A randomized and blinded field trial to assess the efficacy of an autogenous vaccine to prevent naturally occurring infectious bovine keratoconjunctivis (IBK) in beef calves

Randomized controlled field trial to assess the efficacy of an intranasal Moraxella bovis cytotoxin vaccine against naturally occurring infectious bovine keratoconjunctivitis

Background

Infectious bovine keratoconjunctivitis (IBK; pinkeye) is generally considered to be caused by corneal infections with Moraxella bovis. Previous studies demonstrated that M. bovis cytotoxin-specific mucosal immune responses in the bovine eye can be stimulated by intranasal vaccination with a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid.

Methods

A randomized controlled field trial (two-arm parallel design with blinding) was conducted in beef steers in Northern California to determine if this vaccine could prevent naturally occurring IBK and/or reduce morbidity rates associated with this disease. Beef steers were vaccinated intranasally on days 0 and 21 with either a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid (Vaccine group) or adjuvant alone (Control group). Eye examinations were performed on all steers every 7 days for 16 weeks to document the occurrence of IBK and to determine sizes of corneal ulcers. Serum and tear samples were collected on days 0, 42, and 112 from a subset of animals to measure changes in systemic and ocular immune responses to M. bovis cytotoxin.

Results

The cumulative proportion of steers that developed IBK after 16 weeks did not differ between groups. Variables related to disease severity were numerically lower in steers that received the experimental vaccine. IBK-affected Vaccine group steers had a significantly lower number of observation weeks with severe ulcers versus Control group steers. Cytotoxin-specific tear IgA was significantly higher in Vaccine group compared to Control group steers on day 112. Conclusion: Although the proportion of animals that developed corneal ulcers associated with IBK did not differ between groups, the lowered metrics of disease severity in vaccinated steers suggests that intranasal vaccination with recombinant M. bovis cytotoxin can reduce the severity of IBK in cattle.

Investigation of the pathogens contributing to naturally occurring outbreaks of infectious bovine keratoconjunctivitis (pinkeye) using Next Generation Sequencing

Infectious bovine keratoconjunctivitis (IBK), commonly known as pinkeye, has a marked negative impact on the economy of the cattle industry. Moraxella species, including Mor. bovis and Mor. bovoculi, which have been associated with this disease, colonize clinically healthy eyes as well, suggesting that there are intrinsic changes that may occur to the ocular microbiota or the involvement of additional unrecognized organisms that contribute to IBK. To evaluate this, 104 ocular swabs collected from eyes with IBK or clinically healthy eyes from 16 different cattle herds were subjected to 16 S rRNA gene PCR and next generation sequencing (NGS) analysis. Organisms detected were similar across the herds and there was no difference in the total number of bacterial groups detected among IBK cases and controls. However, the percentages of the different organisms detected varied between the two groups, including Moraxella spp., with more Moraxella spp. in eyes with IBK than controls. Further, using culture and whole genome NGS, a new species of Moraxella (suggested name Mor. oculobovii) was detected from the eyes of cattle from two farms. This strain is non-hemolytic on blood agar, is missing the RTX operon, and is likely a non-pathogenic strain of the bovine ocular microbiome. Alteration of the ocular microbiota composition may have a predisposing role, enhancing bacterial infection and the occurrence of clinical IBK. Future studies are required to evaluate if these changes are permanent or if there is a shift in the microbiome following recovery from the infection and how antibiotics might affect the microbiome.

A randomised control trial to evaluate the effectiveness of a commercial vaccine for pinkeye in Australian beef cattle

Pinkeye (a generic term to describe infectious bovine keratoconjunctivitis) is a significant disease of cattle worldwide, impacting productivity and animal welfare. One commercial pinkeye vaccine, a systematically administered Moraxella bovis bacterin, has been available in Australia since 2007. This is the first field trial of the effectiveness of this vaccine for the prevention of naturally occurring disease in Australia. Extensively run beef herds in southwest Queensland that regularly experienced pinkeye were enrolled in the trial and animals were randomly allocated to vaccinated and control groups in different proportions in each herd. The subsequent incidence of clinical pinkeye between the two groups was compared for animals less than one-year-old. Data were analysed from 649 cattle from five herds over two pinkeye seasons: three herds of 390 calves from 1st November 2019 to 20th January 2020 and two herds of 259 calves from 23rd September 2020 to 21st April 2021. Pinkeye was common with 24% of all calves (156/649) contracting the disease during the trial. Univariable and multivariable binary logistic mixed-effect models were fitted to account for clustered data and potential residual confounding due to sex, weight, breed, coat colour, and periocular pigmentation. The incidence of pinkeye was not significantly different between vaccinated and control groups, both alone (p = 0.67) and after adjusting for sex and weight differences (p = 0.69). The vaccine was not protective against naturally occurring pinkeye under the field conditions.

A Five Year Randomized Controlled Trial to Assess the Efficacy and Antibody Responses to a Commercial and Autogenous Vaccine for the Prevention of Infectious Bovine Keratoconjunctivitis

A randomized control trial was performed over a five-year period to assess the efficacy and antibody response induced by autogenous and commercial vaccine formulations against infectious bovine keratoconjunctivitis (IBK). Calves were randomly assigned each year to one of three arms: an autogenous vaccine treatment that included Moraxella bovis (M. bovis), Moraxella bovoculi, and Mycoplasma bovoculi antigens, a commercial M. bovis vaccine treatment, or a sham vaccine treatment that consisted only of adjuvant. A total of 1198 calves were enrolled in the study. Calves were administered the respective vaccines approximately 21 days apart, just prior to turnout on summer pastures. Treatment effects were analyzed for IBK incidence, retreatment incidence, 205-day adjusted weaning weights, and antibody response to the type IV pilus protein (pili) of M. bovis as measured by a novel indirect enzyme-linked immunosorbent screening assay (ELISA). Calves vaccinated with the autogenous formulation experienced a decreased cumulative incidence of IBK over the entire study compared to those vaccinated with the commercial and sham formulations (24.5% vs. 30.06% vs. 30.3%, respectively, p = 0.25), and had less IBK cases that required retreatment compared to the commercial and sham formulations (21.4% vs. 27.9% vs. 34.3%, respectively, p = 0.15), but these differences were not significant. The autogenous formulation induced a significantly stronger antibody response than the commercial (p = 0.022) and sham formulations (p = 0.001), but antibody levels were not significantly correlated with IBK protection (p = 0.37).

Risk factors associated with pinkeye in Australian cattle

Pinkeye is the most important bovine ocular disease worldwide and a major welfare and economic concern to the Australian cattle industry. Pinkeye can occur in epidemic proportions, but severity and susceptibility vary within and between herds, indicating that the disease is multifactorial. This study was conducted to identify the on-farm risk factors associated with pinkeye disease in Australian cattle. Data were gathered from cattle farmers using a custom designed online questionnaire. Farmer responses suitable for assessment (n = 999) were analysed with descriptive, univariable and multivariable logistic regression to evaluate the association of 26 explanatory variables with pinkeye within-herd prevalence. Results revealed that farm location, farm grazing area, farmer-reported dust levels, fly levels, rain levels, animal zebu content and cattle age were significantly associated with pinkeye prevalence. More specifically, having a farm located in southern Australia, of smaller grazing area with cattle ≤ 2 years of age, was associated with a higher pinkeye prevalence. Pinkeye prevalence was also greater if respondents ranked their farms as having high fly levels compared to moderate and low fly levels, respectively and on farms ranked low for rainfall compared to moderate and high rainfall, respectively. Those that ranked their farms as having high dust levels had more pinkeye compared to moderate and low dust levels, but moderate dust levels were protective compared to low dust levels. The results confirm that pinkeye disease is multifactorial and is associated with a range of host and environmental factors. These findings should be used to assist in the control of the disease and improve pinkeye outcomes in Australian cattle.

The Evidence Base for Prevention of Infectious Bovine Keratoconjunctivitis Through Vaccination

Pili and cytotoxins are important virulence factors and antigens for Moraxella spp. Local and systemic immunity may play a role in the body's response to infectious bovine keratoconjunctivitis (IBK). No evidence exists that eliminating the carrier state for IBK is possible or beneficial. Evidence for efficacious transfer of passive immunity from dams to calves is conflicting. Autogenous vaccines and commercial vaccines for putative pathogens for IBK have not yet shown efficacy in blinded randomized field trials. Study design features, such as randomization, blinding, diagnostic criteria, and use of a placebo, reduce the risk of bias in vaccine studies for IBK.

Applying Concepts of Causal Inference to Infectious Bovine Keratoconjunctivitis

Establishing causation, otherwise known as causal assessment, is a difficult task, made more difficult by the variety of causal assessment frameworks available to consider. In this article, Bradford Hill viewpoints are used to discuss the evidence base for Moraxella bovis and Moraxella bovoculi being component causes of infectious bovine keratoconjunctivitis. Each of the nine Bradford Hill viewpoints are introduced and explained: strength, consistency, specificity, temporality, biologic gradient, plausibility, coherence, experiment, and analogy. Examples of how the viewpoints have been applied for other causal relations are provided, and then the evidence base for M bovis and M bovoculi is discussed.

A 2-year randomized blinded controlled trial of a conditionally licensed Moraxella bovoculi vaccine to aid in prevention of infectious bovine keratoconjunctivitis in Angus beef calves

BACKGROUND

Infectious bovine keratoconjunctivitis (IBK) in beef cattle has major welfare and production implications. Effective vaccination against IBK would also reduce antibiotic use in beef production.

OBJECTIVE/HYPOTHESIS

To evaluate the efficacy of a conditionally licensed commercial IBK vaccine containing Moraxella bovoculi bacterin. Primary working hypothesis was that animals vaccinated with 2 doses of the commercial M. bovoculi vaccine would have a lower risk of disease.

ANIMALS

Spring born calves at a university cow-calf herd. After excluding animals with ocular lesions, calves eligible for prevention assessment in 2017 and 2018 were 163 (81 vaccinated, 82 unvaccinated) and 207 (105 vaccinated, 102 unvaccinated). One hundred sixty two and two hundred and six calves completed the follow-up period in 2017 and 2018, respectively.

METHODS

A randomized controlled trial. The trial design was a 2-arm parallel trial with a 1:1 allocation ratio.

RESULTS

In both years, calves receiving the vaccine had more IBK. This effect was small. The pooled risk ratio was 1.30 (95% confidence interval 0.84-2.01). The pooled unadjusted difference in mean weight (kg) at weaning was -0.88 (95% confidence interval-7.2-5.43).

CONCLUSIONS AND CLINICAL IMPORTANCE

We were unable to document that the M. bovoculi bacterin vaccine had a protective effect for the incidence of IBK in our single herd in a 2-year study.

A multiplex real-time PCR assay for the detection and differentiation of five bovine pinkeye pathogens

Infectious bovine keratoconjunctivitis (IBK), also known as pinkeye, is one of the most common eye diseases in cattle. Several pathogens have been associated with IBK cases, however, Moraxella bovis, Moraxella bovoculi, Mycoplasma bovis, Mycoplasma bovoculi and bovine herpesvirus type 1 (BHV-1) are most frequently observed. A multiplex real-time PCR assay using two reactions was developed for the detection and differentiation of these five pathogens. Detection sensitivities of the multiplex assays were compared to singleplex reactions testing for the same targets. Correlation coefficients (R²) of >0.99, and PCR efficiencies between 92 and 106% were demonstrated in all singleplex and multiplex real-time PCR reactions. The limits of detection (LOD) of multiplex assays for Moraxella bovis, Moraxella bovoculi, Mycoplasma bovis, Mycoplasma bovoculi and BHV-1 were 19, 23, 25, 24 and 26 copies per reaction, respectively. No cross amplification was observed for specificity testing of 179 IBK positive clinical samples and 55 non-target clinical samples. Percentage of clinical samples positive for Mycoplasma bovoculi, Moraxella bovoculi, Moraxella bovis, BHV-1 and Mycoplasma bovis were 88.8% (159/179), 75.9% (136/179), 60.3% (108/179), 11.7% (21/179) and 10.0% (18/179), respectively. Moraxella bovis, Moraxella bovoculi and Mycoplasma bovoculi were more prevalent than Mycoplasma bovis and BHV-1 in IBK samples collected from animals in this study population. Our data indicates that the multiplex real-time PCR panel assay is highly sensitive and highly specific for the detection and differentiation of the five major pathogens associated with bovine pinkeye.

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A multiplex real-time PCR is developed for the detection of five major IBK pathogens.

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Correlation coefficients of all standard curves were >0.99.

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PCR amplification efficiencies for the five pathogens were between 92% and 106%.

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Limits of detection were between 19 and 26 copies per reaction for the five pathogens.

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Moraxella bovoculi, Mycoplasma bovoculi, and Moraxella bovis were more prevalent IBK pathogens.

Whole genome sequencing of Moraxella bovoculi reveals high genetic diversity and evidence for interspecies recombination at multiple loci

Moraxella bovoculi is frequently cultured from the ocular secretions and conjunctiva of cattle with Infectious Bovine Keratoconjunctivitis (IBK). Previous work has shown that single nucleotide polymorphism (SNP) diversity in this species is quite high with 81,284 SNPs identified in eight genomes representing two distinct genotypes isolated from IBK affected eyes (genotype 1) and the nasopharynx of cattle without clinical IBK signs (genotype 2), respectively. The goals of this study were to identify SNPs from a collection of geographically diverse and epidemiologically unlinked M. bovoculi strains from the eyes of IBK positive cattle (n = 183) and another from the eyes of cattle (most from a single population at a single time-point) without signs of IBK (n = 63) and to characterize the genetic diversity. Strains of both genotypes were identified from the eyes of cattle without IBK signs. Only genotype 1 strains were identified from IBK affected eyes, however, these strains were isolated before the discovery of genotype 2, and the protocol for their isolation would have preferentially selected genotype 1 M. bovoculi. The core genome comprised ~74% of the whole and contained >127,000 filtered SNPs. More than 80% of these characterize diversity within genotype 1 while 23,611 SNPs (~18%) delimit the two major genotypes. Genotype 2 strains lacked a repeats-in-toxin (RTX) putative pathogenesis factor and any of ten putative antibiotic resistance genes carried within a genomic island. Within genotype 1, prevalence of these elements was 0.85 and 0.12 respectively in strains from eyes that were IBK positive. Recombination appears to be an important source of genetic diversity for genotype 1 and undermines the utility of ribosomal-locus-based species identification. The extremely high genetic diversity in genotype 1 presents a challenge to the development of an efficacious vaccine directed against them, however, several low-diversity pilin-like genes were identified. Finally, the genotype-defining SNPs described in this study are a resource that can facilitate the development of more accurate M. bovoculi diagnostic tests.

Isolation of Moraxella bovoculi from racehorses with keratoconjunctivitis

Moraxella bovoculi was isolated and identified in ocular fluid samples collected from 9 racehorses with infectious keratoconjunctivitis in China in 2013. All 9 M. bovoculi isolates were hemolytic, Gram-negative diplococci that were phenylalanine deaminase positive. The sequence of the 16S ribosomal DNA (rDNA) gene of the isolates matched the 16S rDNA sequence of M. bovoculi. Amplification of the 16S-23S intergenic spacer region followed by AfaI digestion produced a 600-base pair product, a result characteristic of M. bovoculi isolates. The phylogenetic analysis based on the 16S rDNA sequence confirmed the strain isolated in the current study had genetic homology with M. bovoculi.

Randomized blinded controlled trial to assess the association between a commercial vaccine against Moraxella bovis and the cumulative incidence of infectious bovine keratoconjunctivitis in beef calves

OBJECTIVE To assess the association between a commercially available vaccine against Moraxella bovis and cumulative incidence of infectious bovine keratoconjunctivitis (IBK) from processing to weaning (primary objective) and body weight at weaning (secondary objective). DESIGN Randomized blinded controlled trial. ANIMALS 214 calves (≥ 2 months of age) born in the spring of 2015 at an Iowa State University cow-calf research unit with no visible lesions or scars on either eye. PROCEDURES Calves were randomly allocated to receive SC administration of a single dose of a commercial vaccine against M bovis (112 enrolled and 110 analyzed) or saline (0.9% NaCl) solution (111 enrolled and 104 analyzed). Calves were monitored for signs of IBK from treatment to weaning, and body weight at weaning was recorded. People involved in calf enrollment and outcome assessment were blinded to treatment group assignment. Cumulative incidence of IBK and weaning weight were compared between vaccinated and unvaccinated calves; the effect measure was the risk ratio and mean difference, respectively. RESULTS IBK was detected in 65 (59.1%) vaccinated calves and 62 (59.6%) unvaccinated calves (unadjusted risk ratio, 0.99; 95% confidence interval, 0.79 to 1.24) during the study period. No significant difference in weaning weights was identified between vaccinated and unvaccinated calves (unadjusted effect size, 4.40 kg [9.68 lb]; 95% confidence interval, -3.46 to 12.25 kg [-7.61 to 26.95 lb]). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the commercially available M bovis vaccine was not effective in reducing the cumulative incidence of IBK or increasing weaning weight in beef calves.

A systematic review and meta-analysis of the antibiotic treatment for infectious bovine keratoconjunctivitis: an update

Infectious bovine keratoconjunctivitis (IBK) is a common and important disease of calves. Without effective vaccines, antibiotic therapy is often implemented to minimize the impact of IBK. This review updates a previously published systematic review regarding comparative efficacy for antibiotic treatments of IBK. Available years of Centre for Biosciences and Agriculture International and MEDLINE databases were searched, including non-English results. Also searched were the American Association of Bovine Practitioners and World Buiatrics Congress conference proceedings from 1996 to 2016, reviews since 2013, reference lists from relevant trials, and U.S. Food and Drug Administration New Animal Drug Application summaries. Eligible studies assessed antibiotic treatment of naturally-occurring IBK in calves randomly allocated to group at the individual level. Outcomes of interest were clinical score, healing time, unhealed ulcer risk, and ulcer surface area. A mixed-effects model comparing active drug with placebo was employed for all outcomes. Heterogeneity was assessed visually and using Cochran's Q-test. Thirteen trials assessing nine treatments were included. Compared with placebo, most antibiotic treatments were effective. There was evidence that the treatment effect differed by day of outcome measurement. Visually, the largest differences were observed 7-14 days post-treatment. These results indicate improved IBK healing with many antibiotics and suggest the need for randomized trials comparing different antibiotic treatments.

Microbial community sequencing analysis of the calf eye microbiota and relationship to infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is an important production limiting disease in cattle. Moraxella bovis has historically been considered the primary causal agent; however, vaccines have not been consistently shown as effective in controlling disease incidence. The purpose of this study was to examine the bacterial community of calf eyes prior to disease onset using high-throughput sequencing of 16S ribosomal RNA and determine if it was associated with IBK occurrence. The study was designed as a case-control nested within a randomized controlled trial (RCT). Eye swabs were collected from all spring-born calves without clinical signs of IBK (t₀ swabs) on a research farm with a previous history of IBK disease outbreaks. At follow-up or weaning, calves were diagnosed as IBK positive or negative. The lag time between enrollment swabs (t₀) and IBK diagnosis ranged from approximately one to three months. Cases were randomly selected from IBK positive calves and controls were selected from IBK negative calves (i.e. calves that did not exhibit clinical signs of IBK throughout the course of the RCT). Analysis of the fold-change differences between cases and controls did not reveal large-scale distinctions in bacterial composition. However, principal component analysis suggested bacterial composition differences between calf management groups, which were based on dam parity. Moraxella was found to be among the top ten most abundant genera in our population; however, the difference in abundance was not significant between the cases and controls. No large-scale differences in the bacterial communities of calves that did or did not develop IBK were observed in our population. Nevertheless, it remains unclear whether the "natural" bacterial population of the calf might ultimately impact disease status. Further study is warranted to examine bacterial taxa that were observed to be significantly more abundant in the cases or controls as potential vaccines/therapeutic targets.

Efficacy of Bdellovibrio bacteriovorus 109J for the treatment of dairy calves with experimentally induced infectious bovine keratoconjunctivitis

OBJECTIVE To determine the efficacy of Bdellovibrio bacteriovorus 109J for the treatment of calves with experimentally induced infectious bovine keratoconjunctivitis (IBK). ANIMALS 12 healthy dairy calves. PROCEDURES For each calf, a grid keratotomy was performed on both eyes immediately before inoculation with Moraxella bovis hemolytic strain Epp63-300 (n = 11 calves) or nonhemolytic strain 12040577 (1 calf). For each calf inoculated with M bovis Epp63-300, the eyes were randomly assigned to receive an artificial tear solution with (treatment group) or without (control group) lyophilized B bacteriovorus 109J. Six doses of the assigned treatment (0.2 mL/eye, topically, q 48 h) were administered to each eye. On nontreatment days, eyes were assessed and corneal swab specimens and tear samples were collected for bacterial culture. Calves were euthanized 12 days after M bovis inoculation. The eyes were harvested for gross and histologic evaluation and bacterial culture. RESULTS The calf inoculated with M bovis 12040577 did not develop corneal ulcers. Of the 22 eyes inoculated with M bovis Epp63-300, 18 developed corneal ulcers consistent with IBK within 48 hours after inoculation; 4 of those eyes developed secondary corneal ulcers that were not consistent with IBK. Corneal ulcer size and severity and the time required for ulcer healing did not differ between the treatment and control groups. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that B bacteriovorus 109J was not effective for the treatment of IBK; however, the experimental model used produced lesions that did not completely mimic naturally occurring IBK.

Large genomic differences between Moraxella bovoculi isolates acquired from the eyes of cattle with infectious bovine keratoconjunctivitis versus the deep nasopharynx of asymptomatic cattle

Moraxella bovoculi is a recently described bacterium that is associated with infectious bovine keratoconjunctivitis (IBK) or “pinkeye” in cattle. In this study, closed circularized genomes were generated for seven M. bovoculi isolates: three that originated from the eyes of clinical IBK bovine cases and four from the deep nasopharynx of asymptomatic cattle. Isolates that originated from the eyes of IBK cases profoundly differed from those that originated from the nasopharynx of asymptomatic cattle in genome structure, gene content and polymorphism diversity and consequently placed into two distinct phylogenetic groups. These results suggest that there are genetically distinct strains of M. bovoculi that may not associate with IBK.

Review: Assessment of completeness of reporting in intervention studies using livestock: an example from pain mitigation interventions in neonatal piglets

Accurate and complete reporting of study methods, results and interpretation are essential components for any scientific process, allowing end-users to evaluate the internal and external validity of a study. When animals are used in research, excellence in reporting is expected as a matter of continued ethical acceptability of animal use in the sciences. Our primary objective was to assess completeness of reporting for a series of studies relevant to mitigation of pain in neonatal piglets undergoing routine management procedures. Our second objective was to illustrate how authors can report the items in the Reporting guidElines For randomized controLled trials for livEstoCk and food safety (REFLECT) statement using examples from the animal welfare science literature. A total of 52 studies from 40 articles were evaluated using a modified REFLECT statement. No single study reported all REFLECT checklist items. Seven studies reported specific objectives with testable hypotheses. Six studies identified primary or secondary outcomes. Randomization and blinding were considered to be partially reported in 21 and 18 studies, respectively. No studies reported the rationale for sample sizes. Several studies failed to report key design features such as units for measurement, means, standard deviations, standard errors for continuous outcomes or comparative characteristics for categorical outcomes expressed as either rates or proportions. In the discipline of animal welfare science, authors, reviewers and editors are encouraged to use available reporting guidelines to ensure that scientific methods and results are adequately described and free of misrepresentations and inaccuracies. Complete and accurate reporting increases the ability to apply the results of studies to the decision-making process and prevent wastage of financial and animal resources.

Pain and sickness behavior associated with corneal lesions in dairy calves

Infectious bovine keratoconjunctivitis (IBK) is a common corneal disease of calves that adversely affects animal welfare by causing pain and weight loss. Identifying behavioral indicators of pain and sickness in calves with IBK is necessary for designing studies that aim to identify effective means of pain mitigation. Consistent with principles of the 3Rs for animal use in research, data from a randomized blinded challenge study was used to identify and describe variation of behaviors that could serve as reliable indicators of pain and sickness in calves with corneal injuries. Behavioral observations were collected from 29 Holstein calves 8 to 12 weeks of age randomly allocated to one of three treatments: (1) corneal scarification only, (2) corneal scarification with inoculation with Moraxella bovoculi and (3) corneal scarification with inoculation with Moraxella bovis. Behavior was continuously observed between time 1230 - 1730 h on day -1 (baseline time period) and day 0 (scarification time period). Corneal scarification and inoculation occurred between 0800 - 1000 h on day 0. Frequency of head-directed behaviors (head shaking, head rubbing, head scratching) and durations of head rubbing, feeding, standing with head lifted, lying with head lifted and sleeping were compared between study days and groups. Following scarification, the frequency of head-directed behavior significantly increased (p = 0.0001), as did duration of head rubbing (p=0.02). There was no significant effect of trial, trial day, treatment or treatment-day interaction on other behaviors studied. Our study demonstrated that head-directed behavior, such as head shaking, rubbing and scratching, was associated with scarification of eyes using an IBK challenge model, but sickness behavior was not observed.

Moraxella spp. isolated from field outbreaks of infectious bovine keratoconjunctivitis: a retrospective study of case submissions from 2010 to 2013

Infectious bovine keratoconjunctivitis (IBK), also known as pinkeye, is the most costly eye disease of cattle. The principal etiologic agent of IBK is the Gram-negative bacterium Moraxella bovis. However, there have been reports of IBK outbreaks associated with Moraxella bovoculi. A retrospective study of IBK diagnostic cases submitted from July 1, 2010 through October 31, 2013 was conducted. Included in the study were 1,042 Moraxella isolates from 1,538 swabs of lacrimal secretions collected from 282 herds from 30 U.S. states. Moraxella isolates were identified to the species level and were composed of M. bovoculi (701 isolates), M. bovis (295 isolates), Moraxella ovis (5 isolates), and other Moraxella spp. (41). Minimum inhibitory concentrations required for 90% growth inhibition (MIC90) was calculated for representative isolates. The MIC90 values for both M. bovis and M. bovoculi were as follows: ampicillin and ceftiofur: ≤0.25 µg/ml; clindamycin: 2 µg/ml; danofloxacin and enrofloxacin: ≤0.12 µg/ml; florfenicol: 0.5 µg/ml; gentamicin: 1 µg/ml; neomycin: 4 µg/ml; tulathromycin: 2 µg/ml; and tylosin: 8 µg/ml. The MIC90 values for M. bovoculi included the following: chlortetracycline: ≤0.5 µg/ml; oxytetracycline: 4 µg/ml; penicillin: 0.25 µg/ml; spectinomycin: 32 µg/ml; sulfadimethoxine: >256 µg/ml; tiamulin: 1 µg/ml; and trimethoprim-sulfamethoxazole: 4 µg/ml. For M. bovis, MIC90 values included the following: chlortetracycline and oxytetracycline: 1 µg/ml; penicillin: ≤0.12 µg/ml; spectinomycin: 16 µg/ml; sulfadimethoxine: ≤256 µg/ml; tiamulin: ≤0.5 µg/ml; and trimethoprim-sulfamethoxazole: ≤2 µg/ml. The current work describes the frequency of isolation and differences in antimicrobial sensitivity observed among Moraxella isolates from case submissions.

Evaluating approaches to measuring ocular pain in bovine calves with corneal scarification and infectious bovine keratoconjunctivitis-associated corneal ulcerations

Infectious bovine keratoconjunctivitis (IBK) is a common ocular disease in cattle, associated with a 6.8 to 13.6 kg decrease in weaning weight. Antibiotic therapy is available but it is unclear if pain mitigation as an adjunct therapy would reduce the weight loss associated with IBK. Before assessing the impact of pain mitigation therapies, it is first necessary to validate approaches to qualifying ocular pain. The objective of this study was to evaluate approaches to qualifying ocular pain in bovine calves (Bos taurus) with IBK. Our a priori assumption was that scarification or corneal ulcerations consistent with IBK are painful compared to normal eyes. To quantify this difference in pain, we assessed 4 tools: pressure algometry-mechanical nociceptive threshold (PA-MNT), corneal touch thresholds (CTT) obtained with the use of a Cochet-Bonnet aesthesiometer, and assessment for the presence of blepharospasm and photophobia as metrics for pain. Using a 1-eye randomized controlled challenge trial, 31 calves with healthy eyes were randomly allocated to treatment groups, and then a left or right eye was randomly assigned for corneal scarification and inoculation with Moraxella bovoculi or Moraxella bovis. A repeated measures analysis of variance was used for PA-MNT, with significance set at P < 0.05. A log (base 10) transformation was used to stabilize the variance, and Tukey's t tests were used to test differences between assessment days for each landmark. Calves had statistically significantly lower PA-MNT scores (which indicates more pain) the day after scarification relative to baseline measurements (4 d before scarification). For example, at 1 landmark the median PA-MNT (kg/force) prescarification was 4.82 (95% confidence interval [CI]: 3.92-5.93) and 3.43 (95% CI: 2.79-4.22) postscarification. These data suggest PA-MNT may be a tool for quantifying ocular pain in calves. No differences (P < 0.1) in PA-MNT scores between scarified and not-scarified eyes were detected for any landmark on any day. This result suggests that the pain response occurs over the entire face, not just the affected eye. Corneal ulcerations consistent with IBK were not associated with statistically significant differences in PA-MNT or CTT at eye or calf levels. Not surprisingly, scarified eyes were more likely to exhibit blepharospasm and photophobia compared to healthy eyes. Due to blepharospasm, the use of the Cochet-Bonnet to evaluate corneal sensitivity by CTT was of limited value.

The legal foundation of the production and use of herd-specific vaccines in Europe

In veterinary medicine, herd-specific vaccines are primarily used in farm animals if traditional vaccines are either unavailable or do not perform as expected. As autogenous products, these vaccines are exempt from Directive 2001/82/EC, and therefore the production and use of herd-specific vaccines are regulated differently in each member state of the European Union (EU). This study is an overview of the diverse legal statuses of herd-specific vaccines among European countries. The study was conducted by analyzing legal documents, tailored questionnaires answered by subject-related authorities from sixteen European countries, and related literature. These analyses revealed that tremendous heterogeneity exists with respect to the legal requirements for the production and use of herd-specific vaccines among the countries that were examined. In particular, certain countries have detailed and precise regulations for these vaccines, whereas the legislation regarding these vaccines is vague or even nonexistent in other nations. The implementation of standardized definitions, guidelines for vaccine use in the field, and regulations for vaccine production are essential prerequisites for achieving legal consistency across Europe. These measures would also help countries enact pertinent national legislation with less divergence regarding the production and use of herd-specific vaccines and ensure the existence of comparable safety and quality standards for these vaccines among European countries.

Randomized blinded challenge study to assess association between Moraxella bovoculi and Infectious Bovine Keratoconjunctivitis in dairy calves

The objective of this study was to evaluate if Moraxella bovoculi was associated with Infectious Bovine Keratoconjunctivitis (IBK) using a corneal scarification model in calves. A 3-arm single-eye block-randomized and blinded challenge study was designed as follows: corneal scarification only, corneal scarification and inoculation with M. bovoculi (ATCC strain: BAA-1259; origin: CA) and corneal scarification and inoculation with Moraxella bovis (strain Epp63-300; origin: NADC). The study was conducted in 3 replicates of 10-12 animals housed in individual pens with no nose-to-nose contact. Calves were enrolled after an ophthalmologist confirmed the absence of corneal, conjunctival, and eyelid abnormalities. Calves were scarified and inoculated in one randomly selected eye, then observed for the primary outcome of interest (corneal ulcers) until euthanized 10 days following scarification. Research group members assessing the outcome were blind to allocation status. The study was approved by the institutional animal care and use committee. Of 36 animals purchased for the study, 5 were excluded prior to enrollment due to ophthalmic abnormalities. Of the 31 enrolled calves, 9/10 (90%) of M. bovis calves, 0/10 (0%) of M. bovoculi calves and 1/11 (9%) of control calves developed corneal ulcerations consistent with IBK in the scarified eyes. The absence of corneal ulcerations in M. bovoculi BAA-1259 inoculated calves suggests it is not a causal organism for IBK in this model and the pathogenicity of this ATCC strain has not been established. Consistent corneal ulceration development in the M. bovis inoculated group demonstrates the ability of the model to induce IBK ulcers.

Minimum inhibitory concentrations of selected antimicrobial agents for Moraxella bovoculi associated with infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) has been associated with ocular infections by Moraxella bovis, the established etiologic agent of IBK, and more recently, Moraxella bovoculi, a recently described species of Moraxella. To assist in designing rational treatment regimens for M. bovoculi infections associated with IBK, the in vitro susceptibilities of 57 M. bovoculi field isolates cultured from eyes of cattle with IBK in California from 2002 through 2007 were determined. The minimum inhibitory concentration required to inhibit the growth of 90% of organisms (MIC(90)) of the following 18 antibiotics tested in the present study were: danofloxacin and enrofloxacin: ≤0.12 µg/ml; ampicillin and ceftiofur: ≤0.25 µg/ml; penicillin: 0.25 µg/ml; gentamicin: ≤1 µg/ml; chlortetracycline, oxytetracycline, and tiamulin: 1 µg/ml; florfenicol: 0.5 µg/ml; trimethoprim-sulfamethoxazole: ≤2/38 µg/ml; clindamycin: 2 µg/ml; neomycin and tilmicosin: ≤4 µg/ml; tulathromycin: 4 µg/ml; spectinomycin and tylosin: 16 µg/ml; and sulfadimethoxine: >256 µg/ml. The low MIC(90) of these M. bovoculi isolates suggests that commonly used antibiotics for treatment of IBK associated with M. bovis should also be effective against M. bovoculi.

Recombinant Moraxella bovoculi 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.

The REFLECT statement: reporting guidelines for randomized controlled trials in livestock and food safety: explanation and elaboration

Concerns about the completeness and accuracy of reporting of randomized clinical trials (RCTs) and the impact of poor reporting on decision-making have been documented in the medical field over the past several decades. Experience from RCTs in human medicine would suggest that failure to report critical trial features can be associated with biased estimated effect measures, and there is evidence to suggest similar biases occur in RCTs conducted in livestock populations. In response to these concerns, standardized guidelines for reporting RCTs were developed and implemented in human medicine. The Consolidated Standards of Reporting Trials (CONSORT) statement was first published in 1996 with a revised edition published in 2001. The CONSORT statement consists of a 22-item checklist for reporting a RCT and a flow diagram to follow the number of participants at each stage of a trial. An explanation and elaboration document not only defines and discusses the importance of each of the items, but also provides examples of how this information could be supplied in a publication. Differences between human and livestock populations necessitate modifications to the CONSORT statement to maximize its usefulness for RCTs involving livestock. These have been addressed in an extension of the CONSORT statement titled the REFLECT statement: Methods and processes of creating reporting guidelines for randomized control trials for livestock and food safety. The modifications made for livestock trials specifically addressed the common use of group housing and group allocation to intervention in livestock studies, the use of a deliberate challenge model in some trials, and common use of non-clinical outcomes, such as contamination with a foodborne pathogen. In addition, the REFLECT statement for RCTs in livestock populations proposed specific terms or further clarified terms as they pertained to livestock studies.