Persistent bovine viral diarrhoea virus infection in US beef herds.

In the summer of 1996, we screened 18,931 calves in 128 beef herds located in five US states for persistent bovine viral diarrhea virus (BVDV) infection. Of these, 76 herds were randomly selected from the client database of collaborating veterinary practices, and 52 herds were suspected by the collaborating veterinarians to have BVDV infection based on history or clinical signs. Serum was obtained from each calf in the cooperating herds prior to 4 months of age and tested for the presence of BVDV by microtiter virus isolation. Information about each of the herds (including management practices, vaccination history, and breeding- and calving-season production measures) were collected by the collaborating veterinarians using standardized questionnaires. A total of 56 BVDV-positive calves in 13 herds were identified on initial screening. Ten (19%) of the BVDV-suspect herds and three (4%) of the randomly selected herds had > or = 1 BVDV-positive calf at initial screening. Multiple BVDV-positive calves were identified in 10 of those 13 herds. Follow-up information was obtained for 54 of the 56 positive calves. Ten out of 54 (18%) died prior to weaning, and 1 (2%) was sold because of unusually poor growth. Thirty-three out of 54 (61%) of the initially positive calves remained BVDV positive at 6 months of age - confirming persistent-infection (PI) status. Dams of 45 of the 56 positive calves were tested, with 3 (7%) identified as positive - indicating most PI calves were products of acute dam infection during gestation. The proportion of cows that were pregnant at the fall 1995 pregnancy examination was 5% lower in herds with PI calves born during the 1996 calving season than in randomly selected herds without PI calves. Most of the calves we identified with persistent BVDV infections survived to weaning, and could provide a constant source of virus to the herd throughout the breeding season and early gestation.

Characterization of antigenic proteins from Tritrichomonas foetus recognized by antibodies in rabbit serum, bovine serum and bovine cervicovaginal mucus.

Tritrichomonas foetus is an obligate parasite of the bovine urogenital tract and is recognized as 1 of the more common infectious agents causing decreased reproductive efficiency in beef cattle. Infections result in reproductive failure and produce considerable economic loss. Vaccination of heifers with vaccines containing T. foetus induces elevated serological responses to many T. foetus antigens, decreases the rate and/or length of infection with T. foetus, and decreases fetal loss caused by infection. Because T. foetus infections are usually limited to lumen and mucosal surfaces of the reproductive tract, it has been assumed that protection from infection and abortion is partially mediated by immunoglobulins in the uterus and vagina. The objective of this study was to identify and characterize specific antigens of T. foetus that show promise for use in a recombinant vaccine that will generate a protective mucosal immune response in cattle. Surface proteins were identified by using polyclonal rabbit anti-trichomonal sera eluted from paraformaldehyde-fixed cells. Analyses of these proteins, utilizing mucosal antibodies from vaccinated and convalescent cows, have identified proteins involved in generating a local immune response. Western immunoblot analysis indicates that these proteins are well conserved and are excellent candidates for incorporation into a recombinant vaccine.

Specific antibodies in serum and vaginal mucus of heifers inoculated with a vaccine containing Tritrichomonas foetus.

Thirty-five heifers were allotted to 3 groups. Group 1 (control) consisted of 10 heifers that were not vaccinated and were challenge exposed by breeding to infected bulls. Group 2 (natural challenge exposure) consisted of 10 heifers that were vaccinated and challenge exposed by breeding to infected bulls. Group 3 (experimental challenge exposure) consisted of 15 heifers that were vaccinated and challenge exposed by breeding to infected bulls and by intravaginal inoculation with 10(7) Tritrichomonas foetus. Total immunoglobulin concentrations and specific trichomonal antibodies were determined in serum and vaginal secretions of heifers, using radial immunodiffusion and ELISA procedures. Control heifers remained infected for a mean of 10.6 weeks (range, 0 to 18 weeks), and heifers of the natural and experimental challenge-exposure groups remained infected for 3.2 and 5.0 weeks, respectively (range, 0 to 12 weeks). Total serum and cervicovaginal mucus concentrations of IgM, IgA, IgG1, and IgG2 did not change significantly after vaccination or challenge exposure. However, ELISA titers of total trichomonal antibodies increased up to 1:10,000 (range, 1:400 to 1:10,000) in serum after vaccination, and increased approximately tenfold above background in cervicovaginal mucus. In serum, the predominant trichomonal antibody isotype was IgG1, although trichomonal IgA and IgM antibodies also increased. The predominant trichomonal antibody detected in cervicovaginal mucus was IgA. Antibody titers in serum and cervicovaginal mucus of vaccinated heifers were not increased by infection. However, in control heifers, the total local trichomonal antibody response increased three- to fivefold after infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of the efficacy of inoculating cattle with a vaccine containing Tritrichomonas foetus.

To test the efficacy of a polyvalent Tritrichomonas foetus vaccine, 130 nulliparous heifers were randomly assigned to either receive the test T foetus vaccine or to serve as nonvaccinated controls. The polyvalent test vaccine consisted of a Campylobacter fetus/Leptospira canicola-grippotyphosa-hardjo-icterohaemorrhagiae-pamona bacterine containing 5 x 10(7) killed T foetus/dose. The polyvalent control vaccine consisted of the aforementioned formulation without T foetus. Heifers were administered 2 doses of control or experimental vaccine at 3-week intervals. Heifers were bred to T foetus-infected bulls and their conception and pregnancy rates were determined throughout gestation. In addition, serum samples were analyzed to determine induced concentrations of antitrichomonal antibodies and vaginal secretions were sampled to determine T foetus infection rates in control and vaccinated animals. One week after each of the 15-day breeding periods, 60% (6 of 10) of tested vaccinates and 80% (8 of 10) of tested control animals were T foetus culture-positive. The mean duration of infection of vaccinates was 3.8 weeks (+/- 7.5 days), compared with 5.4 weeks (+/- 7.5 days) of infection for control heifers. All vaccinates developed increased immunofluorescence and serum neutralizing antibody titers following the first immunization, and had additional increases of at least fourfold in response to the second injection. In contrast, no consistent increase in immunofluorescence or serum neutralizing antibodies was observed in control animals. Conception rates were 89.2% for vaccinates and 85.9% for control animals 30 days after breeding and 80 to 90% of these remained pregnant 60 days after breeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations of the incidence of bovine trichomoniasis in nevada and of the efficacy of immunizing cattle with vaccines containing Tritrichomonas foetus.

Trichomonas cultures taken from 2389 bulls showed that approximately 4.7% of them were infected. Correlation of these data with the ranches from which diagnostic samples were obtained indicated that in the period of 1984 through 1987 26.7 to 44.1% of ranches had at least one infected bull. Thirty-four 18-month-old Holstein heifers were assigned to one of three groups, controls n = 12 animals, soluble vaccine n = 11 animals, and whole vaccine n = 11 animals to determine the effect of Tritrichomonas foetus vaccines on the reproductive performance of T . foetus infected animals. Heifers were bred with T . foetus infected bulls beginning two weeks after the second T . foetus vaccination. All immunized animals developed antibody titers of at least 1:1000 following vaccination. In addition, all control and immunized animals became infected with T . foetus . However, the duration of infection was approximately two weeks shorter in immunized animals. Approximately 42% (5 of 12) of control heifers remained infected with T . foetus for the duration of the experiment, while only 18% (2 of 11) of each of the vaccine groups remained infected for the duration of the experiment. Finally, 27% (3 of 11) of heifers in each of the vaccine groups were pregnant at slaughter, while none of the control heifers were pregnant at slaughter. Therefore, both vaccine formulations appeared to protect heifers (P<0.05) from fetal loss due to trichomoniasis.

Synchronization of parturition in beef cattle with prostaglandin and dexamethasone.

The effectiveness of dexamethasone and prostaglandin in combination for induction and synchronization of parturition in cattle was evaluated in 100 pregnant Angus, Hereford, Charolais and Simmental cows. Cows were distributed equally by breed, day of gestation and cow age to one of three treatments: 1) Control, 2) Dexamethasone (25 mg) plus prostaglandin F(2alpha) (25 mg) or 3) Dexamethasone (25 mg) plus fenprostalene (1 mg). Hormones were administered simultaneously from 275 to 283 d of gestation. Gestation length at calving for control cows differed significantly (P < 0.01) among breeds: Angus, 278.5 +/- 0.9; Hereford, 283.1 +/- 1.1; Charolais, 283.2 +/- 1.5; and Simmental, 285.4 +/- 1.2 d. For hormone-treated cows, 80% of the calves were born between 30 and 46 h after the hormone injections; overall mean was 37.6 +/- 1.1 h. Calving response did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) versus fenprostalene (36.5 +/- 1.6 vs 38.6 +/- 1.6 h) or among cow age, day of gestation, or breed. Also, duration of labor, calving difficulty and calf viability did not differ between calves born at an induced or spontaneous parturition. The incidence of placenta retained for >24 h was higher for induced than spontaneous parturition (21.0 vs 0.0%), but it did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) or fenprostalene (19.2 vs 22.6%). An acceptable degree of synchrony of parturition was attained by the administration of prostaglandin F(2alpha) or fenprostalene in combination with dexamethasone. The higher incidence of retained placenta in treated than control cows did not affect subsequent fertility. The longer biological half-life for fenprostalene than for prostaglandin F(2alpha) provided no improvement in increasing synchrony of parturition or decreasing frequency of retained placenta.

The toxicology and composition of bovine tissues after parenteral administration of high levels of copper salts.

Copper toxicity was observed when crossbred cows were injected with 480 mg copper sc. Five head died after copper disodium EDTA (edetate) injections but no losses occurred with copper glycinate. Necropsy, histopathology and plasma enzyme values indicated severe hepatic necrosis in the affected cattle. Plasma copper levels peaked 2 hr postinjection (3.82 micrograms/ml) in cattle that lived after EDTA injections, but about half this level (2.00 micrograms/ml) of copper was observed in the animals that died and 0.65 in the glycinate-treated animals (P less than .01). Ceruloplasmin levels were low in all cattle (2.1 to 7.2 IU/L). Plasma iron increased between 2 (179 micrograms/dl) to 4 (422 micrograms/dl) hr after injection for all cattle and remained high at 8 hr (501 micrograms/dl postinjection; P less than .01). After copper was administered, plasma zinc decreased 45 to 75% of pre-injection levels (P less than .01). Plasma urea nitrogen was not modified by the treatments. Hemolysis was not observed in any of the animals.

Infectious bovine keratoconjunctivitis: evidence for genetic modulation of resistance in purebred Hereford cattle.

A vaccination study was conducted in a herd of purebred Hereford cattle representing 4 selection (genetic) lines. For each of 2 years, half of the cattle were vaccinated with a pilus-enriched Moraxella bovis bacterin. Cows were vaccinated before parturition, and calves were vaccinated at 2 to 3 months of age. None of the cattle was vaccinated for 1 year preceding and 1 year after the 2 years in which cattle were vaccinated. There was a significantly (P less than 0.05) lower percentage of infectious bovine keratoconjunctivitis (IBK) in calves during years cattle were vaccinated than during years cattle were not vaccinated. During years cattle were vaccinated, there were lower percentages of IBK in vaccinated calves when compared with the percentages of IBK in nonvaccinated calves. When calves were compared on the basis of selection lines, regardless of the vaccination group, there were consistent differences in the percentages that developed IBK. Although calves with pigmented and nonpigmented eyes (representing all 4 genetic lines) developed IBK, the genetic line of calves with the most pigmented eyes had the lowest (P less than 0.05) percentage of IBK. Also, across all genetic lines, there was less IBK in pigmented eyes than in nonpigmented eyes. Seemingly, vaccination of dams, before parturition, and young calves reduced the occurrence of severe IBK in a herd situation under natural exposure conditions. The resistance or susceptibility in cattle under good management may be influenced by genetic factors.

Infectious bovine keratoconjunctivitis: comparison of infection, signs of disease and weight gain in vaccinated versus nonvaccinated purebred Hereford heifer calves.

To determine whether the carrier state of Moraxella bovis could be prevented under natural conditions of exposure by vaccination, purebred Hereford calves were vaccinated twice; once in June 1982, and again in September 1982. Eyes of calves were examined for signs of infectious bovine keratoconjunctivitis (IBK) and cultured for M. bovis in June 1982, September 1982, January 1983 and June 1983. When calves were compared on the basis of selection lines (four genetic groups), there were significant (P less than 0.05) differences in the percentages of infection, disease and weight gain between selection line calves, regardless of their vaccination status. Results suggest that vaccination, in conjunction with clinical infectious, bovine keratoconjunctivitis, reduces the carrier state of M. bovis in the herd but the immunity lasted less than 9 months. The disproportionate representation of the most genetically resistant calves among nonvaccinated calves probably accounted for the equivocal results between vaccinated and nonvaccinated calves.

Reproductive problems associated with bluetongue virus activity in Nebraska.

Abortions, stillborn calves, neonatal mortalities and excessive numbers of weak, slow-starting newborn have contributed to significant losses within the valuable breeding herds at the Roman L. Hruska U.S. Meat Animal Research Center. Conception rates of 70 to 80%, abortion storms and neonatal mortality of 5 to 25% have been observed. Vaccination programs control most of the common diseases that contribute to production losses. Management and nutrition are considered adequate. Excessive dystocia is thought to contribute to some of the excessive losses reported. Diagnostic efforts and epidemiological studies indicate that bluetongue virus (BTV) appears to be associated with some of the reproductive losses. Serotypes 11 and 13 have been isolated. Bovine virus diarrhea virus has also been isolated from weak calves that die at birth or shortly after birth. Serological studies reveal a periodically high incidence of bluetongue (BT) positive breeding animals. Collaborative efforts continue and must be expanded to further elicit the cause and economic impact of reproductive loss at the Meat Animal Research Center.

Infectious bovine keratoconjunctivitis in cattle vaccinated and medicated against Moraxella bovis before parturition.

A vaccination and prophylactic treatment study for infectious bovine keratoconjunctivitis (IBK) was conducted on selection line purebred Hereford and recombination mixed-breed cattle. In February, prepartum cows were allotted to 4 groups: group 1--mixed-breed cows vaccinated with a formalin-killed trivalent Moraxella bovis bacterin; group 2--Hereford cows vaccinated and treated with tylosin; group 3--Hereford cows treated with tylosin; and group 4--mixed-breed cows neither vaccinated nor treated (controls). Groups 2 and 3 were pastured together greater than 3 km for other cattle; cattle added to groups 2 and 3 were treated before being added. Groups 1 and 4 cattle were pastured together; cattle added to groups 1 and 4 were not treated. Cows, and subsequently their calves, were observed cursorily for clinical signs of IBK during the spring and early summer. The eyes of calves were examined in September and October 1979, and their eye secretions were examined for M bovis. The first clinical signs of IBK were seen in the herds in late July, and the largest percentages of acute disease were seen in mid-August. There were no significant differences (P = 0.18) in the percentages of calves that developed IBK, regardless of whether (or not) their dams were vaccinated. A larger percentage of the calves from tylosin-treated cows developed IBK than did calves from nontreated cows. The smallest percentage of disease was seen in calves of cows that were vaccinated only, but the differences were not significant (P greater than 0.10). The percentages of isolations of M bovis were similar (P = 0.23) among the 4 groups of calves. When compared on the basis of breed, the percentage of Hereford calves (62%) that developed IBK was greater than that of the mixed-breed calves (47%). When compared on the basis of color pattern, the percentages with IBK were significantly different (P less than 0.001). The percentages of IBK in calves were: red white-face (70%), black white-face (52%), black black-face with some white on body (40%), black (34%), and others (all color patterns not conforming to the 4 other groups; 21%). When compared on the basis of sire, the percentages of IBK in Hereford calves were significantly different (P less than 0.05). The percentages of affected calves ranged from 80% to 31%; the percentages of affected eyes ranged from 67% to 22%. When compared on the basis of sire, the percentages of IBK in mixed-breed calves were significantly different from each other (P less than 0.001). The percentages of affected calves ranged from 63% to 27% and the percentages of affected eyes ranged from 49% to 16%.

Who should regulate the care of farm animals used in research? an opinion of USDA scientists and administrators.

The humane treatment and care of farm animals used for research purposes is the responsibility of every person associated with their use. Farm animal research is vastly different from laboratory animal research and, therefore, rigid standards and regulations for treatment and care will be difficult to define and administer. The present system of "self regulation" used at USDA farm animal research centers if providing an acceptable method of ensuring adequate animal treatment and care.

Xylazine-induced hyperglycemia in beef cattle.

Intravenous administration of xylazine to beef cattle (10 animals, 0.2 mg/kg of body weight) resulted in rapid onset (less than 15 minutes) of hyperglycemia. Plasma glucose values increased to 195 +/- 15 mg/dl and 305 +/- 10 mg/dl at 15 minutes and 3 hours, respectively. Concomitantly, plasma insulin concentrations dropped from 23 +/- 2 microU/ml before xylazine to 5.8 +/- 0.7 microU/ml and 2.4 +/- 0.3 microU/ml at 15 minutes and 3 hours, respectively. Parallel decreases (20%) were observed for percentage of hemoglobin, red blood cell number, and packed cell volume. Plasma urea nitrogen was significantly (P less than 0.01) incrased within 3 hours of xylazine administration (6.7 +/- 0.9 mg/dl vs 11.4 +/- 0.7 mg/dl). Marked changes in concentrations of plasma-free fatty acids were not observed. Alternative means of anesthesia must be considered in those instances in which biopsy material is to be used for studies of carbohydrate metabolism in vitro.