Strangles in Horses: How the Lab Confirms It

Strangles is a contagious bacterial infection of horses that causes fever, a thick nasal discharge and swollen glands under the jaw. The lab can help confirm it with RT-PCR, a test that finds the germ's genetic material, on a nasal swab, a guttural pouch wash or pus from an abscess. Your vet chooses the sample.

What are the signs of strangles?

The early signs are fever, dullness, less interest in feed and a thick nasal discharge. The glands under the jaw and in the throat swell, turn hot and sore, and may burst and release thick pus. Swallowing can hurt, so a horse may eat less or let feed drop from its mouth.

In some horses the swelling presses on the throat and makes breathing noisy or hard. That is an emergency, and you should call a vet at once. Young horses are often hit hardest.

How does it spread, and what is a carrier?

Strangles passes from nose to nose, and also on shared water troughs, buckets, feeding areas, tack and the hands and clothes of handlers. A horse that looks well can still carry the germ, so any horse with a fever and a discharge should be kept away from the others until a vet has seen it.

Some horses that have recovered go on carrying the germ in their guttural pouches, which are two air-filled pockets behind the nose and throat. A carrier may shed the germ from time to time without looking ill, and may start trouble in another stable.

Until the vet arrives, keep the sick horse's bucket, brush and rug separate, and wash your hands after handling it before you touch any other horse.

Which samples can the vet take?

• Nasal swab. A long, soft swab is passed gently into the nostril and turned against the lining, then placed in its tube. A fresh swab is used for each horse.
• Guttural pouch wash. The vet rinses the pouch with clean fluid through a thin tube and collects the liquid. It is especially useful when looking for carriers.
• Pus. When an abscess has burst or been opened by the vet, a sample of the pus can be collected.

Restraining a horse for these samples takes skill and care, which is why the vet usually does it.

RT-PCR or culture?

The Strangles (Streptococcus equi) RT-PCR looks for the genetic material of the bacterium. It can find the germ even when only a little is present, and it can find traces of bacteria that are no longer alive. Culture is the older way: the sample is placed on a dish so that living bacteria can grow. It needs live germs and some waiting, but some vets still ask for it as well.

A negative result from one sample does not always rule strangles out. The germ may sit deep in the pouches, or be shed only now and then, and a swab may miss it. Your vet may repeat the test, take a pouch wash or add culture before calling a horse clear.

What do the blood tests add?

A Complete Blood Count (CBC) can show signs that the body is fighting infection, such as a change in the white cells. The Equine Serum Amyloid A (SAA) measures a protein that rises quickly with inflammation and falls as the horse recovers. Neither test names strangles, but both help your vet follow how sick a horse is and whether it is improving.

For a horse with fever and cough, the Horse Fever & Respiratory RT-PCR Panel typically groups influenza, herpesvirus and strangles RT-PCR with a blood count and SAA. The exact list is confirmed when you book.

A registered veterinarian reads all these results together with the horse's signs, its contacts and its history. Never delay a vet visit for a horse with a swollen throat or trouble breathing.

Read next

Strangles is only one cause of fever and cough in horses, and Equine Influenza and Herpesvirus: Fever and Cough Tests covers two viral causes. For a plain account of how the swab itself is taken and handled, read How Swabs and Samples Are Taken for RT-PCR Tests.

Testing in Bhopal

A vet usually takes the swab, wash or pus sample, and the lab at C-200, C Sector, Shahpura can collect it from your stable free of charge anywhere in Bhopal. If you are in another district, ask your vet to send it by courier or bus parcel. Call or WhatsApp +91 88175 01118 to book; the lab confirms the method, sample needs and reporting time at that point.