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11 June 2020

Theileria equi (originally named Babesia caballi. These parasites are transmitted by ticks, Rhicephalus (Red Legged Tick). Both these species of ticks are common in the Natal Midlands area. The Blue Tick is a single host tick and reasonably easy to control while the Red Legged Tick is a two host tick and poses more of a problem.

When the tick bites a horse the parasite enters the blood stream, then infects and multiplies within the red blood cells. This invasion of the red blood cells causes them to rupture resulting in anaemia and release of toxins into the body.

Imported horses and horses moved to a new area are more susceptible to the disease than local horses and relapses may occur in all groups.

B. equi is generally more severe than that caused by caballi and has a higher mortality rate.

Foals born with Piroplasmosis acquired whileinutero are weak and collapsed at birth, they are unable to suckle and their mucous membranes are icteric with small petechie (tiny blood blisters) and generally die. (Careful not to confuse this with Neonatal Haemolytic Isoerythrolysis).


In order to kill the parasite in the blood stream Imidocarb (Forray/Imazol) is the most commonly used drug. There can be acute colic-like side effects so split the dose or consult your Vet for additional treatment. Diminazene (Berenil, Dizene) is another drug that is registered, but causes severe local reactions and is not recommended. Supportive treatment with Vitamins with Iron, Hepatic stimulants, fluids and even blood transfusions are part of the overall treatment for Piroplasmosis. These make the horse feel better, improves appetite and assists in the regeneration of red blood cells resulting in a quicker, more effective recovery.

Drugs commonly used to drop the temperature may be harmful to the kidneys and should used with caution or only when fluids are administered.