control heifers (10/10) were considered infected.
Conclusions and Clinical Relevance—1 dose of a BVDV1a and 2a MLV vaccine administered SC or IM prior to breeding helped protect against fetal infection in pregnant heifers exposed to cattle PI with BVDV1b.
Objective—To investigate adhesion phenotypes of pigs of Chinese and Western breeds and a specific crossbreed with regard to enterotoxigenic Escherichia coli (ETEC) with fimbrial adhesins K99 (F5), 987P (F6), and F41 (F7).
Animals—Purebred 6- to 8-week-old pigs of 3 Western breeds introduced into China (n = 144) and 12 Chinese breeds (148) and 1,330 adult White Duroc-Erhualian crossbred pigs.
Procedures—Brush border preparations were prepared from jejunal specimens collected from each pig following euthanasia. Each preparation was incubated with ETEC strains that had fimbrial adhesins K99, 987R or F41; an ETEC K88− strain was used as a negative control sample. The mean number of brush border-bound bacteria in aliquots of the bacteria-brush border suspensions (determined via phase-contrast microscopy) was used to determine each pig's adhesion phenotype for ETEC K99, 987R and F41 strains; the phenotype was classified as adhesive (susceptible) if ≥ 10% of examined brush borders bound > 2 bacteria.
Results—Most purebred and crossbred pigs had nonadhesive phenotypes with regard to ETEC K99 and 987P strains. For the F41 strain, 34.9% and 65.1% of all purebred pigs had adhesive and nonadhesive phenotypes, respectively; among crossbred pigs, these values were 39.2% and 60.8%, respectively. The percentage of pigs with the F41 adhesive phenotype was higher among Western breeds than it was among Chinese breeds (38.9% vs 31.1%).
Conclusions and Clinical Relevance—Results suggested that the ETEC F41 strain, but not the K99 or 987P strain, might be a cause of diarrhea in 6- to 8-week-old pigs in China.
Objective—To determine whether airborne concentrations of virulent Rhodococcus equi at 2 horse breeding farms varied on the basis of location, time of day, and month.
Sample Population—2 farms in central Kentucky with recurrent R equi-induced pneumonia in foals.
Procedures—From February through July 2008, air samples were collected hourly for a 24-hour period each month from stalls and paddocks used to house mares and their foals. Concentrations of airborne virulent R equi were determined via a modified colony immunoblot technique. Differences were compared by use of zero-inflated negative binomial methods to determine effects of location, time, and month.
Results—Whether mares and foals were housed predominantly in stalls or paddocks significantly affected results for location of sample collection (stall vs paddock) by increasing airborne concentrations of virulent R equi at the site where horses were predominantly housed. Airborne concentrations of virulent R equi were significantly higher from 6:00 pm through 11:59 pm than for the period from midnight through 5:59 am. Airborne concentrations of virulent R equi did not differ significantly between farms or among months.
Conclusions and Clinical Relevance—Airborne concentrations of virulent R equi were significantly increased when horses were predominantly housed at the site for collection of air samples (ie, higher in stalls when horses were predominantly housed in stalls and higher in paddocks when horses were predominantly housed in paddocks). Concentrations of virulent R equi among air samples collected between the hours of 6:00 am and midnight appeared similar.