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Although these guidelines are primarily intended for the prevention and control of venereally transmitted diseases, they are also useful for control of other infectious diseases caused by viruses, bacteria and parasites. Other AAEP guidelines available to members on the AAEP website (e.g., Infectious Disease Control Guidelines and Vaccination Guidelines) are recommended reading. Even though not strictly speaking correct, in this document, the term horse will be used to refer to all equids (horse, donkey, mule, and pony). 

The emphasis of the Biosecurity Guidelines for Control of Venereally Transmitted Diseases is to control the transmission of: 

            Taylorella equigenitalis (Contagious Equine Metritis Organism; CEMO)
            Equine arteritis virus (EAV)
            Equine herpesvirus-3 (EHV-3; equine coital exanthema virus) 

Although not included in the foregoing list, mention should be made of Trypanosoma equiperdum, the cause of dourine that the United States has been free from for many years.  Dourine is a venereally transmitted disease of equids (ie, horses, donkeys, mules).  This organism can be recovered from the uterus in acutely infected female equids that have genital discharges.  Edema is also a characteristic of the disease, and development of edematous ‘silver dollar placques’ is considered pathognomonic for the disease.  Transmission of dourine takes place almost exclusively by coitus, principally from an infected stallion to a mare.  While spread of the causal agent has not been confirmed by artificial Insemination (AI), this could potentially occur since T. equiperdum is present in seminal fluid.  Appropriate samples for the diagnosis of dourine include blood, serum, and edematous fluid obtained by aspiration.  If the disease is suspected, state and federal health authorities must be notified.  Treatment is not permitted.  Since dourine is a transboundary disease in the US, any confirmed cases must be euthanized.  Moreover, even if permitted, treatment would not necessarily eliminate T. equiperdum from the reproductive tract and infected animals would remain inapparent carriers. 

Other infectious agents, such as the bacteria Pseudmomonas aeruginosa and Klebsiella pneumoniae) have been incriminated as venereally transmissible pathogens; however, there is lack of scientific information on the pathogenicity of different strains of these bacteria and their ability to cause disease.  For example, there is evidence that only a few capsule types of Klebsiela pneumoniae and only a few serotypes of Pseudomonas aeruginosa are truly venereal pathogens.  Accordingly, simply recovering either of these two organisms using standard aerobic culture techniques is not of itself sufficient proof that either bacterium is inherently pathogenic and a cause of venereal disease.  Very few laboratories currently offer capsule typing or serotyping services for either bacterium.  Nevertheless, mares susceptible to infection can develop endometritis when exposed to pathogenic organisms at the time of breeding. 

Venereally transmitted diseases are of great concern to horse breeders and veterinarians involved in breeding management of mares and stallions.  Whether horses are part of a natural breeding program or an AI program, some of these diseases are highly contagious and have been shown to be transmittable between animals by direct horse-to-horse contact, through use of contaminated semen, or by indirect venereal contact by the use of contaminated semen collection and processing equipment (including artificial vaginas and breeding phantoms) and personnel (hands and clothing) participating in the semen collection process.  These guidelines are specifically written and endorsed by the American Association of Equine Practitioners to help protect horses and breeding facilities from the economically damaging consequences of such diseases.