Equine Genital Herpes
What is equine genital herpes? If this term is not familiar to you, let me explain the fact surrounding EHV (Equine Herpes virus). The equine herpes virus (EHV-3) causes equine genital herpes. This is a moderately large virus that infects horses. The equine genital herpes virus would lie dormant and establish latency and at some point in their life, it can be reactivated when the animal is stressed. There are four serotypes of the equine herpes virus some of which can cause different clinical signs and diseases. EHV -3 causes coital exanthema, which is transmitted through breeding or in short horses’ sexual intercourse.
EHV-3 causes equine genital herpes in mares and stallions 4 - 7 days after contact with the virus. The infection can be worse in the stallion than the mare. Clinical signs in the stallion may include dullness, fever, and anorexia. The first visible sign is the appearance of vesicles up to 1.5 cm in diameter that first develop on the penis and then 2-5 days later on the prepuce. On the other hand, the initial appearance in the mare is small (2mm) circular bumps on the vulva that develop into vesicles and then will rupture and cause lesions or open wounds that will heal in about 2-4 weeks. The areas may scar, leaving spots without pigment. Some stallions may refuse to breed during this time, but others will continue to breed even while many penile lesions are present.
EHV -3 that causes equine coital exanthema (equine genital herpes) is transmitted primarily by breeding or cross breeding. Usually a mare that is infected but not showing clinical signs spreads the virus to the stallion, and then he transmits the virus to susceptible mares and so on and so forth. If you want to make sure what type of EHV infected your horse, have your veterinarian take a blood sample at the start of the clinical signs. This is more effective in finding out if there has been an increase in your horse’s antibody levels. This is usually performed in the laboratory. This technique may not be useful in abortion cases and another lab test procedure called PCR may be required to diagnose the disease.
There are currently no specific antiviral drugs that treat equine genital herpes that are approved for use in horses. However, there are treatments that are helpful in reducing clinical signs, preventing secondary bacterial infections and minimizing stress. Treatments of equine genital herpes include vaccination. Although vaccination is not preventive, however they may decrease the risk of disease. Both modified live and killed vaccines are available for EHV-1 and -4, and are sometimes combined with equine influenza virus vaccine. In some cases Acyclovir may be used off label to help reduce clinical signs of EHV-3 virus.





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