Treatment for contagious equine metritis
FIELD OF THE INVENTION 
     This invention relates to methods for the treatment of contagious equine metritis and more particularly to novel compositions useful for the treatment of contagious equine metritis by topical application. 
     BACKGROUND OF THE INVENTION 
     Contagious equine metritis (CEM) is a highly contagious venereal disease of horses caused by a fastidious, gram-negative cocobacillus. The disease is characterized by a copious water-to-mucopurulent vaginal discharge 2-10 days after breeding by an infected stallion. Shortened estrous cycle links are common and may be the only indication of endometritis in some instances. Carriers of the disease are difficult to detect but outbreaks of the disease have been reported in England, Ireland, France, Australia and in the United States. As reported by Swaney et al, American Journal of Veterinary Research, Vol. 41, January, 1980, pps. 127-132, the causative agent of contagious equine metritis has been identified as Haemophilus equigenitalis, which has ultra-structural characteristics of gram-negative bacteria. The Haemophilus equigenitalis is microaerophilic and unreactive biochemically. It does not depend on hemin (X factor) or nicotinamide adenine dinucleotide (V factor) for growth although hemin stimulates growth. 
     Various proposals have been made for treatment of the disease with modest success. Thus, in the article by Swaney et al, there is disclosure that streptomycin can be used against the bacteria. Further, in the article by John P. Hughes in Theriogenology, published Dec. 8, 1978, it is reported that a wide range of antibiotic and antimicrobial agents have been used either topically, parenterally or in combination at varying dose rates and over different periods of time. Included are suggestions for the use of intrauterine antiseptic solutions, washing with surgical soap, rinsing and applying 0.3% nitrofurazone ointments and the like but the most common treatment is indicated as being the intrauterine infusion of benzyl penicillin or ampicillin for a period of 3 to 5 days. 
     In the article by Henry J. Dabernat et al in Antimicrobial Agents and Chemotherapy, December 1980, pps. 841-843, a review of this disease is disclosed with the statement that the most active drugs are ampicillin, gentamicin, and tetracycline, although a number of other materials were tested with negative results. In an article by S. P. Sahu et al appearing in American Journal of Veterinary Research, Vol. 41, September 1980, pps. 1379-1382, there is described a review of the disease and the use of a citrate-phosphate buffer for a sugar compound to isolate and identify the bacteria but not as a method of treatment. 
     It is evident from this literature that there remains a need in the art for a simple, effective method for the treatment of animals infected with this disease and the present invention provides compositions and methods which are effective for this purpose. 
     SUMMARY OF THE INVENTION 
     It is accordingly one object of the present invention to provide a composition which is effective for the treatment of contagious equine metritis. 
     A further object of the invention is to provide a method for the treatment of contagious equine metritis. 
     A still further object of the present invention is to provide a topical composition and methods for its use in the treatment of contagious equine metritis in horses. 
     Other objects and advantages of the present invention will become apparent to those skilled in the art as the description thereof proceeds. 
     In satisfaction of the foregoing objects and advantages there is provided by this invention a composition for the treatment of contagious equine metritis which comprises an aqueous solution of dextrose or a dextrose metabolite, a buffering mixture of weak organic acids and alkali metal salts of weak organic acids, and a carrier, the composition being characterized as a viscous solution having a pH of about 3.0 to 4.5. Also provided by the present invention is a method for application of this composition to horses for the treatment of contagious equine metritis which comprises topically applying an effective amount of the composition to the external genitalia of stallions and mares. 
     Description of Preferred Embodiments 
     As pointed out above, the present invention is concerned with novel compositions and a method for the treatment of contagious equine metritis, which is a relatively newly recognized venereal disease in horses, the causative organism being Haemophilus equigenitalis. The disease is wide-spread throughout the world and has also been found to be present in horses in the United States. While there are treatments available for the disease as discussed above, primarily by antibiotics, these treatments cause irritation to the mucous membranes. Super bacterial infections, primarily pseudomonas infections, are commonly the end results of the prior art treatment. 
     The present invention provides a novel composition of matter which can be applied topically without the disadvantages and side effects of the prior art treatments. The composition of the present invention in its broadest embodiment comprises an aqueous solution of dextrose or a dextrose metabolite, a buffering mixture of weak organic acids and/or alkali metal salts of weak organic acids, and a carrier, the solution being characterized as a relatively viscous solution having a pH ranging from about 3.0 to 4.5. 
     In several trials the composition was found to be 100% effective in curing horses of the disease if used on three successive days. By comparison antibiotics currently used have to be applied for at least 5 days and are not 100% effective. 
     The most preferred composition may be characterized as containing the following formulation in water in a concentration of about 40-60 weight percent: 
     
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Ingredient      Parts by Weight                                           
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Dextrose        200-300                                                   
Buffering Mixture                                                         
                40-110                                                    
Carrier         80-110                                                    
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     The dextrose component of the composition is dextrose or a dextrose metabolite which is effective to inhibit the contagious equine metritis organism. The dextrose component is an important ingredient as it appears that the dextrose or a metabolite of dextrose inhibits the contagious equine metritis organism. Accordingly, dextrose or equivalent material may be used in the composition. 
     The buffering mixture is also an important ingredient of the composition. A sufficient amount of buffer should be present to provide a resulting solution having a pH of about 3.0 to 4.5, most preferably in the range of 3.2. Any buffer or mixture of buffers can be used for this purpose although mixtures of weak organic acids and alkali metal salts of organic acids are especially preferred. The amount of buffering agent present is also important since the total solution should contain about 8 to 15 weight percent of buffering agents for a suitable composition. 
     The preferred buffering agents are polycarboxylic acids, phosphates, and the like which will provide the required pH range. The most preferred buffers however comprise a mixture of hydroxy polycarboxylic acids having about 3 to 8 carbon atoms and their alkali metal salts, or mixtures thereof. Preferred organic acids include citric acid, malic acid, tartronic acid, tartaric acid, and mixtures thereof as well as the sodium and potassium salts of the acid. A highly preferred buffering system comprises a mixture of citric acid and sodium citrate. 
     It is also preferred that the resulting solution be a viscous solution to inhibit drainage from the infected organs after topical application. Thus, a carrier vehicle is included in the composition to increase the viscosity of the solution. Suitable carries include polyalkylene glycols, methyl cellulose and the like. The preferred carrier vehicle is a lower polyalkylene glycol such as glycerine. 
     The carrier also provides the proper consistency to the composition so that the composition can be used as a lubricant in the treatment of animals such as horses. Thus, the composition will provide both lubricating properties and effectively treat contagious equine metritis on application to horses. 
     A preferred formulation is a 40-60 weight percent aqueous composition of the following materials: 
     
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Ingredient        Amount-Parts                                            
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Dextrose          200-300                                                 
Hydroxy carboxylic acid                                                   
                  25-75                                                   
Alkali metal salt of                                                      
                  40-110                                                  
Hydroxy carboxylic acid                                                   
Carrier           80-110                                                  
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     The most preferred composition for use in the present invention is as follows: 
     
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Ingredient           Amount                                               
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Dextrose             250    grams                                         
Citric Acid          50     grams                                         
Sodium Citrate       25     grams                                         
Glycerine            100    ccs.                                          
Water                400    ccs.                                          
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     The resulting composition is in an aqueous solution with sufficient consistency to drain slowly. In use the composition is applied topically directly to the external genitalia of stallions and mares and preferably is used one time each day for at least two successive days. An effective amount is simply a thorough application of the viscous solution to the external genitalia manually. It has been found that this method will provide 100% effectiveness in curing horses of the contagious equine metritis organism-caused disease. 
    
    
     The following example is to illustrate the invention but the invention is not to be considered as limited thereto. In the Example and throughout the specification, parts are by weight unless otherwise indicated. 
     EXAMPLE 
     The following composition was prepared: 
     
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Ingredient          Parts by Weight                                       
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Dextrose            250     grams                                         
Citric Acid         50      grams                                         
Sodium Citrate      25      grams                                         
Glycerine           100     ccs.                                          
Water               400     ccs.                                          
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     The resulting composition was a viscous solution having a pH of 3.20. 
     To show the effectiveness of the compound twenty horses were selected for testing. Each of the twenty horses was treated with a single treatment of the solution by manually applying topically directly to the external genitalia of the horses. From this test, 17 of the horses were found to be cured by the single treatment. The three horses which were not cured with the single treatment were then treated again with two successive treatments which were found to successfully cure the disease. Accordingly, in the field it is recommended that the disease be treated one time per day with application of the composition on at least two successive days. 
     The advantages in use of the composition of the present invention in the treatment of contagious equine metritis over current therapy and the antibiotics used in the prior art are several. Thus, the horses do not have to be scrubbed prior to treatment, the treatment does not irritate the mucous membranes and the skin, and the treatment does not cause super bacterial infections. Moreover, the treatment is effective for pseudomonas as well as for the contagious equine metritis organism. Moreover, only about two to three treatments are necessary and mares can be treated successfully without removing the clitoral sinuses. 
     The invention has been described herein with reference to certain preferred embodiments. However, as obvious variations thereon will become apparent to those skilled in the art, the invention is not to be considered as limited thereto.