Tick Fever in Horses: Equine Piroplasmosis Testing

Tick fever in horses, called equine piroplasmosis, is an illness caused by two blood parasites, Theileria equi and Babesia caballi, which ticks spread. An RT-PCR test on a blood sample can help detect the parasites, a blood smear can show them under the microscope, and a registered veterinarian reads the results with the horse's signs.

What is equine piroplasmosis?

The two parasites live inside the blood cells of a horse. A tick picks them up while feeding on an infected horse, and later passes them on when it bites another horse. Blood left on a shared needle or instrument can also carry them from one horse to another.

Ticks like warm, sheltered skin. When you groom, look at the ears, the base of the mane, the belly and the inner thighs. Tick numbers often rise in the warm, wet months, so the monsoon is a time to look more often. Ask your vet about tick control for the horse and the stable.

What signs may a horse show?

Common signs include fever, a dull look, a poor appetite, tiredness, weight loss, and pale or yellowish gums. Some horses fall ill suddenly. Others only seem slow, or tire early in work, for a long time. Some show nothing at all.

These signs also fit many other illnesses, so they cannot confirm tick fever. A sick horse should see a vet promptly, and urgent care should never wait for a lab report.

Which tests help find the parasites?

Your vet may choose one or more of these.

• The Blood Protozoa (Blood Parasite Smear) spreads a drop of blood thinly on glass, stains it and examines it under a microscope. Parasites can be seen inside the red blood cells when enough of them are present. A smear tends to work better in a sick, feverish horse, because more parasites are then in the blood.
• The Equine Piroplasmosis (Theileria equi & Babesia caballi) RT-PCR uses RT-PCR (real-time PCR), which looks for the genetic material of both parasites in a blood sample. It can pick up smaller amounts of parasite than a smear can.
• The Complete Blood Count (CBC) counts red cells, white cells and platelets, the tiny cell pieces that help blood clot. It can show anaemia, which means fewer red cells than the horse needs, but anaemia has many causes. The CBC tells your vet how the horse is coping; it does not name the parasite.

Why can a carrier horse be missed?

Some horses get over the illness yet keep a few parasites in the blood. They look healthy and may carry the parasites quietly for a long time, especially Theileria equi. A smear usually finds nothing in such a horse, because so few parasites are present. RT-PCR can find lower amounts, but a negative result still does not always rule infection out.

Why does a carrier matter? Ticks can pick up the parasites from it and pass them to other horses, and a carrier that is stressed or unwell may fall ill itself. If a horse is moving to a new yard or an event, ask your vet whether a screening test makes sense. When the picture is unclear, your vet may repeat a test later or choose a different kind of test, such as one that looks for antibodies.

How should the sample be collected?

Your vet usually takes the blood from a vein in the neck, into a tube made to keep it from clotting. A smear works better from fresh blood, so tell the lab if the horse has a fever on the day. Keep the tube cool, away from direct sun, and label it with the horse's name and the date. Tell your vet about any medicine or tick treatment the horse has had lately. The lab confirms the tube and handling when you book.

For several checks in one go, the Horse Disease Screening Pack typically groups a number of horse disease tests, including the tick fever RT-PCR. The exact list is confirmed when you book.

Read next

Young Horse Health Checks Before Training Starts lists the baseline checks that suit a young horse about to begin work, which may include a look for blood parasites. Monsoon Ticks and Fever in Madhya Pradesh Pets describes the tick season in Madhya Pradesh and the fevers that follow; it is written for pets, but the season is the same for your stable.

Testing in Bhopal

Ticks and fever do not wait, so call or WhatsApp +91 88175 01118 before the blood is drawn and the right tube will be ready. The lab is at C-200, C Sector, Shahpura, Bhopal, and collection is free anywhere in Bhopal, although for horses the vet usually takes the sample. Outside Bhopal, your vet can send the blood by courier or bus parcel. The lab confirms the method, sample needs and reporting time when you book.