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Abstract

Objective

To evaluate the efficacy of orally administered tylosin phosphate for prevention and treatment proliferative enteropathy (PE) in pigs.

Animals

Crossbred pigs weaned at 24 days of age.

Procedure

Pigs were challenge exposed with an inoculum of Lawsonia intracellularis strain LR189/5/83- Seven control pigs received buffer solution. Of 33 challenge-exposed pigs, 8 were untreated. Two groups of challenge-exposed pigs were dosed orally with tylosin phosphate via a 2% stabilized premix, starting with 100 or 40 ppm 4 days before challenge exposure and continuing for 16 days, when the dose was reduced to 40 or 20 ppm, respectively, which was continued for 12 more days. Another group of challenge-exposed pigs was dosed orally with 100 ppm of tylosin phosphate commencing 7 days after challenge exposure and continuing for 21 days. Pigs were euthanatized and necropsied 4 weeks after challenge exposure.

Results

The 8 untreated pigs had reduced weight gain; 3 of them had moderate diarrhea 3 weeks after challenge exposure. Five pigs had gross lesions of PE at necropsy. Seven pigs had histologic lesions of PE with numerous L intracellularis organisms. None of the pigs in the control, nonchallenge-exposed, or the 3 groups given tylosin phosphate before or after challenge exposure had clinical signs or lesions of PE.

Conclusion and Clinical Implications

Tylosin phosphate can be effective for prevention and for treatment of PE, using reported dosing schedules. We can experimentally induce PE, using the pure culture challenge-exposure model, for use in testing of treatments. (Am J Vet Res 1997;58:136–139)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether vaccine virus is found in serum and semen of vaccinated boars, whether vaccination prevents subsequent shedding of wild-type virus after challenge exposure, and whether semen and blood variables are altered after vaccination or challenge exposure with wild-type virus, or both.

Design

Throughout the 50-day postvaccination period, serum and semen from exposed boars were evaluated for the presence of porcine reproductive and respiratory syndrome virus (PRRSV). All boars were then challenge-exposed with PRRSV isolate VR-2332 and evaluated for an additional 27 days. Semen quality variables, serostatus, and blood variables were monitored.

Animals

7 PRRSV-seronegative adult boars.

Procedure

Semen was collected 3 times weekly and evaluated by use of a nested reverse-transcriptase polymerase chain reaction for detection of PRRSV RNA. Serum was obtained weekly and evaluated by nested reverse-transcriptase polymerase chain reaction, virus isolation, and PRRSV ELISA. Semen quality variables were evaluated 3 times weekly, and CBC was performed weekly.

Results

Vaccine virus was shed in the semen of all vaccinated boars, but shedding was of shorter duration in 4 of 5 vaccinated boars than that generally observed after exposure to wild-type virus. After challenge exposure, shedding of wild-type virus in semen was shortened or eliminated in 4 of 5 vaccinated boars. Percentage of forward movement and normal spermatozoal morphology and motility were significantly reduced in vaccinated boars after challenge exposure.

Conclusions

Vaccine virus was shed in semen of vaccinated boars, but vaccination generally reduced or eliminated shedding of wild-type PRRSV after challenge exposure. Semen quality appeared to be less than optimal, particularly after vaccination and subsequent challenge exposure with wild-type virus.

Clinical Relevance

Extra-label use of the PRRSV vaccine in boars remains controversial because some boars may still shed wild-type virus in semen after challenge exposure at postvaccination day 50. Semen quality also appeared to be altered after vaccination and subsequent challenge exposure. (Am J Vet Res 1997;58:40–45)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To elucidate kinetics of Bartonella henselae bacteremia and IgG response, evaluate antibiotic therapy, and investigate challenge exposure in cats.

Animals

Specific-pathogen-free cats.

Procedure

Cats were inoculated with B henselae or B quintana and monitored. Convalescent cats were challenge exposed with B henselae. Amoxicillin, enrofloxacin, erythromycin, and tetracycline HCI were evaluated for effect on B henselae bacteremia.

Results

Cats developed B henselae bacteremia within 1 week; bacteremia persisted for longer than 2 months before subsiding spontaneously. IgG antibody titer developed shortly after onset of bacteremia; antibody coexisted with bacteremia for several weeks and remained detectable after bacteremia subsided. Cats inoculated with B quintana remained abacteremic. On challenge exposure to B henselae, cats previously infected with B henselae remained abacteremic; cats previously inoculated with B quintana supported B henselae infection. Tetracycline HCI and erythromycin depressed B henselae bacteremia; however, duration of bacteremia remained similar to that in untreated cats. Obvious signs of illness were not observed.

Conclusions

Long-duration, high-titer B henselae infections were highly reproducible in cats. Convalescent cats were immune to reinfection. B quintana-inoculated cats did not have evidence of infection and were susceptible to B henselae challenge exposure. Antibiotic therapy was incompletely efficacious in terminating cat bacteremia.

Clinical Relevance

A cat with an inapparent B henselae infection must provisionally be regarded as a possible reservoir for infection for a minimum of 2 to 3 months. Convalescent cats are resistant to reinfection. Usual antibiotic therapy was not completely efficacious. Measurement of IgG antibody can be used to detect past or current infection. (Am J Vet Res 1996;57:1714–1719)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To analyze the antigenic cross reactivity of various proteins of strains of Chlamydia pecorum, C psittaci, and C trachomatis.

Samples and Procedures

Strains FC-Stra and LW-613 of C pecorum; strains B577, Fitz-9, and 6BC of C psittaci, and strain LGV-2 of C trachomatis were studied. Strains of C pecorum were propagated in Georgia bovine kidney cells, and other chlamydial strains were propagated in L cells or Georgia bovine kidney cells. Partially purified chlamydial elementary bodies propagated in RAG cells, a BALB/c cell line cloned from a renal adenocarcinoma of BALB/c mice, were used to immunize BALB/c mice for production of monoclonal antibodies. Rabbits were inoculated with yolk sack-propagated, purified elementary bodies to produce polyclonal antisera. The reaction of monoclonal antibodies and polyclonal antisera with chlamydial proteins was analyzed by use of immunoblot techniques.

Results

Two monoclonal antibodies reacted with a 90-kd protein of C psittaci and a 94-kd protein of C pecorum strains. One monoclonal antibody reacted strongly with a 67-kd protein of C pecorum and strain B577 of C psittaci, but weakly with proteins of strains 6BC and LGV-2. Another monoclonal antibody reacted with a 46-kd protein of 2 C pecorum strains and of strain B577 of C psittaci, but not with those of strains 6BC and LGV-2. Two monoclonal antibodies reacted with a 20-kd protein of C pecorum and a 22-kd protein of C psittaci and LGV-2 strains. Polyclonal antisera reacted similarly with the proteins identified by monoclonal antibodies in the various chlamydial strains.

Conclusions

Reactions of several monoclonal antibodies with chlamydial antigens indicated that 67- and 46-kd proteins contain genus- and species-specific epitopes, respectively; a 94-kd protein of C pecorum is homologous to a 90-kd protein of C psittaci and C trachomatis strains; and a 20-kd protein of C pecorum corresponds to a 22-kd protein of C psittaci and C trachomatis. (Am J Vet Res 1996;57:1720–1725)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether Mycobacterium paratuberculosis could survive in colostrum after pasteurization. Additionally, this study investigated the effect pasteurization had on IgG concentration in colostrum.

Animals

Colostrum samples were collected from cattle (beef and dairy) owned by the state of Ohio.

Procedure

Colostrum was divided into aliquots and inoculated with variable concentrations of M paratuberculosis (ATCC No. 19698: 104, 103, and 102 colony-forming units/ml). Half the samples at each concentration were subjected to pasteurization temperatures (63 C) for 30 minutes and the remainder were kept at approximately 20 to 23 C. All samples were incubated (Herrold's egg yolk medium with and without mycobactin J) and observed for growth during the next 16 weeks. Additionally, the IgG concentration of colostrum was determined by radioimmunoassay before and after pasteurization. Samples that coagulated at pasteurization temperatures were mechanically resuspended before measurement of IgG concentration.

Results

Growth of M paratuberculosis was retarded but not eliminated by pasteurization. Growth was observed in all unpasteurized samples incubated on Herrold's egg yolk medium with mycobactin J but in only 2 of 18 pasteurized samples similarly cultured. Growth from pasteurized samples appeared 5 to 9 weeks after growth was observed from nonpasteurized samples.

Mean colostral IgG concentration was 44.4 g/L in nonpasteurized samples and 37.2 g/L in pasteurized sample, a decrease of 12.3%. High-quality colostrum (> 48 g of IgG/L) had a significantly greater loss of IgG concentration than did colostrum of lesser quality (P = 0.002).

Conclusions

Pasteurization lessened, but did not eliminate, growth of M paratuberculosis from experimentally inoculated colostrum samples. Pasteurization resulted in a significant decrease in colostral IgG concentration but not to an unmanageable level that would preclude the colostrum's use for passive transfer of immunity.

Clinical Relevance

Colostrum is macrophage rich and may serve as a source of M paratuberculosis infection to calves. Pasteurization of colostrum may lessen the risk of infection, but will not totally eliminate M paratuberculosis. (Am J Vet Res 1996;57:1580–1585)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To quantify the serum antibody responses to Pasteurella multocida A:3 outer membrane proteins (OMP) for cattle vaccinated with the homologous serogroup and to correlate those responses with the extent of experiment tally induced pneumonia.

Animals

29, 5- to 8-month-old beef-type calves.

Procedure

Calves were vaccinated SC or by aerosol exposure on davs 0 and 7 with live or killed P multocida or phosphate-buffered saline solution (control) and subsequently challenge exposed with virulent P multocida. Antibody responses to P multocida A:3 outer membranes were quantified, using an ELISA. Antibody responses to individual OMP were detected by immunoblot analysis (western blot) and were quantified by densitometry. Antibody responses were compared among groups of calves and for various times after vaccination. Regression analyses were used to determine whether significant correlations existed between lesion scores and antibody responses to either whole outer membranes or to individual OMP

Results

By ELISA, antibody responses to outer membranes for calves aerosol vaccinated with live P multocida were significantly (P < 0.05) greater than those for control calves or for killed P multocida vaccinates. There was a significant (P<0.05) correlation between lesion score and antibody responses to outer membranes. By western blotting and densitometry, antibodies to 11 prominent OMP (100, 97, 90, 85, 74, 53, 46 35, 32, 21, and 16 kd) were identified and quantified. In experiment 1, SC vaccination with live P multocida increased antibody binding to all protein bands except 85- 74-, and 35-kd bands. Aerosol vaccination with live P multocida stimulated increases in antibody binding to all bands except 100 and 16 kd. Antibody responses to the 97-, 90-, 74-, and 35- kd bands were significantly (P <0.05) greater for live aerosol vaccinates than for control calves. In experiment 2, antibody responses were not different between the killed P multocida vaccinates or control calves. Antibody responses for live P multocida aerosol vaccinates were significantly (P <0.05) greater than those for control calves for the 100-, 90-, 85-, 74-, 53-, 35-, and 16-kd bands. Regression analyses indicated significant correlations (P <0.05) between lesion score and antibody responses to the 100-, 90-, 53-, 46-, 35-, and 32-kd OMP.

Conclusions

Several OMP of P multocida type A:3 may be important for stimulating immunity to the organism in cattle. (Am J Vet Res 1996;57:1453-1457)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To investigate the degree of polymorphism in the pulsed-field gel electrophoresis (PFGE) patterns of Staphylococcus intermedius and to assess the value of this typing method for discriminating strains.

Sample population

52 S intermedius isolates from diseased and healthy dogs.

Procedure

Chromosomal DNA of S intermedius was digested with restriction endonuclease Sma I, and the fragments were separated by PFGE in a 1 % agarose gel.

Results

Sma I cut the chromosomal DNA into 15 to 23 fragments ranging from about < 1 to 679 kb, and most of the detectable fragments were < 155 kb. Nine fragments, 115, 48, 33, 26, 16, 13, 10, 4, and < 1 kb, were shared by all or almost all (> 71 %) of the strains examined. Of the 52 strains, each had a different pattern. S intermedius had a high degree of restriction fragment length polymorphism. The PFGE patterns obtained for S intermedius were stable and reproducible when the strains were tested in the different experiments.

Conclusions

Genomic DNA fingerprinting by PFGE is an effective technique for discriminating S intermedius strains. The PFGE method appears to be a useful molecular marker for epidemiologic or ecologic studies of S intermedius. (Am J Vet Res 1996;57:1458-1462)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy calves at the farm and through the marketing process, and to determine the effect of vaccination on PH colonization of the upper respiratory tract and on the incidence of respiratory tract disease (RTD).

Animals

2- to 5-month-old calves (n = 104) from 4 farms.

Procedure

Calves were vaccinated with a killed PH serotype-1 product. Nasal secretion and tonsil wash specimens were cultured for PH, and serum antibody was measured by indirect hemagglutination. Calves with RTD were treated with tilmicosin phosphate.

Results

At the feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH serum titer at the farm, but was not influenced by vaccination. Isolations of PH serotype 1 however, were reduced by vaccination. The major serotypes of PH encountered were 1 and 6.

Conclusion

Vaccination can reduce the frequency of colonization of the uoper respiratory tract by PH. (Am J Vet Res 1936;57:1317-1320)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effectiveness of Pasteurella haemolytica biovar A, serovar 1 (Ph A1) killed by UV light and incorporated with an oil adjuvant or carriers.

Animals

40 weanling male Spanish goats.

Procedure

Goats were randomly allotted to 1 of 6 treatment groups: 4 Ph A1 bacterins (agar beads, polyacrylate beads [PA], phosphate-buffered saline solution, Freund's incomplete adjuvant), live Ph A1 with polyacrylate beads (LiPhPA), and polyacrylate beads (UnVac). Each of 4 Ph A1 vaccines was administered SC twice, 21 days apart, to 1 of 4 groups; another group received only PA beads SC, and the last group received live Ph A1 with PA beads by transthoracic injection into the left lung. 14 days after the second vaccination, all goats were challenge exposed with live Ph A1 by transthoracic injection into the right lung, and 4 days later, all goats were euthanatized and necropsied.

Results

Mean volume of consolidated right lung tissue was 1.02 cm3 for the LiPhPA group, 168.1 cm3 for the UnVac group, 2.3 cm3 for the Freund's incomplete adjuvant bacterin group, 5.53 cm3 for the PA bacterin group, 9.01 cm3 for the agar beads bacterin group, and 7.51 cm3 for the phosphate-buffered saline solution bacterin group. Mean volume of consolidated lung tissue was significantly different between the UnVac group and the other 5 groups.

Conclusion

The LiPhPA group and 4 bacterin groups developed protective immunity against live Ph A1 challenge exposure.

Clinical Relevance

An SC administered, UV light- killed Ph A1 bacterin induced protective immunity equal to that induced by virulent live Ph A1 injected into the target organ, the lung. (Am J Vet Res 1996;57:1168-1174)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To ascertain whether dogs are naturally infected with Ehrlichia chaffeensis.

Animals

74 dogs from 5 animal shelters and 1 kennel in 3 cities and 3 counties in southeastern Virginia were tested during June 1991.

Procedure

Blood was drawn from 74 dogs; 73 were tested serologically for antibodies reactive to E chaffeensis and E canis, and 38 were tested for the presence of E chaffeensis, E canis, and E ewingii by polymerase chain reaction (PCR). Serologic testing by indirect fluorescent antibody assay. Nested PCR used Ehrlichia-wide outside primers to detect initial products, followed by use of species-specific primers for identification.

Results

28 (38.4%) dogs had a positive test result (minimum titer, ≥ 1:64) for antibodies reactive to E chaffeensis, and 28 (38.4%) had a positive reaction to E canis. PCR analysis indicated that 8 (42.1 %) dogs were positive for E chaffeensis and 6 dogs (31.6%) were positive for E ewingii. All dogs had negative results of the PCR test for E canis.

Conclusion

Dogs are potential reservoirs of E chaffeensis.

Clinical Relevance

Canine E chaffeensis infection may be more prevalent than E canis or E ewingii infection in this region of the United States. (Am J Vet Res 1996;57:1175-1179)

Free access
in American Journal of Veterinary Research