What is equine piroplasmosis and how is it treated?

A few days ago, Andrea contacted us to tell us about her personal case and ask for recommendation.

In this case, Andrea told us about her PREcolt, which had a blood test whose resultspointed that it could have equine piroplasmosis.

equine piroplasmosis

Juan Carlos Calvo Barrios

Because of its logical concern and its lack of knowledge of the disease, she asked for advice and information.

Well, to answer Andrea and those that may be in the same situation, today we will talk about this disease: what is equine piroplasmosis and how it is treated? It is a very tricky and contagious disease that we will discuss here in depth.

We are going to start by determining this type of ailment: What is equine piroplasmosis? Equine piroplasmosis, also known as equine babesiosis, is one of the most common horse diseases.

It is an infection that affects horses and other animals such as mules or donkeys, produced by protozoa(Babesia caballi or Theileria equi)- also known as Babesiaequi- and  transmitted by ticks.

One of the biggest problems of equine piroplasmosis is its difficult detection. So, the horse does not always present the same symptoms to determine this disease. But not only that, there is not a vaccine against piroplasmosis, although there are treatments that mitigate the effects of the infection.

A horse suffering from equine piroplasmosis can have different symptoms such as gradual loss of weight, lack of appetite, acute fever and even anemia, to give some examples.

This disease is one of the problems in the export and import of horses, since it means a serious risk of transmission to other equines.

Seeing the severity of this disease, the first thing we have to do is to stop and think how our horse has been infected by these parasites.

How is piroplasmosis transmitted?

As discussed above, equine piroplasmosis is produced by two protozoa called Babesia caballi and Theileria equi. Ticks carry these two parasites and infect the horse through their bites.

These types of parasites are found in tropical and semitropical countries, including Spain, where some studies have stipulated that 30% of horses in Spain could be infected by these parasites.

horse equine piroplasmosis


Moreover, it is estimated that this disease is present in 90% of countries where there are horses, being the only endemic countries of these protozoa Australia, Japan, England, United States, Ireland and Canada. Therefore, these countries do very exhaustive controls of the horses that can come from populations where the disease still exists.

The tick bite causes a blood infection of the horse, destroyingthe red blood cells and causing anemia.

Depending on the species of parasite that infects the horse, the disease can be more or less severe.

In the case that the animal is infected by the Babesia caballi, it is estimated that around 1% of the red blood cells of the horse will be affected by the parasite that may remain in the body of the horse from one to four years.

More serious would be if the animal is infected by theTheileria equi, affecting a fifth of the red cells of the horse and remainingin the body for the rest of its life.

Therefore, from Equusline we always recommend you to make revisions to your horses. Remember that it is a contagious disease and could affect other nearby animals.


How to detect equine piroplasmosis?

The problem to identify a carrier horse of equine piroplasmosis is that the animal may suffer different symptoms. We have already mentioned that, along with acute fever, there may be anemia, lack of appetite or loss of weight. But there may be many more symptoms. The horse can suffer exhaustion, jaundice, enlarged spleen and an increase in heart or respiratory pulsations. It can also suffer colic, diarrhea or inflammation of the legs and the disease can even cause sudden death.

Another problem to find out if a horse is a carrier of these parasites is that the horse can overcome these symptoms, but it can be a carrier for a while, or a permanent carrier, as we have seen, and get sick again in the future. This risk affects not only the animal itself, but also other equines if the appropriate measures are not taken.

stables horses piroplasmosis

Jimmy Baikovicius

To do this, there are two ways to tell if a horse is equine piroplasmosis carrier. The first is by identifying the parasite, while the second is through serological tests.

Identification of parasitic agents

One technique for identifying parasitic agents is the visualization of parasites in blood staining.

Still, through the microscopic examination it can be very difficult to detect the infectious parasites, due to the reduced level of parasitemia transmitted. This happens especially with the Babesia caballi infection. Remember that this parasite affects 1% of the blood cells of the horse. In these cases, the parasite may be detected by the technique of blood smear.

babesia caballi

Inside AE

By this analysis, we can detect the presence of the Babesia caballi in horses when we appreciate pairs ofmerozoites attached by their rear end. When it comes to the Theileria equi, it usually has four parasites attached in tetrad.

Serological tests

If the identification of parasitic agents offers confusing results, the serological tests on the horse can resolve the doubts. In fact, if you intend to export horses, the international trade requested the study of the horses sera and thus detect the presence of specific antibodies, with two very specific tests: the indirect immunofluorescent assay (IFA) and the enzyme-linked immunosorbent assay (ELISA ).

theileria equi


The ELISA test can help us detect antibodies that act against both parasites. However, as the antibodies may have cross reactions to both parasites, it cannot determine if the infection is caused by the Babesia caballi or by the Theileria equi.

In this regard, the IFA test can serve to differentiate between infections of Babesia caballi and Theileria equi.

Treatment in horses with piroplasmosis

Despite the advances in veterinary treatments, there is currently no vaccine for infected horses.

Of course, there are treatments that can help alleviate the effects andreduce the problems arising from such infection and the possible contagion.

One treatment that has helped to eliminate the presence of parasites from a horse,even if it remains a carrier- is the Imidocarb Dipropionate. This medicine has historically had serious side effects for the animal, including diarrhea, intense colic and even liver and kidney toxicity.

In 2012, a study of the Imidocarb dipropionate treatment, carried out by Janina Kutcha (Aberdeen, Scotland), determined the best solution for this medicine. This analysis was performed using a saline solution, intravenous, atropine and glycopyrrolate, determining that the latter solution was giving fewer symptoms of colic and diarrhea. Thus, the Imidocarb dipropionate with glycopyrrolate solution (I / G) is, today, the best treatment to alleviate the disease and maintain, in a certain way, the welfare of the horse.

piroplasmosis treatment

To prevent the contagion of equine piroplasmosis within a zone free of this infection, the first measure to take is to quarantine the infected horse and avoid contact with other equine animals. Similarly, the zone must be fumigated several times with acaricides, removing the vegetation and the presence of ticks must be checked daily. Also the feces of the horses may be removed because the ticks may be present in the stools themselves.

As we have seen throughout the post, equine piroplasmosis can be a big problem for a horse and its possible contagion, so you must take all the appropriate measures to ensure that it does not spread.

If you have the same questions Andrea had, we hope that all this information has been helpful.

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2 Comments. Leave new

As a horse owner, we should keep watch our horses and other horses that they may encounter. I cant afford to let my horse get the same parasites. aside from its costly, the risk of loosing a horse is there.

Graham Davison
15 May, 2018 3:13 pm

A very informative article, thank you. One of our 4 donkeys in Lot et Garonne, France has just been diagnosed with piroplasmosis. Treatment starts tomorrow. Nothing has been mentioned about quarantine, though it makes sense to me even if it is going to be very difficult practically given the donkey’s need for close company. What drugs should we expect our vet to use and what treatment programme should she follow?


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