Red blood cells (RBC) or erythrocytes, are small cells responsible for oxygen transportation throughout the body. They take up oxygen while circulating through the lungs and deliver it to all the other organs of the body (muscles, brain, liver, intestine, etc.).

Oxygen is indeed essential to every body cell!

To transport oxygen, RBCs are filled with a red substance which gives them their color: haemoglobin.

Anemia is a reduction in the number of RBCs in the blood. It is often detected through a blood test which reveals a decrease in RBC count, in hemoglobin concentration or in haematocrit (also called packed cell volume which is the volume occupied by the RBCs in the blood). These three values being closely linked, most of the time all three are decreased.

The first detectable sign in case of moderate anemia is poor performance. In case of severe anemia, mucous membranes (notably in the horse’s mouth) can appear paler than normal, and the horse is less willing, energetic and sturdy than usual and more quickly out of breath. If the heart rate is monitored, an abnormal increase of heart rate during exercise can be noted.

NB: Horses have a particularity which is a reserve of RBCs in their spleen which are released in case of effort or stress. This multiplies by two the number of RBCs and therefore the blood’s capacity to transport oxygen to the muscles, thus enabling the horse to run faster and escape from predators (this is an evolutionary advantage inherited from their wild ancestors)!

Causes of anemia are numerous. We usually classify them in three types:

1/ Loss of RBCs (hemorrhage)

2/ Abnormal destruction of RBCs (hemolysis)

3/ Insufficient production of RBCs

Loss of RBCs

In cases of severe injury with major blood loss, anemia is a logical result. If the blood loss is massive and sudden, it can be necessary to transfuse the horse with blood from a donor to replace the RBCs (and other important blood components) lost by the horse. If there is limited blood loss, the horse will gradually compensate for the loss by making new RBCs within a few days to a few weeks.

NB: a 500-kg horse has about 45L of blood and what might appear to be a massive blood loss to a human is not necessarily so for a horse.

A non traumatic cause of severe hemorrhaging is guttural pouch mycosis. It is a fungal infection that progressively destroys the carotid artery wall within the guttural pouch(es) and can lead to massive hemorrhaging when this weakened carotid wall is eventually torn open by the pressure of the blood. This condition can sometimes be fatal and this is why, in case of nasal bleeding, guttural pouches should always be checked by endoscopy.

Sometimes the blood loss is not visible. It happens in cases of peritoneal or thoracic haemorrhage for example. The right dorsal colitis is an ulcerative disease of the large colon due to NSAIs toxicity. It leads to protein and sometimes blood loss in the lumen of the intestine.

In case of a stomach tumor (carcinoma), chronic bleeding can lead to anemia in the long term.

In case of severe intestinal parasitism, an anemia can also occur as a result of the microtraumas made by the worms to the intestinal mucosa. This cause of anemia is rare in most countries nowadays due to deworming programs that are largely applied in all stables.

NB: Contrary to popular belief, gastric ulcers very seldom lead to anemia, and then only in extremely severe cases.

Although rare in horses, intoxication with rat poison containing antivitamin K can lead to multiple internal and/or external haemorrhages and a resulting anemia. Indeed, Vitamin K is needed for the coagulation process, and without vitamin K, the slightest trauma can lead to severe, prolonged and possibly fatal haemorrhaging.

Abnormal RBC destruction

Besides traumatic hemorrhage, the most frequent cause of anemia in horses is abnormal destruction of RBCs, which is called hemolysis. Hemolysis occurs when RBCs are weakened by an infection (parasite, bacteria or virus) or when the immune system mistakenly targets RBCs and destroys them.

A common cause of haemolytic anemia in Europe is piroplasmosis. It is due to RBC infection by a microscopic parasite (Babesia caballi or Theleria equi) transmitted by ticks. The parasite multiplies in the RBCs and weakens them until they burst, releasing the newly-formed parasites that infect other RBCs.

Equine ehrlichiosis is an infection of white blood cells by the bacteria Anaplasma phagocytophilia, transmitted by ticks. The mechanism by which RBCs are destroyed is still not completely understood.

Leptospirosis is a bacterial infection that can, in some cases, induce an haemolytic anemia. The bacteria is transmitted by rodent urine.

Equine infectious anemia is a severe contagious disease due to a viral infection transmitted by horse flies. Once infected, the horse remains infected its whole life and  can present sporadic crises of haemolytic anemia. Coggin’s test is used to diagnose this condition and infected horses must be declared because they are virus reservoirs for horseflies which become contaminated and infect other horses nearby.

Finally, Lyme disease (Borrelia burgdorferi infection) seems to be implicated in some cases of anemia in horses but the ways in which this bacteria acts are still unknown.

These 5 diseases (piroplasmosis, equine ehrlichiolis, leptospirosis, Lyme disease and equine infectious anemia) can elicit quite similar clinical signs of fever, depression, jaundice and anemia in their acute form. These symptoms are thus often referred to as “piro-like”. In their more chronic form, these diseases can lead to only a mild subclinical anemia (no or few clinical signs). They are thus often tested for by blood tests in cases of anemia with no obvious cause.

Rarely, intoxication with some plants like red maple leaf (in North America), or plants of the onion or cabbage families lead to massive and sudden oxidation of haemoglobin molecules within RBCs, and their destruction.

Finally, the immune system sometimes mistakenly targets RBCs and destroys them: this is autoimmune haemolytic anemia. Administration of some products like penicillin of trimotorpim sulfa, might, in some rare cases, trigger this reaction. An autoimmune haemolytic anemia can also occur as a complication in some bacterial infections or tumoral processes.

Inadequate production of RBCs

RBC synthesis occurs in bone marrow and necessitates several elements including iron, copper, vitamin B12 and folic acid. If one of these elements is missing, or deficient, RBC synthesis slows down and this can lead to anemia. These deficiencies, particularly iron deficiency) are frequent in humans but extremely rare in horses.

More frequently, in case of chronic infection (abcess, pneumonia, etc.), a moderate anemia occurs. It is due to a protective mechanism of the immune system: as bacteria need iron to multiply, the immune system holds back the iron in order to slow down the infection development. But as iron is also needed for RBC production, this is also slowed down.

More rarely, in cases of chronic renal insufficiency, an anemia occurs. It results from decreased production of erythropoietin (EPO) by the diseased kidneys and by insufficient elimination of toxic body waste by the kidneys. This waste accumulates in the blood stream and weakens the RBCs.

Finally, in extremely rare cases of aplastic anemia, the bone marrow can be deficient in producing RBCs.

Anemia in horses can thus have multiple causes. Some are obvious (hemorrhages) but some are far more difficult to diagnose and necessitate diagnostic procedures and/or laboratory tests. Vitamin and iron supplements will only be efficient if the horse is deficient (rare) or if it has lost a lot of RBCs (haemorrhage, piroplasmosis) and needs to replenish its stock of RBC. On the contrary, if the anemia is secondary to a chronic infection, supplementation will have no beneficial effect and might even be harmful if too significant or prolonged.

Author : DAUVILLIER Julie, Veterinary.



Privacy and Cookies Policy

Last update: March 3rd, 2021

The Vetoquinol group and the companies within it (referred to collectively in this document as “the Group”, “we” or “our”) are committed to protecting your privacy and the confidentiality of your data and we take care to protect your personal data. Please read the following information carefully. It tells you about how we collect and use your personal information and the options available to you in connection with its use.

For the purposes of this privacy and cookies policy, (the “Privacy and Cookies Policy”), the data controller is Vetoquinol SA, a company registered on the Vesoul/Gray Trade and Companies Register under number 676 250 111 and which has its registered office at sis Magny-Vernois, 70200 Lure.

This privacy and Cookies Policy applies to the products and services offered by the Group (the “Products and Services”) on our website (hereafter called the "Website") and particularly:

personal data collected on the subscription forms available on the websites of Group companies linked to the Website;

personal data collected through the contact form;

personal data collected through a request for information;

personal data which may be collected when you enter into a commercial relationship with a company in the Group.

personal data which may be collected through the use of social buttons (Facebook, Instagram, Youtube, etc);

personal data which may be collected through the installation of cookies during connection and/or when visiting the Website(s).

This Privacy and Cookies Policy applies whether you are a “Visitor” (which means you are simply looking at the Products and Services) or a “User” (which means that you have registered with the Website).

The Privacy and Cookies Policy thus governs the use of the Website however you access it.

By accessing or using the Website and providing us with information via the Site, you accept this Privacy Protection and Cookies Policy. We recommend that you regularly check the Policy as we often update and modify it.

Data that does not allow you to be identified

You can visit our Website without sending us any information that can enable you to be identified, unless you decide to become a Website User, which requires registration.

Like the majority of online services, we automatically collect certain data and information about you and/or your computer each time you visit our Website, but this does not enable you to be identified. This information includes:

The type of internet browser you use;
The type of operating system and device you use to access the Website;
Your Internet service provider’s domain name;
The web page from which you come;
The country where you live and your language;
The pages and options that you visit and access on our Website.
When you access, visit and/or use our Website we can, therefore, follow your visit and collect certain data about your use of the Products and Services and your activities on the Website, as described below in the “cookies” section.

Personal Data

In certain cases, in particular when you register, contact us or request information, you may be asked to provide personal data, such as your surname, first name, email address and telephone number (“Personal Data”).

When you contact us or ask for information by email or post, we collect the Personal Data that you voluntarily decide to disclose to us.

However, if you do not wish to disclose your Personal Data, some of the services and/or options available on the Website and/or linked to our offer of Products and Services may be unavailable to you.

We also collect Personal Data when the Website allows you to register on “My Space” or “My Account”: you will be asked to disclose Personal Data such as your surname, first name, title, year of birth, email address, country of residence, name of the employer and telephone number. We may also obtain Personal Data via your internet browser, such as your IP Address, which is a number that is automatically assigned to your computer when you use the internet.

We may also obtain Personal Data about you from other sources. For example, we may ask a third party supplier or collector to provide us with additional Personal Data about our existing clients (adding data or “data appending”), particularly Personal Data collected from your profile or your publications on a third-party social network. We may also collect Personal Data from third-party co-sponsors with whom we work or if we buy out other companies.

We may also collect Personal Data appearing on your profile for a third-party social network (particularly Facebook) if you authorise the third-party network to disclose this to us or if you put it on  line publicly. This Personal Data may be general data relating to your account (for example, name, email address, profile photo, gender, birthdate, current town/city, identifier, list of friends, etc.) and any other information or activity that you authorise the third-party social network to share with us or that you put on line publicly on your profile. We may, for example, receive all or party of your information relative to social networks when you download or interact with one of our applications on a social network site (notably Facebook). For more information on how we can obtain your information relating to social networks, please visit the Internet site of the third party social network concerned.

The Personal Data sent to the Website, either based on your consent (request for information or documentation) or based on a contract (contact form or registration on our Website to benefit from Products and Services). We may use the Personal Data you disclose to us via the Website particularly for the purposes of:

Supplying you with various Products and Services;
Creating access to “My Space” or “My Account” when the Website allows you to do so.
Providing you with documents you have requested (newsletters etc.) and inviting you to events;
Answering your questions;
Customising our offer of Products and Services and improving your browsing experience on the Website, by making it more effective and efficient;
Generally complying with the Group’s legal, regulatory accounting and tax obligations;
Informing you about Products and Services which are new or similar to those from which you already benefit and which could be of interest to you;
Processing requests and complaints related to the Website, initiated by you and/or a third party, which concern you.

Personal Data used in connection with use of the Website

We store this Personal Data only for as long as is necessary for the purpose for which we process it and in any event for the period necessary to comply with a legal or regulatory requirement.

Personal data used to send you information

Your Personal Data will be kept for as long as your subscription is live. You can bring this to an end at any time by unsubscribing, using the link shown. In any event, if you do not make contact for three years, your Personal Data will be erased.

Personal data used to send marketing offers

Your Personal Data will be kept for as long as you agree to receive our marketing offers. You can bring this to an end at any time by unsubscribing, using the link shown. In any event, if you do not make contact for three years, your Personal Data will be erased.

Personal Data used in connection with a commercial relationship

We store this Personal Data only for as long as is necessary for the purpose for which we process them, that is throughout our contractual relationship, and in any event for the period necessary to comply with a legal or regulatory requirement.

Transfer outside the European Union

When the processing of your Personal data involves a transfer to third countries outside the European Union, the transfer is to countries listed by the European Commission as providing sufficient protection for data and/or is covered by appropriate guarantees based on standard contract clauses reflecting models published by the European Commission.

When sharing of Personal Data involves transfer to the United States, recipients will have Privacy Shield certification.

The Group’s companies

We may share your Personal Data with companies in the Group. For further information on the companies in the Group, please go to

Service Providers

As part of the conduct of our business, we may transfer your Personal Data to service providers. These service providers use your Personal Data only to enable us to supply you with Products and Services. As examples, these service providers may supply IT services, be our logistics or marketing partners, our website host, or support us in data management, email distribution or analysis of information. We disclose to our service providers only the Personal Data they need to provide their services and we work with them to ensure that your Personal Data are respected and protected.

We never disclose any personal Data to these companies for their own marketing or commercial needs. However, we may disclose your Personal Data to our commercial partners only in order to provide you with our Products and Services or other products and services which may be of interest to you.

Legal Obligations

We may need to disclose Personal Data in response to a request from a regulatory authority, such as the tax authorities or CNIL (the French data protection authority), and/or a court (in response to a judgment, a court order or injunction) on request or if the law requires us to do so, or in order to protect our interests, our property and/or our security and/or those of a third party.

Unless otherwise provided in this Privacy and Cookies Policy or with your prior permission, we will not sell, market or lend Personal Data to other companies in the normal course of business. However, in the event of any restructuring of the group’s companies (acquisition, merger or partial transfer of assets) your Personal Data may be disclosed to another company, but the disclosure will then be subject to the Privacy and Cookies Policy in force.

We have a variety of security measures to prevent the loss, misappropriation or misuse of your Personal Data that you have provided on the Website. In order to guarantee the security of the data you disclose online during transmission, we use encryption, authentication, and flow analysis and we carry out security audits on the hosting environments.

A cookie is a text file placed on the device you are using to access the internet (computer, mobile phone, tablet etc.) when you use a browser to visit a website.

We place a unique identifier in the cookie and use the cookie to connect your computer to the information that we store in our database.

It contains data which allow you to be identified:

The name of the server which placed it;
A unique numeric identifier;
Possibly, an expiry date.
We use cookies to:

Recognise you when you return to our Website;
Inform you about new topics that may interest you;
Customise content that may be useful to you;
Measure the audience on the Website for marketing/commercial purposes.
Cookies do not contain any Personal Data and do not allow access to your computer.

The validity deadline to consent to receive Cookies is 13 months. At the end of this period, we will again seek your consent.

When you first visit our Website, an information banner will be displayed at the foot of the page. By continuing to browse the Website after clicking on “I accept”, you expressly consent to the Group placing the cookies you have allowed on your computer (cookies linked to targeted advertising operations, certain audience measurement cookies and social media cookies, generated in particular by sharing buttons when they collect personal data). The banner will be displayed until you continue browsing, i.e. until you make a choice. If you do not wish to receive any or all cookies, we recommend you click on "Personalise" on the banner, and follow the detailed instructions enabling you to refuse all or part of them.

You can change your internet browser settings at any time to accept, configure or refuse cookies. You will be offered a number of options: to accept each cookies, be alerted when a cookie is placed, or refuse all cookies. You also have the possibility to reconsider your choice at any time during your browsing by clicking on the button at the bottom right of your screen.

Each internet browser offers different settings for the management of cookies. They are generally shown in the browser’s help menu. If you use a browser or version different to those listed, we suggest you use the browser’s “Help” menu. Firefox, Chrome, Internet Explorer, Safari and Opera.

The Group may offer links to the websites of other companies with which it has a relationship.

We may place “hyperlinks” to other websites and applications operated by third parties on our Website. The only purpose of these links is to make browsing easier for you and to provide you with the fullest possible information. We have no control over these websites and applications. They are separate from the Group and have their own privacy policies. Consequently, the Group cannot be held liable under any circumstances, in particular in relation to the accuracy, relevance, availability or reliability of information and products and services offered on these websites, their respect for copyright, via these third party websites and applications accessible from our Website. We encourage you to review the terms and conditions and privacy policies of any third party websites and applications before using them. You should note that our Confidentiality and Cookies Policy ceases to apply when you leave our Website.

Moreover, the Group is not responsible for hypertext links to its own Website which may be included in third party websites, even if the Group has authorised the third party publisher of the website to place such a link.

Finally, the Group generally prohibits anyone from placing a hyperlink to one or more pages of its Website without its express prior consent.

If you no longer wish to receive emails from the Group informing you of events, new Products or Services, similar Products or Services, or containing other marketing communications, you only have to click on the “unsubscribe” link at the foot of every email. You will be routed directly to an unsubscribe page in which you can delete your subscription to emails.

You can log in to “My Space” or “My Account” when the Website allows you to do so. After you have logged in, you can change your profile and update your Personal Data. You are responsible for protecting your authentication data (particularly your identifiers and passwords). You also have the possibility to unsubscribe by deleting your account.

Under the legal and regulatory framework applicable to the protection of personal data and privacy, particularly the GDPR, current French legislation and the recommendations of any independent public authority established by a Member State of the European Union responsible for controlling this legal and regulatory framework, you have a right to access, rectify, object to or erase your Personal Data or limit its processing, and a right to its portability.

You also have a right to give instructions about what should be done with your Personal Data after your death.

You may write to the company Vetoquinol SA about this at any time, at the following address: Vetoquinol SA – DPO – Magny-Vernois, 70200 Lure, or by email to

In the event of a complaint, you can choose to contact the CNIL.

If you have questions or doubts concerning this Privacy and Cookies Policy, you can contact us using the form available on our Website, or by sending us a letter addressed to Vetoquinol SA – DPO – Magny-Vernois, 70200 Lure. You can also write to our Data Protection Officer by email at

This Privacy and Cookies Policy is governed by French law and, with effect from 25 May 2018, by the General Data Protection Regulation 2016/679 of 27 April 2016 (“GDPR”). Please note that this policy may change in the light of regulatory developments.