11/08/2025
📢 Equine Herpes Virus (EHV)
There are 5 common strains of Equine Herpes Virus (EHV-1, -2, -3, -4 and -5), that are endemic in Australia, meaning that they have all been here for a long time and are widespread across the country. EHV-1, -2 and -4 all cause respiratory disease in young horses and most horses have been exposed to EHV-1, -2, -4 and -5 by the time they are weaned without showing many, if any, signs. If the horse wasn't exposed a foal and is susceptible, becomes infected with a different strain or suffers a relapse at the wrong time, then the clinical signs can be serious.
📌EHV-1 and -4 are highly contagious respiratory viruses, that are very easily spread by nose-to-nose contact, sneezing/coughing, droplet contamination and exposure to aborted foetal fluids.
📌EHV-4 is usually a self-limiting virus that decreases performance for the few days of fever and malaise.
📌EHV-1 has 3 different clinical presentations:
1️⃣Respiratory disease
✔️Mild but performance limiting upper respiratory infection in adults
✔️Severe pneumonia in neonatal foals born of recently infected mares, which can be fatal
2️⃣Abortion
✔️In mares infected most commonly in the last trimester. Due to how contagious the virus this is, it can end up in abortion storms where most of the mares in a paddock will abort.
3️⃣ Neurological disease
✔️Rare!
✔️Can present with fever, ataxia, weakness, trouble standing, dog sitting (rear limbs often more severely affected than forelimbs), paralysed tail region – dripping urine difficulty passing manure, floppy tail.
✔️Neurologic EHV-1 can often be fatal.
✔️Unlike Hendra, which can present the same way, EHV is not contagious to people.
🛑Horses suspected to have EHV-1 should be immediately quarantined and veterinary assistance sort to implement strict biosecurity and hygiene procedures to prevent further spread. If your mare aborts especially after having a runny nose or being “a bit off”, then please contact your vet to get the mare and -1the foal tested for EHV-1.
💉There is a vaccine available for EHV-1 and -4, which helps decrease clinical signs and aids in the prevention of abortions. Mares should have a starter course of 1 vaccine 4 weeks apart starting after their 45 days positive pregnancy test and then a booster vaccination at 5,7 and 9 months of gestation.
Competition horses can be vaccinated with an initial course (2 vaccinations, 4 weeks apart) and then a 6 monthly vaccination. Other methods to minimise spread is to quarantine all new horses (especially mares) coming on to the property for at least 3 weeks, keeping the pregnant mares in small, stable groups with minimal social stresses; avoid prolonged transport and mass weaning of a large number of foals together.
FYI - EHV-3 is an STD that results in blisters and ulcers on stallions and mares and other then having to be benched for 3 weeks during their busy season, doesn't affect them greatly.
☎️Please don’t hesitate to contact the clinic if you want to check whether your horse should be vaccinated and to book them in if necessary, discuss biosecurity measures for your property - plant horses vs competition horses vs brood mares etc, or for any other horse health related matter.
07 49831172
For more information visit:
Equine herpesvirus type 1 (EHV-1) is an animal disease and disorder in Queensland.
