Performing Department
Medicine & Epidemology
Non Technical Summary
Infectious bovine keratoconjunctivitis (IBK) caused by Moraxella bovis is the most common ocular disease of cattle in the United States. IBK causes in pain, impaired vision, reduced weight gains and necessitates treatment with antibiotics. Prevention is important for improving cattle health and welfare, reducing antibiotic usage and economic losses. Commercial vaccines are available, however, they are not effective in randomized clinical trials. Another approach to preventing disease is augmentation of the host's immune system. Cattle possess an enzyme system present in respiratory tract, udder and mucous membranes that naturally forms potent antimicrobial products when supplemented with iodine as a substrate. We have found that oral dosing of cattle with sodium iodide achieves effective antibacterial concentrations of iodide in airway secretions and tears, however oral dosing is not practical in a field setting. Ethylenediamine dihydroiodide (EDDI) is a common iodine source for cattle mineral mixes and is currently approved for prevention of iodine deficiency. New animal drug application (NADA) approval from FDA is necessary to legally supply iodine for treatment or prevention of disease, therefore this project seeks to gather pilot data needed for approval and future herd based trials of efficacy.The goals of this study will be: 1. Determine the minimal concentration of iodine, in the above mentioned enzyme system, necessary to inactivate M. bovis in vitro. 2. Determine if this level of iodine is achievable in bovine tears by feeding free choice mineral mix containing target levels of EDDI.
Animal Health Component
100%
Research Effort Categories
Basic
40%
Applied
60%
Developmental
(N/A)
Goals / Objectives
Infectious bovine keratoconjunctivitis (IBK) caused by Moraxella bovis is the most common ocular disease of cattle in the United States. Affected cattle exhibit corneal ulceration and edema, pain, photophobia, lacrimation and in severe cases partial or total vision loss. Commercial vaccines have not been effective in randomized clinical trials[1]. Another approach to preventing disease is to augment the host's immune system. One mechanism of augmenting the host innate immune system described in cattle consists of lactoperoxidase (LPO), hydrogen peroxide (H2O2), and halide ions [2]. Lactoperoxidase catalyzes the oxidation of halide ions using hydrogen peroxide to form potent antimicrobial products. Typically, thiocyanate serves as the physiologic substrate for this reaction, however, our recent work has shown potent antiviral and antibacterial properties of hypoiodous acid, the product of iodide ion oxidation by LPO and hydrogen peroxide, in vitro [3-5]. Additional work by our group has shown that oral dosing of cattle with sodium iodide (NaI) achieves concentrations of iodide in respiratory secretions that correspond to effective concentrations in vitro and that these levels persist for at least 72 hours after a single dose [6]. While oral dosing with sodium iodide is not practical due to the labor involved, iodine can also be supplemented orally via mineral mix. Ethylenediamine dihydroiodide (EDDI) is a common iodine source for cattle mineral mixes and is currently approved for prevention of iodine deficiency. New animal drug application (NADA) approval from FDA is necessary to legally supply iodine for treatment or prevention of disease (other than iodine deficiency) or to be fed at a higher level, therefore this project seeks to gather pilot data needed for approval and future herd based trials of efficacy.SPECIFIC OBJECTIVES1. Determine the direct effect of LPO/iodine system against M. bovis and titrate iodine levels to lowest effective concentration.2. Determine iodine levels in tears and serum from cattle fed EDDI via a mineral mix formulated based on minimum effective concentration from Objective 1.
Project Methods
1. To determine the in vitro susceptibility of the bacterial pink eye pathogens (M. bovis, M. bovoculi) to inactivation by the LPO/H2O2/iodine system, hypoiodous acid (HOI), the functional antimicrobial molecule, will be generated in vitro using bovine milk derived LPO (Sigma, catalog number L2005), NaI and H2O2. Bacterial isolates will be obtained from John Angelos. Standardized concentrations of bacteria will be exposed to varying concentrations of NaI, ranging from 5- 250mM, and appropriate controls will be run in parallel. To determine the kinetics of bacterial inactivation, subsamples will be removed prior to catalyst and at 5 minute and 30 minute time points and plated on blood agar in 10 fold serial dilutions to determine bacterial counts. All experiments will be performed in triplicate. 2. To determine if [I] to inactivate M. bovis in vitro are achievable with oral supplementation of iodine in a mineral mix, a feed trial will be done using 7 cull animals (calculated sample size of 5 based on data from pilot study in dairy calves, plus two additional in case of illness) purchased from a single farm identified by Co-I Davy, or from auction (single source is preferable). Animals will be housed at VMTH in group pens where handling facilities for tear and serum collection are accessible. After a 3 day acclimation period with daily physical exams to ensure healthy subjects, a feeding trial of two mineral mixes containing a high and low concentration of EDDI will done. The range of [I] in the mineral mix will be based on: target tear iodine concentration determined in Objective 1, serum iodine levels from publication on oral supplementation in cattle (ranging from 50-200mg/head/day) [8] and preliminary data regarding correlation of tear and serum iodine concentrations from pilot study in dairy calves. Tear and serum samples will be obtained on day 0, before feeding mineral, and on days 1,3 and 5. After day 5, mineral will be discontinued and samples will be collected daily for 5 more days (based on data from previous study). After 5 day washout period the study will be repeated using mineral mix with high iodine concentration. Samples will be submitted to Michigan State diagnostic lab for iodine quantification and pharmacokinetic analysis will be performed. Anticipated results: We predict that between 25-100 μM iodine will be necessary to inactivate M. bovis in vitro and feeding a mineral mix containing sufficient iodine will achieve equivalent concentration in tears in vivo. This data is necessary for NADA approval so field trials can be conducted with trial animals able to enter the food chain. The ultimate goal is to decrease pinkeye and pinkeye treatments on farm, using a technique that is practical for producers to accomplish. Pitfalls/Limitations: A major pitfall would be target concentration of iodine in tears via voluntary intake is unachievable due to palatability issues from additional EDDI. Intake will be observed and compared between high and low [I] to gain insight into palatability effects of EDDI.