Biomedical subjects

G W Pugh

Publications and source records attributed to G W Pugh.

At least 37 records · Page 2Linked to original sources

PubMed1989

Identification of a virulence factor for Brucella abortus infection in BALB/c mice.

Immunogenic or pathogenic factors of recombinant proteins (rBCSP20, rBCSP-31, and rBCSP45 of Brucella abortus strain 19) for mice were compared with factors of a proteinase K-treated lipopolysaccharide extracted from B abortus strain 2308. Mice were vaccinated with 4 products, using different inoculation schedules and were challenge exposed with a virulent culture of B abortus strain 2308. Blood samples were collected 2 weeks after vaccination and at necropsy and sera were obtained. Spleens were cultured for B abortus at necropsy (3 to 4 weeks after challenge exposure). Mice given proteinase K-treated lipopolysaccharide alone or in conjunction with rBCSP20 or rBCSP45 proteins were protected, but mice given rBCSP31 on the same day as challenge exposure were not. Vaccination with recombinant proteins alone neither provide protection nor significantly (P greater than 0.05) increase the pathogenic effect of the challenge-exposure culture. Seemingly, rBCSP31 might be a virulence factor of B abortus.

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PubMed1987

Pathogenesis of corneal lesions caused by Moraxella bovis in gnotobiotic calves.

Moraxella bovis was instilled into the conjunctival sac of gnotobiotic calves and corneas were sampled serially after infection. Lesions developed in seven of eight infected calves, but were absent in a noninfected control calf. Histologically, M. bovis was first seen in foci of swollen epithelium and within basal epithelial cells adjacent to ulcers. Corneal ulcers were severe in later stages of infection; fibrin deposits, neutrophils, and bacteria were present in the stromas. Examination of early lesions by scanning electron microscopy showed M. bovis in pits on the surfaces of dark epithelial cells, enmeshed in degenerate epithelial cells and within erosions and an ulcer; in later samples, bacteria were rare. Ultrastructurally, M. bovis was seen in surface pits in superficial epithelial cell processes and within swollen epithelial cells. In stroma, M. bovis was frequently seen among collagen fibrils, within neutrophil phagosomes, and associated with cellular debris. This study demonstrates that a virulent strain of M. bovis can invade bovine corneal epithelial cells and can cause keratitis in the absence of injurious ultraviolet irradiation or other known predisposing environmental factors.

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PubMed1987

Conjunctival lesions caused by Moraxella bovis in gnotobiotic calves.

Hemolytic Moraxella bovis was instilled into the conjunctival sac of gnotobiotic calves, and conjunctivae were sampled serially after infection. Bilateral lesions developed in seven of eight infected calves. Histologically, M. bovis was first seen within swollen epithelial cells near the lid margins and occasionally within superficial epithelium in other areas. Conjunctival erosions and ulcers were seen in later stages. Scanning electron microscopy showed M. bovis in pits on surfaces of epithelial cells and in erosions on palpebral conjunctivae; lesions were prominent near lid margins. By transmission electron microscopy, M. bovis was seen within swollen epithelial cells near lid margins; many epithelial cells had undergone cytolysis. This study demonstrates that virulent M. bovis can invade bovine conjunctival epithelial cells and cause conjunctivitis in the absence of injurious ultraviolet irradiation or other predisposing environmental factors.

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PubMed1986

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.

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PubMed1986

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.

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PubMed1986

Use of subcutaneously implanted chambers in calves for in vivo study of isolates of Moraxella bovis.

Selected cultures of Moraxella bovis were studied in calves, using chambers fabricated from a semipermeable membrane supported and protected by perforated plastic golf balls. Plain balls, semipermeable membrane-covered balls, and balls that contained bags fabricated from semipermeable membranes were surgically implanted subcutaneously in calves at a site approximately 25 cm ventral to the paralumbar fossa and cranial to the prefemoral lymph node. After calves recovered from surgery, chambers were inoculated with different cultures of M bovis. Cultural examination of samples taken from inoculated chambers indicated that M bovis cultures were maintained within the chambers for variable times, depending on the characteristics of the culture inoculated. A smooth (piliated) culture dissociated into a rough (nonpiliated) culture after 4 weeks of incubation within a chamber but none of the rough cultures became smooth. The technique offers a method to study the in vivo variations in a series of cultures or strains of microorganisms under the influence of the same host factors. The selective permeability of the chamber may be controlled by using membranes of different porosities to control the flow of entering or exiting dialysate.

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PubMed1986

Identification of bovine carriers of Moraxella bovis by comparative cultural examinations of ocular and nasal secretions.

The carrier state of Moraxella bovis was investigated, using bacteriologic examinations of ocular and nasal secretions from cattle under experimental and natural conditions of exposure and management. Moraxella bovis was isolated throughout the year from the ocular and nasal secretions of cattle naturally affected with infectious bovine keratoconjunctivitis. There was also 1 case of nasal transmission of M bovis without isolation of M bovis from ocular secretions and 1 case of M bovis isolation from the vagina of a calf contracted by contact with a calf affected with infectious bovine keratoconjunctivitis. The frequency of isolations and duration of infections, as determined by examination of ocular and nasal secretions, indicated that these secretions were comparable in the identification of M bovis carriers. The increased cultural isolations of M bovis from nasal secretions after shipment relative to the number of isolations before shipment indicated that shipment may serve as a stress factor causing an increase in the number of carriers.

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PubMed1986

Infectious bovine keratoconjunctivitis: contact transmission.

The transmission of Moraxella bovis was studied in calves in the absence of the face fly (Musca autumnalis) or environmental conditions that might insult the eye. Thirty calves were placed in 10 groups of 1 experimentally infected calf and 2 contact calves each. Over 40 days, only 1 eye in 1 contact calf developed clinical infectious bovine keratoconjunctivitis. The organism was recovered in only 8 of 20 contact calves, whereas infection and disease occurred in all experimentally infected calves. Transmission of M bovis occurring in the absence of some other intervening factor was probably of minimal importance. Seemingly, herd preventive treatment would be most effective when flies and environmental factors are at a minimum.

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PubMed1986

Plasmid profiles of Moraxella bovis isolates.

Two-hundred isolates of Moraxella bovis were selected at random and examined for the presence of plasmid DNA by a rapid alkaline-detergent lysis method. All isolates contained from 1 to 6 plasmids, with varying agarose-gel electrophoretic migration patterns. Most (80%) isolates carried 2 to 4 plasmids, which ranged in molecular weight from 2.6 to 80 megadaltons. Seemingly, plasmid profiles can be used as a simple, reliable epizootiologic tool to establish a strain identification scheme for M bovis.

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PubMed1985

Infectious bovine keratoconjunctivitis: subconjunctival administration of a Moraxella bovis pilus preparation enhances immunogenicity.

To compare the immune response elicited by 3 routes of vaccination, 36 calves were randomly allotted to 4 groups of 9 calves each. Group I was vaccinated subconjunctivally only. Group II was vaccinated concomitantly, both subconjunctivally and in the dewlap. Group III was vaccinated in the dewlap only. Group IV was not vaccinated and served as a virulence control for the Moraxella bovis culture. Calves in groups I, II, and III were given 2 inoculations with 14 days between inoculations. Twenty-one days after the last inoculation, the ventral conjunctival sac of all calves was instilled with cells of a virulent M bovis strain. After challenge exposure, all vaccinated calves (groups I, II, and III) had evidence of enhanced resistance, compared with the nonvaccinated calves. The highest to lowest gradients of immune responsiveness were: Group I greater than or equal to group II greater than group III greater than group IV. When immune criteria, such as the percentage of diseased eyes, the mean duration of infection, the severity of corneal lesions, and the serologic response were compared, groups I and II were significantly (P less than 0.05) more resistant to challenge exposure than were groups III and IV. Group III was significantly (P less than 0.05) different from group IV in severity of lesions and in serologic response. Also, the mean duration of infection was shorter, and the percentage of diseased eyes was less in group III than in group IV (P greater than 0.10). Group I was more resistant than was group II (P less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1984

Evaluation of an indirect hemagglutination inhibition technique for identifying antibody in animals experimentally and naturally exposed to fungi.

Rabbits were exposed to aerosols containing spores of Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, or of a Penicillium sp. Sera from these rabbits were tested by indirect hemagglutination (IHA) and by IHA inhibition. The serologic reactions with the rabbit sera were compared to reactions with sera from cattle naturally exposed to airborne microorganisms. By three months of age, most cattle had positive IHA reactions to A. fumigatus and Penicillium antigens. The IHA inhibition tests indicated that antibody production in 12 of the 20 cattle probably resulted from exposure to A. flavus. One calf reacted as if sensitized by A. niger. Two were totally nonreactive. Five of the cattle had reactions that were not identifiable relative to the reactions in rabbits.

Aerosols↗

PubMed1984

Infectious bovine keratoconjunctivitis: enhancement of Moraxella bovis pili immunogenicity with diphtheria-tetanus toxoids and pertussis vaccine.

A study was conducted to determine whether diphtheria-tetanus-toxoids and pertussis vaccine (DPT) would enhance the immunogenicity of homologous Moraxella bovis pili fractions. Thirty-six calves were divided into 4 groups (I, II, III, and IV) of 9 calves each. Calves in group I were not vaccinated and served as controls. Calves in group II were vaccinated with pili fractions only. Calves in group III were vaccinated with DPT only. Calves in group IV were vaccinated with DPT and pili. Vaccination consisted of 2 inoculations, 21 days apart. Fourteen days after the last vaccinal inoculation was done, the eyes of all calves were exposed to a hemolytic homologous strain of M bovis. The percentage of eyes with disease was significantly less in calves given DPT and pili (P less than 0.001) and calves given pili only (P less than 0.05) than in calves given DPT only or nonvaccinated calves. The lesions were less severe in calves vaccinated with pili only than in calves not vaccinated with pili. Serologic results also showed a positive relationship between the development of serum antibodies against pili and immunity. The results indicate that DPT enhanced the immune response and if used as an adjuvant, might be useful in the development of a vaccine against infectious bovine keratoconjunctivitis.

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PubMed1984

Effects of aflatoxin ingestion on the development of Moraxella bovis infectious bovine keratoconjunctivitis.

A study was conducted to determine whether measured doses of aflatoxin given under different schedules would influence the pathogenesis of Moraxella bovis induced infectious bovine keratoconjunctivitis (IBK). Calves were allotted to 4 groups (groups I-IV) of 9, 9, 9, and 8 calves, respectively. Group I calves were given aflatoxin for 11 consecutive days starting 5 days before their eyes were exposed to M. bovis. Group II calves were given aflatoxin for 5 consecutive days starting 7 days after their eyes were exposed to M. bovis. Group III calves were given aflatoxin for 5 consecutive days starting 21 days after their eyes were exposed to M. bovis. Group IV calves were not given aflatoxin; but their eyes were exposed to M. bovis on the same day as were the eyes of calves in groups I-III; these calves served as controls. Aflatoxin had little if any influence on the pathogenesis of IBK under the conditions of this study. The results did not rule out an exacerbating effect of M bovis infection on aflatoxicosis in calves. Calves with the highest concentration of aflatoxin in their blood had the more severe signs of aflatoxicosis. Possible reasons for the equivocal results are discussed.

Aflatoxins↗

PubMed1983

Infectious bovine keratoconjunctivitis: evidence for general immunity.

A study was conducted to determine whether acquired immunity to Moraxella bovis during episodes of infectious bovine keratoconjunctivitis (IBK) was local or general. Twelve calves (principals) were exposed to M bovis in the left eye by conjunctival sac instillation on day 1 and in both eyes on day 21. Six calves exposed in both eyes at day 1 and six others exposed at day 21 served as controls. The mean duration of infection in the right eyes of principal calves was significantly less (P less than 0.001) than that in the left eyes of principal calves, as well as those of the control calves. There were no significant differences (P less than 0.2) in the durations of infection between the 2 groups of the control calves or the duration of infection in the left eyes of principal calves. Five of 6 calves (7 of 12 eyes) in the day 1 controls and 4 of 6 calves (7 of 12 eyes) in the day 21 controls developed IBK. Ten of 12 of the principals developed IBK in the left eye when exposed on day 1, but only 1 of 12 principals developed IBK in the right eye when exposed on day 21. It was concluded that the resistance to infection after initial infection is probably due to a generalized immune response, rather than to a localized response.

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PubMed1982

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%.

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PubMed1982

Experimental infectious bovine keratoconjunctivitis: efficacy of a vaccine prepared from nonhemolytic strains of Moraxella bovis.

Calves vaccinated with a bacterin prepared from 4 nonhemolytic strains of Moraxella bovis were challenge exposed with a virulent hemolytic strain of M bovis. Ten calves were given 2 vaccinal inoculations 21 days apart. Twenty-one days after the last vaccinal inoculation, the eyes of the 10 vaccinated and the eyes of the 12 non-vaccinated calves were exposed to a hemolytic heterologous strain of M bovis. The percentage of eyes with infectious bovine keratoconjunctivitis was lower, the lesions were less severe, and the duration of infection was shorter in vaccinated calves than in nonvaccinated calves. Seemingly, the resistance induced by nonhemolytic strains of M bovis was at least comparable with the induced by hemolytic virulent strains of that organism. The nature of the immune response in vaccinated calves is discussed.

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PubMed1981

Isolation of Moraxella bovis ribosomes and their subsequent use in a vaccine against infectious bovine keratoconjunctivitis.

A study was conducted to determine whether a Moraxella bovis ribosomal vaccine would protect calves from infectious bovine keratoconjunctivitis (IBK). Each of 16 calves were given 2 inoculations 21 days apart. Twenty-one days after the 2nd inoculation, 8 of the calves were challenge exposed with a homologous strain culture and 8 calves were challenge exposed to a heterologous strain culture of M bovis. Sedimentation velocity analysis of the ribosomes used in this study indicated that they were mostly 30S and 50S subunits. Chemical assays indicated that the ribosomes were composed of 64% to 65% RNA and 35% to 36% protein. The cesium chloride buoyant density of the ribosomes was 1.62 g/ml. Ribosomes used as antigen gave 1 line of precipitation in a gel-diffusion precipitin test with hyperimmune serum against the whole-cell antigen of the homologous strain of M bovis. The eyes of all the experimentally exposed calves became infected and all calves developed clinical signs of either unilateral or bilateral IBK. None of the sera of the vaccinated calves had detectable precipitins against the ribosomal antigen at the time they were challenge exposed, but most of the sera had precipitins against whole-cell and pilus antigens. The results indicate that M bovis ribosomes, although similar to other bacterial ribosomes, did not protect cattle against IBK.

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PubMed1981

Influence of outdoor winter environment on the course of infectious bovine keratoconjunctivitis.

The effect of environmental conditions on the onset, severity, and duration of Moraxella bovis infection and subsequent clinical disease was studied. Twelve calves were used; 6 were maintained under usual isolated experimental conditions (inside), and 6 were kept under normal feedlot conditions (outside) during the winter (-20 to +15 C). The cattle housed inside had a higher infection rate, a milder disease, and longer duration of infection than did the cattle kept out side. Seemingly, the stress of the cold weather caused a more severe disease of shorter duration.

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