Isolation of Mycoplasma bovoculi from cases of infectious bovine keratoconjunctivitis.

Five outbreaks of infectious bovine keratoconjunctivitis were examined for bacteria and mycoplasmas. Mycoplasma bovoculi was demonstrated in four of the five outbreaks. Other mycoplasmatales were represented by Ureaplasma in one sample. Moraxella bovis and Neisseria ovis were found in all the outbreaks, the former being present in the vast majority of the animals. Transmission experiments with Mycoplasma bovoculi and Moraxella bovis in combination were carried out on four young, colostrumdeprived calves. Mycoplasma bovoculi appeared to have an enhancing effect on the pathogenicity of Moraxella bovis.     

Procaine penicillin by subconjunctival injection in the treatment of infectious bovine keratoconjunctivitis

A profile off the penicillin concentration in bovine conjunctival sac fluid (CF) was determined after a single subconjunctival injection of procaine penicillin (6 x 10(5) iu in 2ml). When the injection was made through the skin of the upper eye lid, the duration of therapeutic concentration was significantly greater (P<0.01) than when the injection had been given by the perconjunctival route: approximately 68 hours or 40 hours respectively. These findings support the clinical use of subconjunctivally administered procaine penicillin in the treatment of infectious bovine keratoconjunctivitis. A single application of an equivalent dose of either procaine penicillin or benethamine penicillin, applied topically in a simple occulentum base, produced a therapeutic duration in CF of 37 +/- 4 hr and 56 +/- 4.5 hr respectively.     

Efficacy of florfenicol for treatment of naturally occurring infectious bovine keratoconjunctivitis

OBJECTIVE: To determine the efficacy of florfenicol for treatment of calves with naturally occurring infectious bovine keratoconjunctivitis (IBK). DESIGN: Randomized controlled field trial. ANIMALS: 63 beef calves and 80 dairy calves between 4 and 12 months of age. PROCEDURE: Calves were randomly assigned to 1 of 3 treatment groups. Calves in the SC treatment group received a single dose of florfenicol (40 mg/kg [18.2 mg/lb of body weight), SC, on day 0. Calves in the IM treatment group received florfenicol (20 mg/kg [9.1 mg/lb]), IM, on days 0 and 2. Calves in the control group received injections of saline solution (0.9% NaCl), IM, on days 0 and 2. Calves were reevaluated every other day for 20 days after treatment. RESULTS: Corneal ulcers healed by day 20 in 48 of 49 (98%) calves treated with florfenicol IM, 39 of 42 (93%) calves treated with florfenicol SC, and 33 of 52 (63%) control calves. CONCLUSIONS AND CLINICAL RELEVANCE: Florfenicol administered SC (1 dose) or IM (2 doses 48 hours apart) was effective for treatment of calves with naturally occurring IBK.     

Comparison of vaccination and treatment in controlling naturally occurring infectious bovine keratoconjunctivitis.

A vaccination study for infectious bovine keratoconjunctivitis was conducted on 108 newborn Hereford calves in the US Department of Agriculture Meat Animal Research Center cattle herd at Clay Center, Nebraska. Groups were allocated so that age of calf, sex of calf, and age of dam were equally distributed between the 54 vaccinated (group I) and the 54 nonvaccinated (group 2) control calves. The dams of both groups of calves were monitored as group 3 controls. An autogenous Moraxella bovis bacterin (formalin-killed, whole cells) was given IM at birth and at approximate intervals of 2 weeks for a total of 3 doses. Bacterial isolation rates for the cattle in groups 1, 2, and 3 during the summer were 92.6%, 92.6%, and 54.1%, respectively, and disease rates were 100%, 96.3%, and 70.6%. The rates were significantly (P less than 0.05) different between calves and cows. Vaccination of calves at birth permitted serum antibodies to develop before the calves were extensively exposed to infection; however, immunity to the disease did not develop. In a treatment study of other animals in the same herd, but in another pasture, the same criteria were used for allocation of 107 cow-calf pairs. Eye spray was applied to treated principals (group 4, 52 calves; and group 6, 53 cows) each week after examination and sample collection. Controls consisted of 54 calves (group 5) and 54 cows (group 7) that were examined and cultured bacteriologically in the same manner. The bacterial isolation and disease rates were less (P less than 0.05) in the treated calves (group 4) than in the nontreated controls (group 5). The differences in bacterial isolation rates between groups 6 and 7 were not significant, but group 6 had less (P less than 0.05) grade III lesions than did group 7. Weekly treatment appeared to be more effective in reducing the incidence of disease than did vaccination.     

Further data to the aetiology, pathogenesis and therapy of infectious bovine keratoconjunctivitis

Out of a total of 224 bovine eye secretions, 126 Moraxella bovis and 64 Neisseria ovis strains were isolated. The pathogenesis and histological lesions caused by Neisseria ovis have been studied on the eyes of three calves naturally affected with IBK, using electron microscopy.

Neisseria ovis caused in 1–12 weeks old calves acute, transient and mostly benign serous conjunctivitis with only slight affection of the cornea. More rarely erosions and even ulceration of the cornea have been observed.

Moraxella bovis and Neisseria ovis strains proved nearly unanimously sensitive in vitro to chloramphenicol, neomycin, oxytetracyclin, nitrofurantoin, erythromycin and cefoperazone. Other antibiotics and chemotherapeutics inhibited the growth of these agents only partly or were ineffective.

Experimental therapy has been carried out using a single i.m. injection of Terramycin/LA inj. (Pfizer) in a dose of 20 mg/kg body mass, repeated if necessary after 72–96 h. This formulation proved more effective and practical than treatments used earlier.     

Effectiveness of two benzathine cloxacillin formulations for treatment of naturally occurring infectious bovine keratoconjunctivitis

A field study was performed to determine the effectiveness of benzathine cloxacillin for the treatment of infectious bovine keratoconjunctivitis in cattle from 2 farms located in northern California. The study was performed between June and September of 1987. Affected calves ranging from 2 to 9 months of age were selected from the main herd when signs of corneal ulceration were observed. The study was conducted in 2 phases. For phase I, the affected calves of herd 1 (n = 21; Holsteins) and herd 2 (n = 43 Angus crossbred), were randomly assigned to 1 of 3 groups, and were either treated with 250 (n = 23) or 375 mg (n = 21) of benzathine cloxacillin, or mineral oil (n = 20) on days 1 and 4. For phase II, affected calves (n = 16; Angus crossbred, 3 to 9 months of age) from herd 2 were treated with benzathine cloxacillin (250 mg). Eight of these calves were retreated on day 4. After treatment, all calves were examined every 72 hours for 16 days. For examinations, a clinical score was assigned to each eye, and the surface areas of photographed corneal ulcers were measured. The ocular secretions were collected and examined culturally for Moraxella bovis. On days 7, 10, and 13, the calves treated with benzathine cloxacillin had significantly (P less than 0.05) lower lesion scores, compared with the controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

A topical aqueous calcineurin inhibitor for the treatment of naturally occurring keratoconjunctivitis sicca in dogs

Purpose The purpose of this study was to evaluate the efficacy of an aqueous calcineurin inhibitor, SCY‐641, in the treatment of naturally occurring canine immune‐mediated keratoconjunctivitis sicca (KCS). Methods A randomized, double‐masked, placebo‐controlled clinical study of 56‐day duration was performed in dogs with naturally occurring immune‐mediated KCS assigned to treatment with either topical twice‐daily aqueous calcineurin inhibitor solution (SCY‐641) or artificial tears (placebo) by the study administrator. Clinical examination and Schirmer tear tests (STT) were performed prior to therapy and at days 7, 14, 28, and 56 after initiation of treatment. Results Twenty dogs were enrolled in the study with ten receiving placebo and 10 receiving SCY‐641 in one or both eyes. No adverse effects were noted with any treatment. There were no significant differences in mean STT values in dogs in group either at day 0 (prior to therapy) or after 7 days of treatment. At 14, 28, and 56 days after initiation of treatment, mean STT and increase in STT over baseline in dogs treated with SCY‐641 were significantly higher than in dogs treated with placebo (P < 0.04). Conclusions SCY‐641 was well tolerated by dogs with naturally occurring KCS, and by 14 days after initiating therapy, dogs treated with SCY‐641 had significantly higher STT than placebo‐treated dogs. These preliminary results indicate that topical SCY‐641, in a stable clear aqueous solution, is efficacious in a spontaneous model of KCS and warrants further evaluation as a treatment of immune‐mediated KCS.     

Observations on the efficacy of mass treatment by subconjunctival penicillin injection for the control of an outbreak of infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis was diagnosed on a Manawatu beef cattle farm, with inflammation of 85% of eyes in a group of 150 6-month-old-calves. Comeal inflammation was recorded in 23% of eyes. All active lesions healed over a 3-week period following whole group subconjunctival penicillin injection. Morarellu bovis was cultured from two of seven conjunctival swabs at the time oftreatment and from four of six conjunctival swabs 9 days after treatment. Concurrently, pink-eye was noted in older cattle, with inflammation in 50% of eyes. For practical handling reasons, these older cattle were not treated. Despite nontreatment, their clinical signs regressed over a 3-week period. The rationale of whole group treatment for the control of infectious bovine keratoconjunctivitis is discussed.     

Efficacy of a long-acting formulation of ceftiofur crystalline-free acid for the treatment of naturally occurring infectious bovine keratoconjunctivitis

OBJECTIVE: To evaluate the efficacy of ceftiofur crystalline-free acid (CCFA) administered into the posterior aspect of an ear for treatment of corneal ulceration associated with naturally occurring infectious bovine keratoconjunctivitis (IBK). ANIMALS: 78 beef calves located at Sierra Foothills Field Station (SFS) and 52 calves located at a commercial dairy (CD). All calves were from 3 to 9 months old. PROCEDURE: At each site, calves were randomly allocated to 1 of 2 treatment groups by use of a block design determined by corneal ulcer size. A single dose of CCFA (6.6 mg of ceftiofur equivalents/kg, s.c.) was administered into the posterior aspect of a pinna. A second group of calves received a single dose of vehicle (0.03 mL/kg, s.c.; controls). Corneal ulcers were photographed, and clinical signs were assessed in calves every 3 to 4 days for 21 days. RESULTS: A positive treatment effect was detected at SFS. Results at the CD were inconclusive because ulcer healing occurred rapidly in control and CCFA-treated calves. At SFS, treatment with CCFA resulted in shorter mean healing times, smaller corneal ulcer surface area measurements, amelioration of ocular discharge and photophobia, and a 50% increase in the percentage of calves healed by day 14. After adjustment for initial corneal ulcer size, treatment with CCFA resulted in a 4-fold increase in the odds of corneal ulcer healing by day 14, compared with controls. CONCLUSIONS AND CLINICAL RELEVANCE: A single dose of CCFA administered into the posterior aspect of a pinna had a positive treatment effect against naturally occurring IBK in calves with corneal ulcerations.     

Prevention of naturally occurring infectious bovine keratoconjunctivitis with a recombinant Moraxella bovis pilin-Moraxella bovis cytotoxin-ISCOM matrix adjuvanted vaccine

To evaluate the efficacy of a recombinant Moraxella bovis pilin-M. bovis cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK; pinkeye), a randomized, blinded, controlled field trial was conducted during summer 2005 in a northern California herd of beef cattle. One hundred and one steers were vaccinated with ISCOM matrix (adjuvant control), recombinant M. bovis cytotoxin carboxy terminus+ISCOM matrix (MbxA), or recombinant M. bovis pilin-cytotoxin carboxy terminus+ISCOM matrix (pilin-MbxA); calves received secondary vaccinations 21 days later. Calves were examined once weekly for 18 weeks for the development of corneal ulcers associated with IBK. Overall, the pilin-MbxA vaccinated group had the lowest overall cumulative proportion of ulcerated calves. Calves that received MbxA, whether alone or with pilin had significantly higher M. bovis cytotoxin serum neutralizing titers as compared to control calves. Results of ocular cultures suggested that vaccination with an M. bovis antigen affected organism type isolated from an ulcer: M. bovis was cultured more often from the eyes of control calves than from the eyes of calves vaccinated with MbxA and pilin-MbxA. In addition, vaccination of calves with MbxA and pilin-MbxA resulted in a higher prevalence of Moraxella bovoculi sp. nov. in ocular cultures. While no significant difference was observed between a cytotoxin versus pilin+cytotoxin vaccine against IBK, the reduced cumulative proportion of IBK in the pilin-cytotoxin vaccinated calves suggests it may provide an advantage over a cytotoxin vaccine alone. Efficacy of an M. bovis vaccine may be reduced in herds where IBK is associated with M. bovoculi sp. nov.     

A national survey of the clinical features, treatment and importance of infectious bovine keratoconjunctivitis

SUMMARY A postal survey of cattle producers throughout Australia was conducted to obtain information concerning the occurrence, signs and treatment of infectious bovine keratocojunctivitis, animal breeds, animal numbers and types, environmental conditions under which the animals were kept and management routines and systems of the animals (Slatter et al 1982). The most common clinical signs reported were ocular discharge (43.9%), corneal opacity (9.9%), or both (46.1%). The majority of respondents (54.8%) indicated duration of infections of at least 3 weeks. The condition was predominantly unilateral (74.7%) but 22.3% of respondents reported an equal occurrence of the condition unilaterally and bilaterally. The most frequently used drugs were homidium bromide (26.7%), oxytetracycline hydrochloride (22.8%), chloramphenicol derivatives (13.7%) and penicillin derivatives (13.5%). However, described treatment regimes indicated that therapeutic levels of antibiotics would not be maintained in the eyes of treated animals. Producers considered that 75% of affected animals showed reduced rates of weight gain, and 64% indicated they were more difficult to handle. An approximate figure of $22,000,000 was determined for loss of national production due to the disease, based on producers' estimates. In addition, a further cost of $1,566,500 was estimated for the labour involved in current treatment regimes. Beef and dairy producers spent different amounts on medications and treated for different durations. The economic significance of the disease justifies further studies on production losses due to the disease and cost effective methods of treatment.     

Dynamics of Moraxella bovis infection and humoral immune response to bovine herpes virus type 1 during a natural outbreak of infectious bovine keratoconjunctivitis in beef calves

Infectious bovine keratoconjunctivitis (IBK) is an acute disease caused by Moraxella bovis (Mb). Several factors may predispose animals to an IBK outbreak; one commonly observed is infection with bovine herpes virus type 1 (BHV-1). The aim of this study was to investigate the dynamics of BHV-1 virus infection and its relation with clinical cases of IBK in weaned calves from a beef herd with a high prevalence of lesions caused by Mb. Sampling was carried out in six stages and included conjunctival swabs for isolating Mb as well as blood samples for identifying antibodies specific for BHV-1. A score for IBK lesions after observing each eye was determined. The findings of this study showed a high prevalence of BHV-1 virus infection (100% of animals were infected at the end of the trial); 67% of animals were culture-positive for Mb, but low rates of clinical IBK (19% of calves affected) were detected at the end of the trial. These results suggest that infection with BHV-1 did not predispose these animals to IBK, and that Mb infection produced clinical and subclinical disease in the absence of BHV-1 co-infection.     

Efficacy of florfenicol in the treatment of experimentally induced infectious bovine keratoconjunctivitis.

OBJECTIVE: To evaluate efficacy of florfenicol in an induced model of infectious bovine keratoconjunctivitis, using a blinded randomized, controlled trial. ANIMALS: 48 male Holstein calves, 2 to 4 months old. PROCEDURE: Moraxella bovis infection was induced in all calves. When corneal ulcers developed, each calf was assigned randomly to 1 of 3 treatment groups, using a block design determined by corneal ulcer size (day 0). Calves were treated with florfenicol (20 mg/kg of body weight, IM) on days 0 and 2 (IM group; n = 16). Calves of a second group received a single dose of florfenicol (40 mg/kg, SC) on day 0 (SC group; n = 16). The third group of calves was not treated (control group; n = 16). Corneal ulcers were photographed, and each calf was assessed for 30 days after treatment for 10 clinical signs of infection. Corneal ulcer surface areas were measured, and clinical scores were calculated. Ocular secretions for microbiologic culture were obtained weekly from each eye. RESULTS: A Cox regression model indicated that, after adjustment for initial ulcer size, healing rates were 6.2 and 4.8 times greater in calves of the IM and SC groups, respectively, compared with the control group. Clinical scores and surface area measurements for treatment groups were significantly smaller than those for controls during posttreatment weeks 1 through 4. From day 8 through day 29, M bovis was isolated from ocular secretions of 14 of 16 control calves and 1 of 32 treated calves. CONCLUSIONS AND CLINICAL RELEVANCE: Parenterally administered florfenicol reduces corneal ulcer healing time, lessens clinical severity, and reduces the amount of bacterial shedding from calves infected with M bovis.     

Survival analysis for evaluation of corneal ulcer healing times in calves with naturally acquired infectious bovine keratoconjunctivitis

A clinical trial examining the efficacy of 2 drugs for treatment of a natural epizootic of infectious bovine keratoconjunctivitis was performed. The study was conducted in 103 grazing Hereford calves during the summer of 1985. The calves were prospectively and randomly assigned to 1 of 3 groups at the beginning of the study on June 17, and were examined 3 times weekly thereafter until the final observation on August 6. Calves in group 1 (n = 34) were not treated and were used as controls. Calves of group 2 (n = 34) with corneal ulcers were treated with a long-acting oxytetracycline formulation (OTC group). The parenteral treatment was repeated in 72 hours. Affected calves of group 3 (n = 35) were treated topically with furazolidone spray when they developed new corneal ulcers, or when existing lesions worsened during subsequent examination periods (NFZ group). Healing times of the corneal ulcers were reported in 3 ways: the combined times for ulcers present in both eyes of a calf simultaneously (method A), independent times of each ulcer on a calf (method B), and time of the first ulcer for each calf (method C). Censored healing times were examined as left censored (ulcer present at the beginning of the study), right censored (ulcer not healed at the end of the study), or uncensored (true) healing times. The effect that the treatments had on healing times were investigated by use of notched box and whisker plots, life tables, and Cox regression models. The analysis indicated that treatment of calves with either antimicrobial reduced the healing time of corneal ulcers, compared with untreated controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Topically applied furazolidone or parenterally administered oxytetracycline for the treatment of infectious bovine keratoconjunctivitis

The effectiveness of topically applied furazolidone (FZ) or parenterally administered oxytetracycline (OTC) for treatment of infectious bovine keratoconjunctivitis was determined in a field study. Between June 13 and Aug 6, 1985, a study was conducted on a ranch in northern California. Eyes of Hereford calves (n = 103) were examined 3 times each week for 7 weeks. After daily examinations on June 13 and 14, calves were allotted randomly to 3 groups. On June 17, calves (that had corneal ulcers) of groups 1 (n = 35) and 2 (n = 35) were treated with OTC and FZ, respectively. Treatments were administered again only if new ulcers were observed, if an existing ulcer worsened, or if a healed ulcer recurred. Calves of group 3 remained untreated (controls). Corneal ulcers developed in 35 of the FZ-treated calves, in 33 of the OTC-treated calves, and in 33 of the untreated calves. Corneal perforations were observed in 3 untreated and 2 FZ-treated calves but were not observed in any OTC-treated calves. Panophthalmitis developed in one eye of an untreated calf. Corneal ulcers in the OTC-treated calves were smaller and healed more rapidly than did corneal ulcers in calves of the other groups. By the 22nd day of the study (July 3), the number of OTC-treated calves with corneal ulcers was less than that of the other 2 groups. Calves of the OTC treatment group had the fewest multiple corneal ulcer recurrences, but calves of all 3 groups had a similar number of single corneal ulcer recurrences.(ABSTRACT TRUNCATED AT 250 WORDS)     

First report of the use of mucosal swabs of the palatine tonsillar crypt for detection of Mycoplasma bovis in naturally infected calves

ABSTRACT

Aims: To compare detection by real-time PCR of DNA from Mycoplasma bovis on mucosal swabs taken from the palatine tonsillar crypt and the mainstem bronchi of clinically asymptomatic calves after slaughter.

Methods: We compared the sensitivity of mucosal swabs taken from two sites: the palatine tonsillar crypt and the mainstem bronchi. Paired samples were taken post-mortem at slaughter from 55 clinically well calves from an infected herd and were tested by real-time PCR for the presence of M. bovis-specific DNA.

Results: Mycoplasma bovis DNA was detected in 51 palatine tonsillar crypt swabs (92.7 (95% CI?=?82.4–98.0)%) and seven mainstem bronchial swabs (12.7 (95% CI?=?5.3–24.5)%). All seven calves with positive mainstem bronchial swabs also had positive palatine tonsillar crypt swabs.

Conclusions: When compared to mucosal swabs of the mainstem bronchi, mucosal swabs of the palatine tonsillar crypt were seven times more sensitive for the post-mortem detection of M. bovis DNA. The viability of detected M. bovis was not assessed, because any cattle carrying viable or non-viable M. bovis DNA were determined to be a potential risk to eradication. Palatine tonsillar crypt mucosa may be a useful anatomical site for real-time PCR detection of M. bovis DNA in naturally infected calves. More work is needed to define the persistence and viability of M. bovis at this anatomical site.

Clinical relevance: The results of this study helped form the basis of surveillance tools used in M. bovis control and eradication efforts. Familiarity with these results may help veterinarians better communicate with their clients about the science behind the eradication efforts.