Relatedness of cytotoxins from geographically diverse isolates of Moraxella bovis

To determine whether amino acid sequence variation exists in the Moraxella bovis (M. bovis) cytotoxin (MbxA) from geographically diverse M. bovis isolated in the United States, mbxA was amplified and sequenced. The MbxA deduced amino acid sequence from M. bovis originally isolated in California, Washington, North Carolina, and Georgia, as well as reference strains of M. bovis isolated at the National Animal Disease Laboratory, Ames, IA, USA, all encoded a nearly identical 927 amino acid protein. MbxA from two of the four California isolates (SFS 9a and SFS 100a) differed from all other isolates at two sites at which the polar amino acids glutamine (position 666) and asparagine (position 823) were replaced by ionized amino acids glutamic acid and aspartic acid, respectively. Rabbit antiserum to the expressed carboxy terminus (amino acids 590-927) of MbxA from M. bovis (Tifton I) neutralized the hemolytic activity of SFS 9a and SFS 100a. The M. bovis cytotoxin appears to be conserved amongst geographically diverse isolates of M. bovis from the USA. Antiserum against the carboxy terminus of MbxA common to the majority of isolates neutralized the hemolytic activity of two strains with a divergent MbxA deduced amino acid sequence. Vaccines against IBK that incorporate MbxA as antigen may offer protection against geographically diverse strains of M. bovis.     

Recombinant <Emphasis Type="Italic">Moraxella bovoculi</Emphasis> cytotoxin-ISCOM matrix adjuvanted vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis

A randomized, blinded, controlled field trial was conducted during summer 2006 in a northern California, USA, herd of beef cattle to evaluate the efficacy of a recombinant Moraxella bovoculi cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK; pinkeye). A convenience sample comprised of 127 steers were administered a subcutaneous dose of either adjuvant alone (ISCOM matrices; control group) or recombinant M. bovoculi cytotoxin carboxy terminus adjuvanted with ISCOM matrices (MbvA group) and were boostered 21 days later. The steers were examined once weekly for 15 weeks for evidence of IBK. No significant difference in the cumulative proportion of corneal ulcerations was detected between groups. Compared to the control calves, the MbvA vaccinates had significantly higher increases in serum neutralizing titers to M. bovoculi hemolysin between week 0 and week 6. The prevalence of M. bovis isolations was higher from ulcerated eyes of calves vaccinated with MbvA as compared to control calves. Vaccination of calves against the carboxy terminus of M. bovoculi RTX toxin resulted in significant increases in serum hemolysin neutralizing titers and may modulate organism type cultured from ulcerated eyes of calves in herds where both M. bovis and M. bovoculi exist. Use of M. bovoculi antigens alone in vaccines to prevent IBK may not be beneficial in herds where IBK is associated with both M. bovoculi and M. bovis.     

Identification and characterization of complete RTX operons in Moraxella bovoculi and Moraxella ovis

To determine if Moraxella bovoculi (M. bovoculi), a recently characterized coccoid Moraxella that was isolated from the eyes of calves affected with infectious bovine keratoconjunctivitis (IBK), and Moraxella ovis (M. ovis), originally isolated from sheep with conjunctivitis, possessed genes encoding RTX proteins, genomic DNA was amplified with oligonucleotide primers targeting RTX operon genes of Moraxella bovis (M. bovis). Complete classical RTX operons composed of RTXCABD genes closely linked to a putative secretion accessory protein encoding gene (tolC) were identified in M. bovoculi and M. ovis and were designated mbvCABDtolC and movCABDtolC, respectively. These genes were closely related to M. bovis mbxCABDtolC. Polyclonal rabbit antiserum against the carboxy terminus of M. bovoculi MbvA neutralized hemolytic activity of both M. bovoculi and M. ovis; this antiserum did not neutralize the hemolytic activity of M. bovis. M. bovoculi and M. ovis possess genes that encode proteins related to pathogenic factors of M. bovis.     

Differentiation of Moraxella bovoculi sp. nov. from other coccoid moraxellae by the use of polymerase chain reaction and restriction endonuclease analysis of amplified DNA.

Moraxella ovis was historically the only coccoid Moraxella identified in cultures of ocular fluid from cattle with infectious bovine keratoconjunctivitis (IBK) and could be morphologically and biochemically differentiated from Moraxella bovis. Moraxella bovoculi sp. nov. is a recently characterized Moraxella isolated from ulcerated eyes of calves with IBK in northern California in 2002. Like Moraxella ovis, M. bovoculi sp. nov. is a gram-negative coccus/diplococcus. All 18 original isolates of M. bovoculi sp. nov. possessed phenylalanine deaminase (PADase) activity and could therefore be differentiated from M. ovis and M. bovis. During the characterization of 44 additional isolates of hemolytic gram-negative cocci that were cultured from ulcerated eyes of IBK-affected calves, 2 PADase-negative isolates were identified that could not be differentiated biochemically from M. ovis; however, the DNA sequence of the 16S-23S intergenic spacer region (ISR) of the isolates matched the 16S-23S ISR DNA sequence of M. bovoculi sp. nov. To facilitate the identification of PADase-negative moraxellae, a polymerase chain reaction (PCR) coupled with restriction enzyme digestion analysis of amplified DNA was developed. Amplification of the 16S-23S ISR followed by AfaI digestion of amplified DNA could differentiate M. bovoculi sp. nov. from M. ovis and other moraxellae. The DNA sequence analysis of the amplified 16S-23S ISR from the 42 PADase-positive isolates of hemolytic gram-negative cocci indicated that all were M. bovoculi sp. nov. and all possessed an AfaI site. A PCR coupled with restriction analysis of amplified DNA can aid in identifying M. bovoculi sp. nov.     

Effectiveness of a cytolysin-enriched vaccine for protection of cattle against infectious bovine keratoconjunctivitis

OBJECTIVE: To determine the immunogenicity of a Moraxella bovis cytolysin-enriched vaccine for prevention of infectious bovine keratoconjunctivitis (IBK). ANIMALS: 104 mixed-breed beef calves ranging between 4 and 8 months of age. PROCEDURE: Vaccines were prepared by the diafiltration of broth culture supernatant from hemolytic M bovis or sterile media. The diafiltered retentate was combined with Quil A adjuvant. Calves were randomly assigned to receive either the cytolysin vaccine (n = 35) or, as controls, adjuvant (35) or saline (0.9% NaCl) solution (34). Eyes of all calves were examined weekly for signs of IBK for 15 weeks. Calves that developed severe IBK were treated SC with florfenicol. RESULTS: Cytolysin vaccine contained 4 proteins with molecular masses ranging between 65 and 90 kd. Cytolysin-vaccinated calves had fewer instances of IBK than control calves. The time of onset of corneal lesions in cytolysin-vaccinated calves that developed IBK was delayed, compared with that of calves in either control group. The cytolysin-Quil A vaccine contained endotoxin, but calves did not have clinical signs of illness after vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Calves that were vaccinated with a cytolysin-enriched vaccine had some resistance to IBK. Vaccines containing concentrated diafiltered M bovis cytolysin could protect beef calves against IBK.     

Vaccination against infectious bovine keratoconjunctivitis: protective efficacy and antibody response induced by pili of homologous and heterologous strains of Moraxella bovis

The protective effect of 2 Moraxella bovis pili vaccines against infectious bovine keratoconjunctivitis (IBK) experimentally induced by homologous or heterologous strain challenge with virulent, haemolytic M. bovis strain, Dal 2d, was measured in trials using weaned calves aged 3 to 7 months. Purified pili vaccines were prepared from haemolytic strain Dal 2d, (pilus serogroup IV), and haemolytic strain Epp 63, (pilus serogroup III). Calves were challenged by conjunctival instillation of 1 x 10(9) colony forming units of virulent M. bovis strain Dal 2d 14 days after the second of 2 subcutaneous doses of vaccine. Each consisted of 200 micrograms of pili in alum-oil adjuvant administered at an interval of 21 days. In trial 1 the level of protection against challenge with the homologous strain was 46.7% (p less than 0.01). Small, rapidly resolving lesions of IBK occurred in some vaccinates compared with a larger proportion of severe lesions that required treatment in non-vaccinated calves (p less than 0.025). In trial 2, the level of protection against IBK after exposure of vaccinates to the homologous Dal 2d strain was 72.7%, but no significant level of protection or reduction in the size and duration of lesions was apparent in similarly challenged calves vaccinated with Epp 63 pili when contrasted with susceptible, non-vaccinated controls. No marked reduction in the duration of infection with M. bovis Dal 2d following challenge resulted from vaccination with pili of either of the serogroups III or IV. Rising homologous serum IgG antibody titres to serogroups III and IV pili were recorded in response to vaccination with each antigen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunogenicity of a Moraxella bovis bacterin containing attachment and cornea-degrading enzyme antigens

An adjuvanted Moraxella bovis bacterin containing attachment antigens and cornea-degrading enzyme antigens protected cattle from infectious bovine keratoconjunctivitis (IBK) when experimentally challenged with homologous and heterologous challenge cultures of M. bovis. This bacterin also protected cattle against field exposure to M. bovis. Transmission electron microscopy and fluorescein labeled anti-M. bovis pili antiserum showed pili on the M. bovis bacterin strain. Scanning electron microscopy demonstrated a fibrillar glycocalyx. The bacterin strain of M. bovis, but not all strains of M. bovis, destroyed bovine corneal cell monolayers in vitro. Bovine corneal cells began to separate from each other within 5 min after M. bovis organisms were added and adhered to the cell monolayers. Moraxella bovis organisms remained attached to the disintegrating cells as the cell membrane separated and was digested. Vaccination stimulated bacterial agglutination antibodies. However, protection against experimental challenge was more closely related to the cornea-degrading enzyme content of the experimental bacterins. Twenty-two of 29 cattle (76%) vaccinated with bacterins containing a relative enzyme activity (REA) greater than 0.4 were protected in a rigorous challenge of immunity test. Only 1 of 21 non-vaccinated calves (5%) was free of IBK. Ninety-two percent (24/26) of calves vaccinated with a bacterin containing a REA greater than 0.29 remained free of IBK following field exposure, whereas 47% (8/17) non-vaccinated calves developed IBK. Only 8 of 12 calves (67%) vaccinated with a bacterin containing a REA of 0.09 remained free of IBK. In a larger field efficacy test consisting of 32 herds in six states, the incidence of IBK in individual herds ranged from 0% to 55%. The overall rate of infection was 11.2%. Vaccination of calves with an M. bovis bacterin that contained a REA of 0.63 reduced the incidence of IBK from 11.2% (217/1931) in the non-vaccinated controls to 4.3% (66/1520) in cattle vaccinated once and to 3.1% (48/1536) in cattle vaccinated twice.     

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.     

Infectious bovine keratoconjunctivitis: experimental induction of infection in calves with mycoplasmas and Moraxella bovis.

Eyes of 14 calves were exposed by conjunctival instillation to cultures of either Mycoplasma conjunctivae (6 calves) or Acholeplasma laidlawii (8 calves). Calves were observed for clinical signs of infectious bovine keratoconjunctivitis (IBK), and eyes were examined for the test organisms by bacteriologic cultural technique for 60 days. Acholeplasma laidlawii became established in the eyes of 5 of 8 calves; M conjunctivae became established in the eyes of 4 of 6 calves. On day 28, eyes of 9 of the 14 calves were exposed by conjunctival instillation to Moraxella bovis, and all developed IBK. Five calves exposed to Moraxenjunctivae or A laidlawii, but not to Mor bovis, did not develop IBK. Four calves not exposed to M conjunctivae or A laidlawii, but exposed to Mor bovis, developed IBK. Mycoplasmas do not have a major role in IBK, but might produce ancillary effects similar to those of infectious bovine rhinotracheitis virus, wind, ultraviolet radiation, dust, and other irritants.     

Molecular and phenotypic analysis of Moraxella spp. associated with infectious bovine keratoconjunctivitis in Uruguay

Infectious bovine keratoconjunctivitis (IBK) is a common ocular disease of cattle, which is generally thought to be caused by Moraxella bovis. However, a recently characterized Moraxella, M. bovoculi, has been isolated from animals with IBK. The aim of this study was to identify and characterize strains of Moraxella spp. obtained from IBK cases in different geographic locations within Uruguay. Ribosomal gene sequencing indicated that there were two groups of isolates that showed homology with either M. bovis or M. bovoculi. Phylogenetic analysis confirmed the presence of two species as the isolates grouped in different branches of the dendrogram. Conventional biochemical characterization did not distinguish between the species; only 9/25 isolates which had genetic homology with M. bovoculi showed any differences in biochemistry.     

Enhancement of infectious bovine keratoconjunctivitis by modified-live infectious bovine rhinotracheitis virus vaccine

The effects of a modified-live infectious bovine rhinotracheitis virus vaccine (administered ocularly or intranasally) on experimentally induced infectious bovine keratoconjunctivitis were evaluated. The modified-live infectious bovine rhinotracheitis virus vaccine was administered to 13 male Holstein calves (intranasally in 4 and ocularly in 9; day 0). Five calves were not vaccinated and served as controls. Calves were examined daily and, starting on day 4, Moraxella bovis was administered ocularly to all 18 calves once daily for 4 days. The eyes of all calves were assigned a clinical score, and the ocular secretions were evaluated for presence of infectious bovine rhinotracheitis virus and M bovis daily until day 19. The severity of the ocular lesions was estimated by scoring the lesions clinically and by determining the protein concentration, myeloperoxidase activity, and WBC count in the tears. By day 5, conjunctivitis, chemosis, and epiphora were observed in all of the calves vaccinated ocularly. The calves vaccinated intranasally developed conjunctival plaques, but did not develop chemosis or photophobia. All of the calves developed keratitis after inoculation with M bovis. The median lesion scores were greater in both groups of vaccinated calves than in the controls. Corneal perforations developed exclusively in the vaccinated calves. The frequency of M bovis isolation from ocular secretions was significantly (P less than 0.05) greater in the vaccinated calves than in the controls. The tears from the intranasally vaccinated calves contained the highest myeloperoxidase activity and WBC count. The mean protein concentration in the tears of vaccinated calves was not significantly different from that in tears of controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serologic response of vaccinated cattle to strains of Moraxella bovis isolated during epizootics of keratoconjunctivitis.

In studies to determine whether there were antigenic differences between strains (isolates) of Moraxella bovis, the sera from vaccinated calves were tested with isolates of M bovis while the calves were experiencing epizootics of infectious bovine keratoconjunctivitis (IBK). Before the epizootics of IBK, the calves were intramuscularly vaccinated with a formalin-killed autogenous M bovis bacterin. During the epizootics, the eyes were examined by cultural technique, and isolates which were obtained were categorized by catalase activity, source (diseased or nondiseased eyes), and reactivity with the various sera. The serum reactivity of the isolates was compared with that of the vaccinal strain. The vaccinal strain and 8 of the 1 5 selected isolates obtained during the 1974 epizootic were catalase negative. Seven of the 15 isolates from the 1974 epizootic and all of the selected isolates from the 1975 epizootic were catalase positive. A significantly higher (P less than 0.01) percentage of calf sera were serologically reactive with the vaccinal strain and other catalase-negative isolates (45.0%) than with catalase-positive isolates (34.8%). The results, although not definitive, suggest that there may be antigenic differences among strains of M bovis. These differences should be considered when cattle are vaccinated against IBK under natural conditions of exposure.     

The protective efficacy of pili from different strains of Moraxella bovis within the same serogroup against infectious bovine keratoconjunctivitis.

Three groups of ten calves were each immunised with a total of 400 micrograms pili prepared from three separate strains of Moraxella bovis in Alhydrogel-oil adjuvant as two divided, equal doses 21 days apart. Groups 1 and 2 each received a monovalent vaccine made from strain 4L and S276R respectively, which belonged to pili serogroup A. Group 3 received vaccine made from pili of strain Maff1, belonging to serogroup F. A further group of ten calves served as non-vaccinated controls. Calves in groups 1 and 2 had developed serogroup A-specific antibody and those in group 3 developed serogroup F-specific antibody, and some evidence of cross-reacting antibody was also detected when measured by an agglutination test using formalin-killed piliated cells of serogroup A strain 4L. Although antibody titres measured against purified pili by ELISA were highest with homologous serogroup antigens, cross-reactive titres to shared epitopes of M. bovis pili were also detected by this method. Ocular challenge of the 40 calves with virulent M. bovis of serogroup A strain S276R was carried out 14 days after the second vaccine dose. All non-vaccinated calves developed infectious bovine keratoconjunctivitis (IBK). The percentage protection in groups 1 (strain 4L) and 2 (strain S276R) was 60% and 80% respectively (P less than 0.05), with mean lesion scores of 0.7 and 0.3 out of a possible 6.0. The percentage protection of calves in group 3 (strain Maff1) was only 30%, with a mean lesion score of 1.4 compared with 2.2 for non-vaccinated controls. The present findings, together with other evidence indicating that immunity to IBK is serogroup-specific, suggest that inclusion of pili from one representative strain from each of the seven Australian and British serogroups in a polyvalent, subunit vaccine should effectively protect the majority of cattle against IBK caused by most field strains of M. bovis encountered in Australia and the United Kingdom.     

Cloning and characterization of a Moraxella bovis cytotoxin gene

OBJECTIVE: To identify the Moraxella bovis cytotoxin gene. PROCEDURE: Hemolytic and nonhemolytic strains of M. bovis were compared by use of western blotting to identify proteins unique to hemolytic strains. Oligonucleotide primers, designed on the basis of amino acid sequences of 2 tryptic peptides derived from 1 such protein and conserved regions of the C and B genes from members of the repeats in the structural toxin (RTX) family of bacterial toxins, were used to amplify cytotoxin-specific genes from M. bovis genomic DNA. Recombinant proteins were expressed, and antisera against these proteins were produced in rabbits. RESULTS: Several proteins ranging in molecular mass from 55 to 75 kd were unique to the hemolytic strain. An open reading frame encoding a 927-amino acid protein with a predicted molecular mass of 98.8 kd was amplified from M. bovis genomic DNA. The deduced amino acid sequence encoded by this open reading frame was homologous to RTX toxins. Antisera against the recombinant carboxy terminus encoded by this open reading frame neutralized hemolytic and cytolytic activities of native M. bovis cytotoxin. CONCLUSIONS AND CLINICAL RELEVANCE: A gene was identified in M bovis that encodes a protein with sequence homology to other RTX toxins. Results of cytotoxin neutralization assays support the hypothesis that M. bovis cytotoxin is encoded by this gene and belongs in the RTX family of bacterial exoproteins. Identification of this gene and expression of recombinant cytotoxin could facilitate the development of improved vaccines against infectious bovine keratoconjunctivitis.     

Evaluation of anti-Moraxella bovis pili immunoglobulin-A in tears following intranasal vaccination of cattle

Infectious bovine keratoconjunctivitis (IBK) is a highly contagious ocular disease of cattle caused by Moraxella bovis (Mb). Parenterally administered immunogens used to prevent the disease do not offer complete protection possibly because they stimulate a poor ocular mucosal secretory response, in which locally secreted immunoglobulin-A (sIgA) is one of the main components. The principal aim of this study was to evaluate by an indirect enzyme linked immunosorbent assay (ELISA), the local ocular mucosal sIgA response against Mb purified pili, produced after intranasal inoculation of experimental vaccines. Pili were adjuvanted by several different adjuvants (QuilA, Marcol Arlacel, Marcol Span, microencapsulated pili with PLGA polymers). Results were compared to sIgA response produced by adjuvant placebo inoculations and by IBK natural infection. Significantly higher anti-pili IgA response (p<0.05) was detected in calves vaccinated intranasally with pili QuilA and pili Marcol Span compared to control calves, although this specific immune response did not seem to be related to protection against Mb infection or typical IBK lesion development.     

Effectiveness of two commercial infectious bovine keratoconjunctivitis vaccines

Two commercially available infectious bovine keratoconjunctivitis (IBK) vaccines were evaluated for their effectiveness in protecting cattle from disease caused by experimental challenge exposure and natural transmission of Moraxella bovis infections. The study was conducted as 2 experiments, using a total of 81 cattle that were culture-negative for M bovis prior to vaccination. In each experiment, young adult cattle were randomly allotted to 4 groups. Each calf in groups 1 and 2 was vaccinated according to the vaccine manufacturer's directions. Groups 3 and 4 were unvaccinated controls. Three weeks after the last vaccination, each calf in groups 1 and 3 was experimentally challenge exposed by dropping a suspension of viable cells of a virulent strain of M bovis directly onto the corneal surface of each eye. Calves in all 4 groups were then commingled in open pastures so that calves in groups 2 and 4 could be naturally exposed to the calves with experimentally induced infections. Each calf was examined for signs of ocular disease on a regular basis by 2 experienced clinicians who scored each eye for severity of disease on the basis of a prearranged scale. Neither clinician was aware of the vaccination or exposure status of the calf nor to which experimental group they belonged. Lacrimal secretions were collected regularly to determine the number of eyes in which the virulent organism became established. Moraxella bovis with bacterial cultural characteristics similar to those of the virulent strain placed in the eyes of groups 1 and 3 was cultured from greater than or equal to 83% of the eyes of calves in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Attachment of Moraxella bovis to calf corneal cells and inhibition by antiserum

An in vitro assay was developed using calf corneal cells to assess the importance of fimbriae in the colonisation of the bovine ocular surface by Moraxella bovis, and the role of fimbrial antibodies in the bovine immune response and resistance to infectious bovine keratoconjunctivitis (IBK). Fimbriae promoted adherence of M. bovis to calf corneal cells in culture; 15 fimbriate isolates, representative of 6 fimbrial serogroups of M. bovis, adhered to the cells whereas 4 non-fimbriate isolates failed to do so. Fimbrial antibodies in hyperimmune rabbit serum inhibited attachment of all fimbriate strains of the homologous fimbrial serogroup but not those of 5 heterologous serogroups. The relevance of these results to the use of a polyvalent fimbrial vaccine in the control of IBK is discussed.     

Mycoplasma bovoculi infection increases ocular colonization by Moraxella ovis in calves

To determine whether infection with Mycoplasma bovoculi increases ocular colonization of cattle eyes with Moraxella bovis and other bacteria, colonization of ocular gram-negative bacteria were measured in eyes of cattle infected with Mycoplasma bovoculi. Strains of Moraxella ovis were chosen because these are among the most commonly isolated species of gram-negative bacteria from cattle eyes. Five strains of M ovis were characterized biochemically and by pilus structure, permitting the recognition of 2 biotypes. All strains were tested in a mouse corneal pathogenicity model. One strain of each biotype was selected for testing in calves. All 5 strains were apathogenic for mice, and the 2 strains tested in cattle did not induce keratitis. Infection of calves with Mycoplasma bovoculi increased the amount and persistence of colonization with the strains of M ovis.     

Detection of Moraxella bovis antibodies in the SIgA, IgG, and IgM classes of immunoglobulin in bovine lacrimal secretions by an indirect fluorescent antibody test.

The relationship between clinical infectious bovine keratoconjunctivitis (IBK) and Moraxella bovis antibodies was evaluated in a herd of calves during one summer. The detection and the distribution of antibody response in lacrimal secretions of beef calves to natural exposure of M bovis were determined by an indirect fluorescent antibody test. Three classes of immunoglobulins--secretory IgA, IgM, and IgG--were monitored in lacrimal secretions over a 5-month period when IBK was enzootic in the herd. The 3 classes of antibody to M bovis were detected in all but 2 calves at the start of the monitoring, and the highest and most persistent M bovis antibody titers were in the IgG immunoglobulin class, and less so in IgM and secretory IgA classes. The specific antibodies present in the lacrimal secretions did not prevent the development of clinical IBK in the calves.