Infectious bovine keratoconjunctivitis: a review

Supplementing a Bacillus-based probiotic to high-risk stocker cattle

This experiment evaluated the performance, health, and physiological responses of high-risk steers receiving a Bacillus-based probiotic during a 90-d grazing period. A total of 240 Angus-influenced steers were used in this experiment that was replicated over 2 yr (120 steers/year). Each year, steers were obtained from an auction yard and transported to the experimental facility (120 km). Steer body weight (BW) was recorded at arrival (day -1), and this value was averaged with BW recorded on day 0 to represent the initial BW (236.6 ± 1.5 kg). On day 0, steers were ranked by BW and allocated to 1 of 12 pastures with stockpiled native grass (4-ha pastures; 10 steers/pasture). Pastures were randomly assigned to receive daily supplementation with dried distillers' grains at 1% of BW containing either: 1) Bacillus subtilis + B. licheniformis probiotic (BOV; 2 g/steer daily of Bovacillus; Novonesis, Horsholm, Denmark) or 2) no feed additive (CON). Cattle received treatments from days 0 to 90, in addition to free-choice access to water and mineral + vitamin mix without ionophore. Steers were assessed for bovine respiratory disease (BRD) signs daily. Blood samples were collected and full BW was recorded on days 0, 14, 28, 56, and 90. Shrunk BW was recorded on day 91 after 16 h of feed and water restriction, and a 4% pencil shrink was used to calculate the final BW. Average daily gain (ADG) was calculated based on initial and final BW. No treatment effects were detected (P ≥ 0.73) for steer final BW and ADG. A treatment × day interaction was detected (P ≤ 0.05) for plasma haptoglobin concentration, which was greater for CON steers on days 14 and 28 (P ≤ 0.02). Incidence of BRD signs did not differ (P = 0.97) between treatments (51.7% and 51.3% for BOV and CON, respectively; SEM = 7.70). However, steer mortality + removals for health complications were greater (P = 0.01) in CON compared to BOV (0.00% vs. 5.04%, respectively; SEM = 1.41). Supplementing BOV improved (P ≤ 0.04) total pasture-based liveweight change (643 vs. 502 kg/pasture, respectively; SEM = 45) and final pasture-based total liveweight (3,007 vs. 2,869 kg/pasture, respectively; SEM = 46). Collectively, supplementation with a probiotic based on B. subtilis and B. licheniformis to high-risk stocker cattle did not alleviate the incidence of BRD signs nor improved ADG, but decreased acute-phase protein response, reduced steer mortality + removal, and increased pasture-based productivity during a 90-d grazing period.

Alterations to the bovine bacterial ocular surface microbiome in the context of infectious bovine keratoconjunctivitis

BACKGROUND

Infectious bovine keratoconjunctivitis (IBK) is a common cause of morbidity in cattle, resulting in significant economic losses. This study aimed to characterize the bovine bacterial ocular surface microbiome (OSM) through conjunctival swab samples from Normal eyes and eyes with naturally acquired, active IBK across populations of cattle using a three-part approach, including bacterial culture, relative abundance (RA, 16 S rRNA gene sequencing), and semi-quantitative random forest modeling (real-time polymerase chain reaction (RT-PCR)).

RESULTS

Conjunctival swab samples were obtained from eyes individually classified as Normal (n = 376) or IBK (n = 228) based on clinical signs. Cattle unaffected by IBK and the unaffected eye in cattle with contralateral IBK were used to obtain Normal eye samples. Moraxella bovis was cultured from similar proportions of IBK (7/228, 3.07%) and Normal eyes (1/159, 0.63%) (p = 0.1481). Moraxella bovoculi was cultured more frequently (p < 0.0001) in IBK (59/228, 25.88%) than Normal (7/159, 4.40%) eyes. RA (via 16 S rRNA gene sequencing) of Actinobacteriota was significantly higher in Normal eyes (p = 0.0045). Corynebacterium variabile and Corynebacterium stationis (Actinobacteriota) were detected at significantly higher RA (p = 0.0008, p = 0.0025 respectively) in Normal eyes. Rothia nasimurium (Actinobacteriota) was detected at significantly higher RA in IBK eyes (p < 0.0001). Alpha-diversity index was not significantly different between IBK and Normal eyes (p > 0.05). Alpha-diversity indices for geographic location (p < 0.001), age (p < 0.0001), sex (p < 0.05) and breed (p < 0.01) and beta-diversity indices for geographic location (p < 0.001), disease status (p < 0.01), age (p < 0.001), sex (p < 0.001) and breed (p < 0.001) were significantly different between groups. Modeling of RT-PCR values reliably categorized the microbiome of IBK and Normal eyes; primers for Moraxella bovoculi, Moraxella bovis, and Staphylococcus spp. were consistently the most significant canonical variables in these models.

CONCLUSIONS

The results provide further evidence that multiple elements of the bovine bacterial OSM are altered in the context of IBK, indicating the involvement of a variety of bacteria in addition to Moraxella bovis, including Moraxella bovoculi and R. nasimurium, among others. Actinobacteriota RA is altered in IBK, providing possible opportunities for novel therapeutic interventions. While RT-PCR modeling provided limited further support for the involvement of Moraxella bovis in IBK, this was not overtly reflected in culture or RA results. Results also highlight the influence of geographic location and breed type (dairy or beef) on the bovine bacterial OSM. RT-PCR modeling reliably categorized samples as IBK or Normal.

Whole-body microbiota of newborn calves and their response to prenatal vitamin and mineral supplementation

Early life microbial colonization and factors affecting colonization patterns are gaining interest due to recent developments suggesting that early life microbiome may play a role in Developmental Origins of Health and Disease. In cattle, limited information exists on the early microbial colonization of anatomical sites involved in bovine health beyond the gastrointestinal tract. Here, we investigated 1) the initial microbial colonization of seven different anatomical locations in newborn calves and 2) whether these early life microbial communities and 3) serum cytokine profiles are influenced by prenatal vitamin and mineral (VTM) supplementation. Samples were collected from the hoof, liver, lung, nasal cavity, eye, rumen (tissue and fluid), and vagina of beef calves that were born from dams that either received or did not receive VTM supplementation throughout gestation (n = 7/group). Calves were separated from dams immediately after birth and fed commercial colostrum and milk replacer until euthanasia at 30 h post-initial colostrum feeding. The microbiota of all samples was assessed using 16S rRNA gene sequencing and qPCR. Calf serum was subjected to multiplex quantification of 15 bovine cytokines and chemokines. Our results indicated that the hoof, eye, liver, lung, nasal cavity, and vagina of newborn calves were colonized by site-specific microbiota, whose community structure differed from the ruminal-associated communities (0.64 ≥ R² ≥ 0.12, p ≤ 0.003). The ruminal fluid microbial community was the only one that differed by treatment (p < 0.01). However, differences (p < 0.05) by treatment were detected in microbial richness (vagina); diversity (ruminal tissue, fluid, and eye); composition at the phylum and genus level (ruminal tissue, fluid, and vagina); and in total bacterial abundance (eye and vagina). From serum cytokines evaluated, concentration of chemokine IP-10 was greater (p = 0.02) in VTM calves compared to control calves. Overall, our results suggest that upon birth, the whole-body of newborn calves are colonized by relatively rich, diverse, and site-specific bacterial communities. Noticeable differences were observed in ruminal, vaginal, and ocular microbiota of newborn calves in response to prenatal VTM supplementation. These findings can derive future hypotheses regarding the initial microbial colonization of different body sites, and on maternal micronutrient consumption as a factor that may influence early life microbial colonization.

Automated monitoring and detection of disease using a generic facial feature scoring system - A case study on FMD infected cows

Digital images are becoming more readily available and possibilities for image processing are developing rapidly. This opens the possibility to use digital images to monitor and detect diseases in animals. In this paper we present 1) a generic facial feature scoring system based on seven facial features, 2) manual scores of images of Holstein Frisian heifers during foot-and-mouth disease vaccine efficacy trials and 3) automatic disease scores of the same animals. The automatic scoring system was based on the manual version and trained on annotated images from the manual scoring system. For both systems we found an increase in disease scores three days post infection, followed by a recovery. This temporal pattern matched with observations made by animal caretakers. Importantly, the automatic system was able to discern animals that were protected by the vaccine, and did not develop blisters at the feet, and animals that were not protected. Finally, automatic scores could be used to detect healthy and sick animals with a sensitivity and specificity of 0.94 on the second and third days following infection in an experimental setting. This generic facial feature disease scoring system could be further developed and extended to lactating Holstein Frisian dairy cows, other breeds and other infectious diseases. The system could be applied during animal experiments or, after further development, in a farm setting.

Cytological and microbiological evaluation of conjunctiva in camels with and without conjunctivitis

OBJECTIVE

To describe the cytological analysis of conjunctiva from normal camels and camels with bacterial conjunctivitis.

ANIMALS STUDIED

This study was conducted on 7 normal camels and 15 camels affected with conjunctivitis. The affected camels had a history of conjunctivitis with signs including chemosis, blepharospasm, frequent blinking, and mild-to-moderate serous, mucoid, or purulent ocular discharge.

PROCEDURES

Bacterial swabs were collected from the inferior conjunctival sac of the affected eye without topical anesthetics. Conjunctival smears were obtained from the conjunctival surface for cytological analysis.

RESULTS

The cellular analysis of ocular smears revealed a higher percentage of basal cells, neutrophils, eosinophils, and macrophages in camels with conjunctivitis compared with normal camels. In contrast to this, smears from normal camels showed an increased percentage of superficial epithelial cells compared with affected camels. The microbiological assessment of conjunctival swabs collected from affected animals identified a bacterial growth of Staphylococcus aureus., Bacillus sp., Streptococcus sp., Enterococcus faecium., Staphylococcus sp., Corynebacterium sp., Coryne pseudotuberculosis., Saprophytica, Enterobacter cloacae, Escherichia coli, Proteus mirabilis, Proteus vulagaris, and Pseudomonas aeruginosa.

CONCLUSIONS

It was observed that bacterial conjunctivitis in camels was associated with increased percentages of basal epithelial cells, neutrophils, eosinophils, and macrophages compared with normal camels, while normal camels showed an increased percentage of superficial epithelial cells compared with affected camels.

Immunomodulatory Effects of Macrolides Considering Evidence from Human and Veterinary Medicine

Macrolide antimicrobial agents have been in clinical use for more than 60 years in both human and veterinary medicine. The discovery of the non-antimicrobial properties of macrolides and the effect of immunomodulation of the inflammatory response has benefited patients with chronic airway diseases and impacted morbidity and mortality. This review examines the evidence of antimicrobial and non-antimicrobial properties of macrolides in human and veterinary medicine with a focus toward veterinary macrolides but including important and relevant evidence from the human literature. The complete story for these complex and important molecules is continuing to be written.

Genotype classification of Moraxella bovis using MALDI-TOF MS profiles

Moraxella bovis (M. bovis) is regarded as a causative agent of infectious bovine keratoconjunctivitis (IBK), the most common ocular disease of cattle. Recently, whole genome sequencing identified the presence of two distinct genotypes within M. bovis that differ in chromosome content, potential virulence factors, as well as prophage and plasmid profiles. It is unclear if the genotypes equally associate with IBK or if one is more likely to be isolated from IBK lesions. We utilized 39 strains of M. bovis that had previously undergone whole genome sequencing and genotype classification to determine the utility of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) to accurately genotype M. bovis strains. We successfully developed two biomarker models that accurately classified strains according to genotype with an overall accuracy of 85.8-100% depending upon the model and sample preparation method used. These models provide a practical tool to enable studies of genotype associations with disease, allow for epidemiological studies at the sub-species level, and can be used to enhance disease prevention strategies.

Investigation of foot and mouth disease virus and other animal pathogens in cattle, buffaloes and goats at the interface with Akagera National Park 2017 - 2020

BACKGROUND

Foot-and-Mouth Disease Virus (FMDV) is a positive-sense RNA virus of the family of the picornaviridæ that is responsible for one of the livestock diseases with the highest economic impact, the Foot-and-Mouth Disease (FMD). FMD is endemic in Rwanda but there are gaps in knowing its seroprevalence and molecular epidemiology. This study reports the FMD seroprevalence and molecular characterization of FMDV in Eastern Rwanda.

RESULTS

The overall seroprevalence of FMD in the study area is at 9.36% in cattle and 2.65% in goats. We detected FMDV using molecular diagnostic tools such as RT-PCR and RT-LAMP and the phylogenetic analysis of the obtained sequences revealed the presence of FMDV serotype SAT 2, lineage II. Sequencing of the oropharyngeal fluid samples collected from African buffaloes revealed the presence of Prevotela ruminicola, Spathidium amphoriforme, Moraxella bovoculi Onchocerca flexuosa, Eudiplodinium moggii, Metadinium medium and Verrucomicrobia bacterium among other pathogens but no FMDV was detected in African buffaloes.

CONCLUSIONS

We recommend further studies to focus on sampling more African buffaloes since the number sampled was statistically insignificant to conclusively exclude the presence or absence of FMDV in Eastern Rwanda buffaloes. The use of RT-PCR alongside RT-LAMP demonstrates that the latter can be adopted in endemic areas such as Rwanda to fill in the gaps in terms of molecular diagnostics. The identification of lineage II of SAT 2 in Rwanda for the first time shows that the categorised FMDV pools as previously established are not static over time.

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).

Antimicrobial efficacy of in vitro and ex vivo photodynamic therapy using porphyrins against Moraxella spp. isolated from bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is an ocular disease affecting bovine herds worldwide, and it causes significant economic loss. The etiologic agent of IBK is considered to be Moraxella bovis, but M. ovis and M. bovoculi are frequently recovered of animals presenting clinical signs of IBK. The therapeutic measures available for its control have limited efficacy. Antimicrobial photodynamic therapy (aPDT) using porphyrins as photosensitizing molecules is an alternative method that can be used to reduce microbial growth. We evaluated the antibacterial activity of aPDT using two water-soluble tetra-cationic porphyrins (H₂TMeP and ZnTMeP) against 22 clinical isolates and standard strains of Moraxella spp. in vitro and in an ex vivo model. For the in vitro assay, 4.0 µM of porphyrin was incubated with approximately 1.0 × 10⁴ CFU/mL of each Moraxella sp. isolate and exposed to artificial light for 0, 2.5, 5, and 7.5 min. Next, 50 µL of this solution was plated and incubated for 24 h until CFU measurement. For the ex vivo assay, corneas excised from the eyeballs of slaughtered cattle were irrigated with Moraxella spp. culture, followed by the addition of zinc(II) porphyrin ZnTMeP (4.0 μM). The corneal samples were irradiated for 0, 7.5, and 30 min, followed by swab collection, plating, and CFU count. The results demonstrated the in vitro inactivation of the strains and clinical isolates of Moraxella spp. after 2.5 min of irradiation using ZnTMeP, reaching complete inactivation until 7.5 min. In the ex vivo experiment, the use of ZnTMeP resulted in the most significant reduction in bacterial concentration after 30 min of irradiation. These results encourage future in vivo experiments to investigate the role of metalloporphyrin ZnTMeP in the inactivation of Moraxella spp. isolates causing IBK.

Assessment of Cidofovir for Treatment of Ocular Bovine Herpesvirus-1 Infection in Cattle Using an Ex-Vivo Model

Bovine herpesvirus-1 (BoHV-1) infection contributes to keratoconjunctivitis, respiratory disease, and reproductive losses in cattle. The objective of this study was to determine the most appropriate ophthalmic antiviral agent for BoHV-1 inhibition using in-vitro culture and novel ex-vivo bovine corneal modeling. Half-maximal inhibitory concentrations of BoHV-1 were determined for cidofovir, ganciclovir, idoxuridine, and trifluridine via in-vitro plaque reduction assays. In-vitro cytotoxicity was compared amongst these compounds via luciferase assays. Trifluridine and cidofovir were the most potent BoHV-1 inhibitors in vitro, while trifluridine and idoxuridine were the most cytotoxic agents. Therefore, cidofovir was the most potent non-cytotoxic agent and was employed in the ex-vivo corneal assay. Corneoscleral rings (n = 36) from fresh cadaver bovine globes were harvested and equally divided into an uninfected, untreated control group; a BoHV-1-infected, untreated group; and a BoHV-1-infected, cidofovir-treated group. Virus isolation for BoHV-1 titers was performed from corneal tissue and liquid media. Histologic measurements of corneal thickness, epithelial cell density, and tissue organization were compared between groups. Substantial BoHV-1 replication was observed in infected, untreated corneas, but BoHV-1 titer was significantly reduced in cidofovir-treated (1.69 ± 0.08 × 10³ PFU/mL) versus untreated (8.25 ± 0.25 × 10⁵ PFU/mL, p < 0.0001) tissues by day 2 of culture. No significant differences in histologic criteria were observed between groups. In conclusion, cidofovir warrants further investigation as treatment for BoHV-1 keratoconjunctivitis, with future studies needed to assess in-vivo tolerability and efficacy.

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 Role of Environmental Factors in the Epidemiology of Infectious Bovine Keratoconjunctivitis

Environmental factors that contribute to the pathogenesis of infectious bovine keratoconjunctivitis (IBK) include face flies, ultraviolet (UV) radiation, and mechanical irritation from plant awns or dust. Limited research has shown face fly control to be associated with lower incidence of IBK. UV radiation is known to cause corneal irritation and damage in mammalian species. The increased formation of corneal dark cells has been observed following UV radiation in exposed calves. Moraxella bovis preferentially binds to corneal dark cells where it can be found in pits, which may be formed due to bacterial contact. Little is known about the efficacy of management of pasture plants on the prevention of IBK.

Defining and Diagnosing Infectious Bovine Keratoconjunctivitis

Pinkeye and infectious bovine keratoconjunctivitis (IBK) are imprecise terms that describe diverse ocular diseases. Moraxella bovis is the major causative agent of IBK; however, disease epidemiology is not fully known. Not all cases referred to as pinkeye are of infectious origin, and not all IBK involve M bovis. This article suggests the term pinkeye should no longer be used, offers a case definition for IBK (a herd disease), and suggests describing ocular signs of IBK using existing clinical descriptors rather than resorting to novel scores. A new term "ocular moraxellosis" is defined as IBK from which Moraxella spp are demonstrated.

A Review of Global Prevalence and Economic Impacts of Infectious Bovine Keratoconjunctivitis

A summary of available literature on the prevalence and estimated economic impacts of infectious bovine keratoconjunctivitis (IBK) from around the world is made. Country-level prevalence of IBK has been reported only for the United States, Australia, and New Zealand. We provide an estimate of IBK prevalence rate by geographic climate and region accounting for cattle sub-species and age. Estimated prevalence worldwide is 2.78%. Historical economic impact assessments are available only for the United States, Australia, and United Kingdom. Rarely do assessments capture the full economic cost of the disease. Better data on prevalence and how treatment and prevention decisions modify disease impacts is required to estimate the global economic impact.

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.

Future Directions for Research in Infectious Bovine Keratoconjunctivitis

In this article, the authors summarize the future needs from a research perspective to make the greatest gains. They discuss the areas of research: diagnosis, epidemiology, economic impact, prevention, and treatment. In some areas, simple studies with little cost could be conducted that would quickly add to the evidence base. In other areas, substantial investment is needed if new study approaches, which do not repeat past studies' failures, are to be conducted. To maximize the value of research funding, it is essential to critically evaluate the information gains from prior studies and ensure that studies increase knowledge incrementally.

The epizootic situation of cattle moraxellosis in several economic entities of the Republic of Kazakhstan

BACKGROUND AND AIM

Infectious bovine keratoconjunctivitis (IBK; conjunctivitis) is a widespread eye disease in cattle. In 1960, the Gram-negative bacillus Moraxella bovis was discovered as one of IBK's etiological causal agents. This study aimed to clarify the epidemiological (epizootic) situation of cattle moraxellosis in the Republic of Kazakhstan. The study also maps the quantitative and qualitative indicators of the epidemiological (epizootic) process to develop more effective antiepizootic measures.

MATERIALS AND METHODS

We clinically examined both imported and local cattle species based on existing epidemiological (epizootological) units of economic entities in Kazakhstan. Then, we selected biomaterials for laboratory tests to screen for moraxellosis.

RESULTS

We clarified the epizootic situation for moraxellosis of cattle in Kazakhstan using data from the Meat Union of Kazakhstan, veterinary reports from the Veterinary Control and Surveillance Committee of the Ministry of Agriculture, Kazakhstan, and our results, obtained during visits to farms in the various regions of the republic.

CONCLUSION

Based on the data of the conducted studies, we developed epizootic visualization maps with quantitative indicators of the cattle moraxellosis epizootic-transfer processes within various regions of Kazakhstan for 2019. The data obtained from studies of the properties of the isolated cultures compared with the characteristics of reference strains gave grounds to classify them as belonging to the Moraxella genus.

MALDI-TOF MS Biomarker Detection Models to Distinguish RTX Toxin Phenotypes of Moraxella bovoculi Strains Are Enhanced Using Calcium Chloride Supplemented Agar

Moraxella bovoculi is the bacterium most often cultured from ocular lesions of cattle with infectious bovine keratoconjunctivitis, also known as bovine pinkeye. Some strains of M. bovoculi contain operons encoding for a repeats-in-toxin (RTX) toxin, which is a known virulence factor of multiple veterinary pathogens. We explored the utility of MALDI-TOF MS and biomarker detection models to classify the presence or absence of an RTX phenotype in M. bovoculi. Ninety strains that had undergone whole genome sequencing were classified by the presence or absence of complete RTX operons and confirmed with a visual assessment of hemolysis on blood agar. Strains were grown on Tryptic Soy Agar (TSA) with 5% sheep blood, TSA with 5% bovine blood that was supplemented with 10% fetal bovine serum, 10 mmol/LCaCl₂, or both. The formulations were designed to determine the influence of growth media on toxin production or activity, as calcium ions are required for toxin secretion and activity. Mass spectra were obtained for strains grown on each agar formulation and biomarker models were developed using ClinProTools 3.0 software. The most accurate model was developed using spectra from strains grown on TSA with 5% bovine blood and supplemented with CaCl₂, which had a sensitivity and specificity of 93.3% and 73.3%, respectively, regarding RTX phenotype classification. The same biomarker model algorithm developed from strains grown on TSA with 5% sheep blood had a substantially lower sensitivity and specificity of 68.0% and 52.0%, respectively. Our results indicate that MALDI-TOF MS biomarker models can accurately classify strains of M. bovoculi regarding the presence or absence of RTX toxin operons and that agar media modifications improve the accuracy of these models.

Cloxacillin nanostructured formulation for the treatment of bovine keratoconjunctivitis

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Infectious bovine keratoconjunctivitis (IBK) is a widespread, contagious ocular disease that affects especially dairy breeds.

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The mucoadhesive nanoparticle promoted a greater ability of adherence of cloxacillin benzathine to the ocular surface.

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The mucoadhesive nanoparticle-based formulation promoted clinical cure with a low number of doses of antibiotics.

Infectious bovine keratoconjunctivitis (IBK) is a widespread, contagious ocular disease that affects cattle, especially dairy breeds. The disease is caused by Gram-negative bacteria mainly Moraxella bovis, and its treatment consists of parenteral or topic antibiotic therapy. The topic treatment approach is used more commonly in lactating cows, to avoid milk disposal. However, treatment failures are common, because the antibiotic is removed during lacrimation. This study aimed to evaluate the susceptibility of commercial cloxacillin and evaluate the efficacy of nanostructured cloxacillin in clinical cases of IBK by Moraxella. The minimum inhibitory concentration (MIC) of nanoparticle cloxacillin nanocoated, the nanoparticle without the antibiotic and the commercial cloxacillin were determined in vitro with field samples of Moraxella ovis (5) and Moraxella bovis (5). The efficiency of nanoparticles was tested in three cows naturally infected that were treated with 1.0 mL (with 0.32 mg of nanostructured cloxacillin) for the ocular route. Moraxella bovis was isolated and identified by biochemical and molecular methods before the treatment. The animals were treated every 12 h for six days. The cure was considered by the absence of clinical symptoms and bacteria after treatment. The mucoadhesive nanoparticle-based formulation promoted clinical cure with a low number of doses of antibiotics, probably due to the maintenance of the MIC in the ocular mucosa for longer due to the mucoadhesive characteristics of the nanoparticle. The results indicate that the use of nanocoated cloxacillin is possible to control infectious bovine keratoconjunctivitis.

Genetic differences among Moraxella bovis and Moraxella bovoculi isolates from infectious bovine keratoconjunctivitis (IBK) outbreaks in southern Brazil

The objective of this study was to evaluate the genetic diversity of Moraxella bovis and Moraxella bovoculi bacteria isolated from infectious bovine keratoconjunctivitis (IBK) outbreaks in the state of Rio Grande do Sul, Brazil. The genetic diversity among Moraxella spp. was evaluated by RAPD-PCR, JWP1-JWOPA07-PCR, ERIC-PCR and by sequencing the 16S-23S intergenic regions. Based on the dendrogram, two genetically differentiated clades were observed; 14 isolates were classified as M. bovis and 17 as M. bovoculi. Genetic distances between the M. bovis samples ranged from 0.0379 to 0.4285, while for M. bovoculi the dissimilarities ranged from zero to 0.7297. Alternatively, based on sequencing analyses of the 16S-23S intergenic region, M. bovis and M. bovoculi isolates were grouped into the same two different clades, but it was not possible to differentiate between isolates within clades. PCR techniques were demonstrated to be a satisfactory tool to unravel the genetic variability among Moraxella spp., while sequencing of the 16S-23S intergenic region was only able to differentiate two species of the Moraxella genus. Despite sampling geographically close regions, we demonstrate considerable genetic diversity in M. bovis and M. bovoculi strains and genetically distinct M. bovis strains co-infecting the same animal.

Rapid differentiation of Moraxella bovoculi genotypes 1 and 2 using MALDI-TOF mass spectrometry profiles

Moraxella bovoculi is the most frequently isolated bacteria from the eyes of cattle with Infectious Bovine Keratoconjunctivitis (IBK), also known as bovine pinkeye. Two distinct genotypes of M. bovoculi, genotype 1 and genotype 2, were characterized after whole genome sequencing showed a large degree of single nucleotide polymorphism (SNP) diversity within the species. To date, both genotypes have been isolated from the eyes of cattle without clinical signs of IBK while only genotype 1 strains have been isolated from the eyes of cattle with clinical signs of IBK. We used 38 known genotype 1 strains and 26 known genotype 2 strains to assess the ability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to accurately genotype M. bovoculi strains using mass spectrum biomarkers. Mass spectrum data was analyzed with ClinProTools 3.0 software and six models were developed that classify strain genotypes with accuracies ranging from 90.6% - 100%. Finally, using four of the most genotype-specific peaks that also exhibited high peak intensities from the six automated models, we developed a customized model (UNL assisted model) that had recognition capability, validation, and classification accuracies of 100% for genotype classification. Our results indicate that MALDI-TOF MS biomarkers can be used to accurately discriminate genotypes of M. bovoculi without the need for additional methods.

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.

Complete Genome Sequence of Moraxella bovis Strain Epp-63 (300), an Etiologic Agent of Infectious Bovine Keratoconjunctivitis

We report here the complete closed genome sequence of Moraxella bovis strain Epp-63 (300) (Epp63). This strain was isolated from an infectious bovine keratoconjunctivitis (IBK) case in 1963. Since then, Epp63 has been used extensively for IBK research. Consequently, the genome sequence of Epp63 should help elucidate IBK host-pathogen interactions.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of Moraxella bovoculi and Moraxella bovis isolates from cattle

Infectious bovine keratoconjunctivitis (IBK) is an economically significant disease caused by Moraxella bovis. Moraxella bovoculi, although not reported to cause IBK, has been isolated from the eyes of cattle diagnosed with IBK. Identification of M. bovis and M. bovoculi can be performed using biochemical or DNA-based approaches, both of which may be time consuming and inconsistent between laboratories. We conducted a comparative evaluation of M. bovoculi and M. bovis identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with a database provided by Bruker Daltonics (termed the BDAL database), the BDAL database supplemented with spectra generated in our study (termed the UNLVDC database), and with PCR-restriction-fragment length polymorphism (PCR-RFLP) typing. M. bovoculi ( n = 250) and M. bovis ( n = 18) isolates from cattle with or without IBK were used. MALDI-TOF MS using the UNLVDC database correctly identified 250 of 250 (100%) of M. bovoculi and 17 of 18 (94%) of M. bovis isolates. With the BDAL database, MALDI-TOF MS correctly identified 249 of 250 (99%) of M. bovoculi and 7 of 18 (39%) of M. bovis isolates. In comparison, the PCR-RFLP test correctly identified 210 of 250 (84%) of M. bovoculi and 12 of 18 (66%) of M. bovis isolates. Thus, MALDI-TOF MS with the UNLVDC database was the most effective identification methodology for M. bovis and M. bovoculi isolates from cattle.

Antigenic characterization of Moraxella bovis, Moraxella bovoculi and Moraxella ovis strains with potential use in vaccines

Moraxella bovis is historically known as the primary agent of infectious bovine keratoconjunctivitis (IBK). However, Moraxella bovoculi and Moraxella ovis are also reported to be involved in the pathogenesis of IBK, therefore, these three species should be included in the development of a new vaccine with a broad-spectrum protection against the disease natural challenge. In this study we investigated the antigenic properties of clinical isolates and reference strains of M. bovis, M. bovoculi and M. ovis using a novel in vitro approach for vaccine evaluation based on two techniques, flow cytometry and western blotting (WB). Here, we demonstrated that rabbit antisera produced against reference M. bovis strain and commercial bacterin showed low number of IgG with capacity to recognize a panel of heterologous strains composed by M. bovoculi and M. ovis. On the other hand, the antisera generated against two clinical isolates of M. ovis (Mov2 and Mov3) presented high cross-reactivity levels against all M. ovis and M. bovis strains evaluated. Similarly, the antisera against Mbv3 (clinical isolate of M. bovoculi) had high levels of IgG associated on the surface of all M. bovoculi strains and most of the M. ovis strains analyzed. The WB analysis demonstrated that Moraxella spp. has multiple immunogenic antigens and most of them are shared between the three species. Based on the cross-reactivity analysis and considering the relative number of IgGs associated on the bacterial surface, we suggest that a multivalent vaccine including Mbv3, Mov2 and Mov3 strains may provide a strong and broad protection against all strains involved in IBK outbreaks.

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.

Fungi Isolated From House Flies (Diptera: Muscidae) on Penned Cattle in South Texas

Musca domestica L. were collected from cattle diagnosed with bovine ringworm to evaluate the potential of the house fly to disseminate Trichophyton verrucosum E. Bodin, a fungal dermatophyte that is the causative agent for ringworm in cattle. Fungal isolates were cultured from 45 individual flies on supplemented Sabouraud dextrose agar, and isolates were identified using morphological and microscopic approaches. Each isolate was identified further by PCR amplification of the ribosomal DNA locus with fungal-specific primers and subsequent amplicon sequencing. Trichophyton verrucosum was not identified using these approaches. However, 35 different fungal species representing 17 genera were cultured from collected flies, including several species that are allergenic and pathogenic to humans and animals. Several species within the fungal orders Hypocreales, Microascales, Onygenales, Saccharomycetales, Xylaniales, and Agaricales were observed for the first time on house flies. The most frequent fungus recovered was Cladosporium cladosporoides Fresen, which is known to be a ubiquitous, airborne allergen to humans.

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.

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.

Point prevalence of infection with Mycoplasma bovoculi and Moraxella spp. in cattle at different stages of infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) has significant economic consequences and a detrimental impact on animal welfare. Although Moraxella (Mor.) bovis is the primary causative agent, the role of other bacteria, such as Mor. ovis, Mor. bovoculi and Mycoplasma (Myc.) bovoculi, is not well understood. To assess the prevalence of infection with these organisms, and to correlate this with outbreaks of IBK, conjunctival samples from four herds of cattle in Germany of differing IBK status were examined. Herds were selected to represent a hypothetical course of IBK ranging from the pre-outbreak stage (herd 1), to the acute disease stage (herd 2), to a stage where treatment had ceased (herd 3). Unaffected animals were also included (herd 4). To facilitate effective, sensitive sample analysis, a new real-time PCR for Myc. bovoculi was developed and used in concert with established real-time PCR protocols for Myc. bovis and Moraxella spp. Herds 1 and 2 showed similarly high rates of detection for Myc. bovoculi (92.5% and 84.0%, respectively), whereas herds 3 and 4 had a lower prevalence (35.5% and 26.2%, respectively). Mor. bovis and Mor. ovis were more prevalent in herd 1 (32.5% and 87.5%, respectively) and herd 2 (38% and 58%, respectively) than herd 3 (10.4% and 1.3%, respectively) and herd 4 (9.8% and 31.1%, respectively). Mor. bovoculi was the only pathogen that correlated with clinical signs of IBK; at 20% prevalence, it was almost exclusively detected in herd 2. The results indicate that herds with high Myc. bovoculi prevalence are more predisposed to outbreaks of IBK, possibly due to a synergistic interaction with Moraxella spp.

A Study on the Nature of Association between Demodex Mites and Bacteria Involved in Skin and Meibomian Gland Lesions of Demodectic Mange in Cattle

The nature of association between Demodex mites and bacteria involved in bovine demodectic mange lesions and the normal flora inhabiting the skin of noninfected animals was investigated. Demodex bovis and D. ghanensis mites were isolated from the infected purulent material extracted from skin and meibomian gland lesions, respectively. The mites could not be demonstrated in skin brushings or impression smears from the eyes of noninfected cattle. Pathogenic bacteria (Staphylococcus aureus and Streptococcus pyogenes (Group A)) and opportunistic organisms (Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Trueperella pyogenes) were isolated from skin lesions of demodectic mange, and Moraxella bovis and Staphylococcus aureus were isolated from meibomian gland lesions. Bacillus subtilis, Escherichia coli, Proteus vulgaris, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes (Group A) were isolated from skin brushings from noninfected cattle. The nature of association between Demodex mites and bacteria in demodectic mange lesions is synergistic and of equal significance. Pathogenic and opportunistic bacteria facilitated the establishment of Demodex mites in the lesions produced and provided an excellent microclimate for the mites to propagate and reproduce, resulting in severe and progressive disease. The “high-turnover” granulomatous reaction which characterized the histopathological changes proved that Demodex mites and associated bacteria were persistent and immunogenic.

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.

Type IV pilin proteins: versatile molecular modules

Type IV pili (T4P) are multifunctional protein fibers produced on the surfaces of a wide variety of bacteria and archaea. The major subunit of T4P is the type IV pilin, and structurally related proteins are found as components of the type II secretion (T2S) system, where they are called pseudopilins; of DNA uptake/competence systems in both Gram-negative and Gram-positive species; and of flagella, pili, and sugar-binding systems in the archaea. This broad distribution of a single protein family implies both a common evolutionary origin and a highly adaptable functional plan. The type IV pilin is a remarkably versatile architectural module that has been adopted widely for a variety of functions, including motility, attachment to chemically diverse surfaces, electrical conductance, acquisition of DNA, and secretion of a broad range of structurally distinct protein substrates. In this review, we consider recent advances in this research area, from structural revelations to insights into diversity, posttranslational modifications, regulation, and function.

Genome-wide association study of infectious bovine keratoconjunctivitis in Angus cattle

BACKGROUND

Infectious Bovine Keratoconjunctivitis (IBK) in beef cattle, commonly known as pinkeye, is a bacterial disease caused by Moraxellabovis. IBK is characterized by excessive tearing and ulceration of the cornea. Perforation of the cornea may also occur in severe cases. IBK is considered the most important ocular disease in cattle production, due to the decreased growth performance of infected individuals and its subsequent economic effects. IBK is an economically important, lowly heritable categorical disease trait. Mass selection of unaffected animals has not been successful at reducing disease incidence. Genome-wide studies can determine chromosomal regions associated with IBK susceptibility. The objective of the study was to detect single-nucleotide polymorphism (SNP) markers in linkage disequilibrium (LD) with genetic variants associated with IBK in American Angus cattle.

RESULTS

The proportion of phenotypic variance explained by markers was 0.06 in the whole genome analysis of IBK incidence classified as two, three or nine categories. Whole-genome analysis using any categorisation of (two, three or nine) IBK scores showed that locations on chromosomes 2, 12, 13 and 21 were associated with IBK disease. The genomic locations on chromosomes 13 and 21 overlap with QTLs associated with Bovine spongiform encephalopathy, clinical mastitis or somatic cell count.

CONCLUSIONS

Results of these genome-wide analyses indicated that if the underlying genetic factors confer not only IBK susceptibility but also IBK severity, treating IBK phenotypes as a two-categorical trait can cause information loss in the genome-wide analysis. These results help our overall understanding of the genetics of IBK and have the potential to provide information for future use in breeding schemes.

Ulcerative fungal keratitis in a Brown Swiss cow

An 11-year-old Brown Swiss cow was referred to the Farm Animal Department of the Veterinary Teaching Hospital in Zurich, Switzerland, because of lateral recumbency due to puerperal hemolytic anemia. The animal had developed enophthalmos due to dehydration at the time of presentation. Two days after hospitalization, the cow showed blepharospasm and epiphora of the right eye. Ophthalmic examination of the right eye revealed a fluorescein-positive, paraxial, superficial corneal ulcer with focal edema, and mild superficial neovascularization. White corneal stromal infiltrates were seen at the edges of the ulcer bed. After initial topical treatment with an antibiotic ointment (Neomycin 3.5 mg/g, Bacitracin 250 IU/g) three times a day, an increase in corneal infiltrates was noted on re-examination 2 days later. Several fluorescein-negative, punctate, stromal, white opacities were seen dorsal to the ulcer. Cytology demonstrated the presence of fungal hyphae. Topical treatment with 2% miconazole ointment and 0.36% K-EDTA eye drops six times daily and four times daily, respectively, from the second day and continued antibiotics three times daily resolved the clinical symptoms within 6 days. Fungal culture identified the fungal organism as Eurotium amstelodami.

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.

Surto de ceratoconjuntivite infecciosa bovina e hemoncose causando mortalidade em bezerros

É descrito um surto de ceratoconjuntivite infecciosa bovina (CIB) e hemoncose intercorrente afetando um grupo de 116 bezerros de 1-2 anos de idade na região central do Rio Grande do Sul. Vinte bezerros foram afetados e nove morreram. Os sinais clínicos incluíam perda de peso, marcada palidez da mucosa oral, lacrimejamento, opacidade focal da córnea e avermelhamento da conjuntiva. Sinais mais avançados incluíam lacrimejamento copioso, opacidade da córnea, ceratocone, ceratomalacia e cegueira. O diagnóstico de CIB foi baseado nos achados epidemiológicos e clínico-patológicos e confirmado pela cultura de uma cepa hemolítica de Moraxella bovis dos olhos de dois terneiros afetados. O alto coeficiente de letalidade (45%) neste surto foi atribuído a grave hemoncose intercorrente.

RTX proteins: a highly diverse family secreted by a common mechanism

Repeats-in-toxin (RTX) exoproteins of Gram-negative bacteria form a steadily growing family of proteins with diverse biological functions. Their common feature is the unique mode of export across the bacterial envelope via the type I secretion system and the characteristic, typically nonapeptide, glycine- and aspartate-rich repeats binding Ca²⁺ ions. In this review, we summarize the current state of knowledge on the organization of rtx loci and on the biological and biochemical activities of therein encoded proteins. Applying several types of bioinformatic screens on the steadily growing set of sequenced bacterial genomes, over 1000 RTX family members were detected, with the biological functions of most of them remaining to be characterized. Activities of the so far characterized RTX family members are then discussed and classified according to functional categories, ranging from the historically first characterized pore-forming RTX leukotoxins, through the large multifunctional enzymatic toxins, bacteriocins, nodulation proteins, surface layer proteins, up to secreted hydrolytic enzymes exhibiting metalloprotease or lipase activities of industrial interest.