Biosecurity and isolating new horses

Most infectious disease arrives on a property with a horse: a new purchase, an agistee, or your own horse coming home from a show. Biosecurity is the set of habits that stops it spreading – isolating new arrivals, keeping gear separate, and acting fast when a horse gets sick.

Agriculture Victoria puts it plainly: horse owners, trainers and service providers all play a part, and some horse diseases can also infect people (Agriculture Victoria – biosecurity for horses). New Zealand's Code of Welfare recommends measures for isolating incoming and sick horses to avoid spreading disease (MPI Code of Welfare).

Your vet is your best partner for biosecurity. Talk to them about the diseases common in your district and about testing new horses before they join the herd.

How long to isolate a new horse

Guidance varies with the disease you're guarding against:

• Agriculture Victoria recommends that new, returning or visiting horses are ideally quarantined separately for at least 10 days, and checked daily for signs of ill health and injury, and to make sure they're eating and drinking (Agriculture Victoria – biosecurity).
• Victoria's Code of Practice recommends a new horse is quarantined away from the established group for 10–14 days (Code of Practice).
• For strangles specifically, an international consensus statement by the American College of Veterinary Internal Medicine recommends isolating new arrivals for at least 3 weeks, with screening for carriers as part of the programme (ACVIM strangles consensus, Boyle et al. 2018).

Why longer for strangles? The ACVIM statement explains that some horses carry the bacteria in their guttural pouches (air sacs in the head) for months or years while looking completely healthy, and can shed it intermittently. A blood test followed by a guttural pouch check can identify these carriers. Ask your vet whether screening is worthwhile for your new horse.

Setting up an isolation area

You don't need a purpose-built facility. The aim is to stop direct contact and indirect spread through shared gear, water and people.

• No nose-to-nose contact. Use a paddock or yard well away from other horses. Where space is tight, the ACVIM statement describes separating groups with two layers of electric fence to prevent nose-to-nose contact (ACVIM consensus).
• Separate water. Don't share troughs. The ACVIM statement notes the strangles bacterium can survive in water for 4–6 weeks.
• Separate gear. Give the isolated horse its own buckets, feed bins, grooming kit, headcollar, rugs and tack. Label or colour-code them.
• Look after it last. Feed and handle isolated horses after all the others, and wash your hands and change or clean boots and outer clothes afterwards.
• Keep it close enough to watch. You'll want to check temperature, appetite, manure and any nasal discharge every day.

Agriculture Victoria also recommends cleaning and disinfecting tack and equipment between horses (Agriculture Victoria – biosecurity).

Monitoring during isolation

Take the horse's temperature daily if it's used to it. In strangles, the ACVIM statement says fever with lethargy is usually the first sign, appearing 3–14 days after exposure, and nasal shedding usually begins 2–3 days after the fever starts. That window means a horse picked up early by its temperature can be isolated before it becomes infectious (ACVIM consensus).

Also watch for nasal discharge, cough, swollen glands under the jaw, reluctance to eat, or diarrhoea. See signs of a healthy horse for normal ranges.

If you suspect strangles: outbreak steps

Strangles is a highly contagious bacterial infection of the upper airway. If you suspect it, call your vet and follow their plan. The ACVIM statement recommends these control measures (ACVIM consensus):

1. Isolate the sick horse immediately.
2. Stop all horse movements on and off the property.
3. Sort horses into three groups:
   • Red – horses showing signs.
   • Amber – horses that have had direct or indirect contact with a red horse and may be incubating.
   • Green – horses with no known contact.
4. Take temperatures of amber and green horses twice a day, and move any horse with a fever to the red group.
5. Use colour-coded buckets and gear so nothing moves between groups. Don't share water, and disinfect water and feed buckets daily.
6. Use separate people for each group if possible. If not, always work from green to amber to red, never back.
7. Keep quarantine in place for at least 3 weeks after the last case has resolved and horses have tested negative. The statement warns that recovered horses may be infectious for at least 6 weeks after their discharges dry up.

Your vet will advise on testing to confirm recovered horses aren't carriers before they rejoin the herd.

Reporting: in Victoria, strangles is a notifiable disease that must be reported within 7 days (Agriculture Victoria – notifiable diseases of horses). Reporting rules differ between states, so ask your vet about yours. See horse vaccinations for strangles vaccination.

Emergency and notifiable diseases

Some horse diseases must be reported to government quickly. In Victoria, Agriculture Victoria lists equine influenza and Hendra virus among notifiable diseases, and asks anyone who suspects an emergency animal disease to contact their vet or the Emergency Animal Disease Hotline on 1800 675 888 (Agriculture Victoria – biosecurity).

Hendra virus (Australia): NSW DPI says Hendra should be considered in any horse with a sudden illness and rapid decline with severe nervous or respiratory signs and no current Hendra vaccination. If you suspect it, keep people and pets away and call your vet immediately (NSW DPI – Hendra virus). Hendra can infect people. Agriculture Victoria notes Hendra has only occurred in horses in Queensland and NSW to date, but all areas where flying foxes and horses live together are considered at risk (Agriculture Victoria – biosecurity).

New Zealand: if your horse shows unusual signs that could be an exotic disease, talk to your vet and call MPI's Exotic Pest and Disease Hotline on 0800 80 99 66 (MPI – report a pest or disease).

Everyday yard hygiene

Agriculture Victoria lists the common ways disease gets onto a property, and what to do about each (Agriculture Victoria – biosecurity):

• New and returning horses: treat any horse coming home from a show or event as a possible risk, and quarantine it.
• Feed and bedding: check deliveries for contaminants, with a commodity vendor declaration where possible.
• Access points and visitors: use signs, provide boot and equipment washing, have a designated visitor parking area, and ask visitors to arrive with clean footwear and clothing.
• Boundaries: keep fences in good repair. Double fencing helps.
• Pests: control rodents, keep feed in rodent-proof containers, and use good drainage and manure management to cut insect breeding.
• Equipment: clean and disinfect tack and gear between horses.
• Training: make sure everyone on the property knows the routine.
• Records: keep records of horse movements, visitors, feed and bedding deliveries and health treatments, so contacts can be traced.

Victoria's Code adds that good hygiene in and around stables, yards and paddocks, including disposal of manure and used bedding, reduces the risk of parasites and disease (Code of Practice). The BHS Stage 2 syllabus includes isolation, where needed, in caring for an unwell horse (BHS Stage 2 Care).

Register your property

In Victoria, horse owners and keepers are required by law to have a property identification code (PIC) for the property where a horse is kept, including agistment properties. PICs let authorities contact owners during disease outbreaks, fires and floods (Agriculture Victoria – biosecurity). Other states have their own rules; see our agistment guide.

If you run a yard with several owners, write your biosecurity rules into your agistment agreement. See running a horse yard.

FAQ

How long should I isolate a new horse?

Agriculture Victoria recommends at least 10 days (Agriculture Victoria), and Victoria's Code 10–14 days (Code of Practice). For strangles, an international consensus recommends at least 3 weeks plus carrier screening (ACVIM).

Can a healthy-looking horse spread strangles?

Yes. Some recovered horses carry the bacteria for months or years without signs (ACVIM). Ask your vet about screening.

Should my horse be isolated after a show?

Agriculture Victoria suggests treating horses returning from shows or events as a potential risk and quarantining them separately (Agriculture Victoria).

Is strangles notifiable?

In Victoria, yes – it must be reported within 7 days (Agriculture Victoria). Check the rules in your state or with your vet.