Fever in Horses: Causes, Symptoms, and What You Can Do
Fever in horses is more than just a raised temperature – it’s an important sign that your horse’s body is fighting off illness or stress. Knowing how to spot early symptoms, measure temperature accurately, and take the right steps can make all the difference. In this guide, you’ll learn everything about the normal temperature range, potential causes of fever, when to call a vet, and how to support your horse’s recovery. From viral infections like West Nile Fever to tips on immune boosting and stable hygiene – we cover it all.
Table of Contents
Fever in Horses
Fever is an elevated body temperature that signals an immune response in the horse’s body. It is a natural defense mechanism used to fight off pathogens such as bacteria or viruses. In medical terms, a horse is considered to have a fever when its body temperature rises above 38.5 °C. Temperatures below this threshold are classified as elevated but not necessarily pathological.
Normal Body Temperature in Horses
- Adult horse: 37.5–38.2 °C
- Foal: up to approximately 38.5 °C
When Is It Considered a Fever?
- From 38.5 °C: considered a fever
- From 39.5 °C: considered high
- From 40 °C: can be dangerous and should be evaluated by a veterinarian
How to Take a Horse’s Temperature
To reliably determine whether your horse has a fever, you need to measure its temperature correctly. The only dependable method is rectal measurement using a digital thermometer designed for horses.
How to Take a Horse’s Temperature – Step by Step
- Use a digital thermometer for horses – ideally one with a flexible tip.
- Apply a small amount of lubricant to the thermometer to make insertion easier.
- Gently insert the thermometer into your horse’s rectum – about 5 to 10 cm deep.
- Hold the tail securely to prevent your horse from kicking.
- Stay calm and speak softly to your horse to avoid startling it.
- Wait for the thermometer’s beep – the measurement takes just a few seconds.
- Thoroughly disinfect the thermometer after use to prevent the spread of germs.
The temperature you measure provides valuable insights into your horse’s health – especially if you check it regularly and track any changes over time.
Fever Symptoms in Horses
Fever in horses often begins with subtle changes. Some horses may still appear normal with only a slightly elevated temperature, while others show clear signs early on. It’s crucial to recognize and correctly interpret the typical symptoms of fever in horses.
Common signs include:
- Lethargy or general apathy
- Loss of appetite or reduced water intake
- Increased respiratory rate or elevated pulse
- Swollen lymph nodes or legs
- Muscle tremors and sweating without exertion
- Reluctance to move or resistance when being led
- Warm ears or hooves – often an early warning sign
- Dull, lackluster coat – a sign of internal strain
The more of these symptoms appear simultaneously, the more likely it is that your horse is experiencing a serious underlying issue.
Fever in Horses : Causes
Fever is not a disease itself, but a symptom. It indicates that the body is reacting to a disruption – such as pathogens, inflammation, or external stressors. The causes of fever in horses are varied and can be broadly divided into infectious and non-infectious categories.
Infectious causes of fever in horses:
- Viral infections: e.g., influenza, herpesviruses (EHV-1/EHV-4), or equine viral arteritis (EVA)
- Bacterial infections: e.g., strangles, pneumonia, wound infections
- Parasitic infestations: rare, but possible in severe cases or with systemic reactions
There are several well-known equine diseases in which fever or an elevated temperature is a prominent symptom.
This table can help you quickly consider potential causes when your horse has a fever – but remember: Always consult a veterinarian!
Non-infectious causes of fever in horses:
- Post-vaccination fever: temporary and usually harmless (typically 1–2 days after vaccination)
- Injuries and inflammation: e.g., after surgery or internal tissue trauma
- Allergic and toxic reactions: e.g., to medications, certain plants, or environmental toxins
- Stress responses: very rare, but possible under extreme physical or psychological strain
A special case is unexplained fever in horses. This occurs when, despite thorough diagnostic efforts, no clear cause is immediately found. In such instances, the condition is referred to as fever of unknown origin – and often requires advanced laboratory testing and imaging to identify the source.
West Nile Fever in Horses: Recognizing a Dangerous Viral Infection
West Nile fever is a serious viral disease in horses, transmitted by mosquitoes. In addition to fever, it can cause neurological symptoms such as tremors, coordination problems, or weakness. The illness doesn’t always present with typical signs – making early detection especially important.
Symptoms of West Nile Fever in Horses:
- Sudden, high fever
- Muscle weakness or tremors
- Ataxia (loss of coordination)
- Sensitivity to light, irritability, or apathy
- In severe cases: paralysis
What to Do If Your Horse Has a Fever
If you notice a fever in your horse, it’s important to stay calm and act thoughtfully. Not every elevated temperature requires immediate veterinary treatment – but it should always be taken seriously and monitored closely.
Here’s how to respond properly if your horse has a fever:
- Check the temperature regularly – ideally every 4 to 6 hours
- Keep a fever log: record the temperature, time, and any observed symptoms
- Watch for behavioral changes: Is your horse eating? Does it seem dull or restless?
- Provide fresh water and ensure your horse is drinking enough
- Minimize stress and keep the environment calm
- Keep your horse warm – but do not blanket it if it's already sweating
If the temperature remains elevated for more than 24 hours or rises above 39.5 °C, you should definitely call a veterinarian. In such cases, a thorough diagnosis and possibly antipyretic medication or other treatments may be necessary.
Fieber senken Pferd: Wann Medikamente wirklich nötig sind
Ein weitverbreitetes Missverständnis ist, dass man Fieber beim Pferd sofort mit Medikamenten behandeln muss. Doch Fieber ist zunächst eine sinnvolle Reaktion des Immunsystems, die dem Körper hilft, Krankheitserreger zu bekämpfen.
Wann braucht dein Pferd einen Fiebersenker?
- Bei einer Temperatur über 39,5 °C
- Wenn das Fieber länger als 24–48 Stunden anhält
- Wenn weitere starke Symptome auftreten (z. B. Bewegungsunlust, Atemnot, neurologische Auffälligkeiten)
- Wenn dein Pferd älter, sehr jung oder gesundheitlich vorbelastet ist
In solchen Fällen kann der Tierarzt nicht-steroidale Antiphlogistika wie Flunixin, Phenylbutazon oder auch Metacam einsetzen. Diese Mittel wirken entzündungshemmend, schmerzstillend und helfen, das Fieber beim Pferd zu senken.
Protect your Horse! Fever and Stable Management
If your horse is suffering from an infectious disease, it’s essential to rule out or contain any contagious illness. This means:
- Isolate the affected horse from the rest of the herd.
- Avoid any contact with other horses – including shared buckets, water troughs, or handling equipment.
- Thoroughly disinfect all tack and equipment, such as halters, grooming tools, and saddle pads.
- Wear protective clothing or change clothes before handling healthy horses.
- Monitor your horse’s temperature regularly – and also keep an eye on the rest of the horses in the stable.
Outbreaks of diseases like equine herpesvirus or influenza can spread quickly in a barn – and maintaining strict hygiene is your best line of defense.
➡️ Must Watch: Learn all about Equine Herpes Virus (EHV), the differences between EHV-1 and EHV-4, common symptoms like respiratory issues, abortions, and neurological signs, plus how the virus spreads—and why vaccination is a smart preventive step for horse owners.
The Role of the Immune System – and How to Strengthen It
A strong immune system is the best protection against disease – and can help prevent fever from developing in the first place. Many infections that lead to elevated body temperature in horses tend to affect animals with weakened defenses.
Here’s how you can support your horse’s immune system:
- Feed high-quality hay in sufficient quantity
- Ensure proper intake of zinc, selenium, and vitamin E – essential micronutrients for immune defense
- Provide plenty of fresh air and regular exercise
- Keep your horse in a low-stress, species-appropriate environment
- Establish consistent routines and reduce environmental stress like noise or frequent changes
- Maintain regular deworming and vaccination schedules
Especially during times of increased infection risk – such as spring or when new horses are introduced – a stable body temperature is a key indicator of your horse’s health. Regular monitoring helps detect changes early.
For sensitive or frequently ill horses, immune-supporting feed supplements may be beneficial.
Conclusion: Take Fever in Horses Seriously
Fever is an important warning sign – not a reason to panic, but certainly not something to ignore. A persistently elevated temperature indicates that your horse’s body is fighting stress – whether due to infection, inflammation, or another issue.
Knowing how to recognize fever, measure temperature correctly, and interpret changes gives you the tools to protect your horse’s health and act quickly when needed.
- Normal horse temperature: 37.5 to 38.2 °C
- Fever starts at: 38.5 °C – critical above 39.5 °C
- Key measures: frequent temperature checks, good stable management, and strong immune defense
Especially during stressful periods like stable changes, intense training, or after vaccinations, keep an eye on your horse’s temperature – it’s one of the earliest indicators of illness.
Keeping a fever log, maintaining open communication with your veterinarian, and taking preventive steps will help you respond effectively when your horse needs care.
FAQ – Common Questions About Fever in Horses
What medication can be used for fever in horses?
Fever-reducing medications like flunixin, phenylbutazone, or Metacam must be administered by a veterinarian. These drugs have anti-inflammatory effects and help lower body temperature. Never treat your horse without a clear diagnosis – this could mask symptoms and cause harm.
When is a horse considered to have low body temperature?
If a horse’s temperature drops below 37 °C, it is considered hypothermia. This can signal circulatory problems, shock, or severe exhaustion and is just as serious as fever.
How can I reduce a horse’s fever?
Provide rest, minimize stress, offer fresh water, and keep your horse warm without overheating. Fever-reducing medications should only be given by a vet – never attempt to medicate on your own.
At what temperature is a horse considered to have a fever?
Fever in horses starts at 38.5 °C. Normal temperature ranges from 37.5 to 38.2 °C. Values above that should be monitored closely.
Is 40 degrees Celsius dangerous for a horse?
Yes. A temperature of 40 °C or higher can lead to organ damage or circulatory collapse. A veterinarian must be contacted immediately, especially if symptoms like apathy or breathing difficulties are present.
What is considered a high fever in horses?
A temperature of 39.5 °C or more is classified as high fever. At this point, veterinary evaluation is essential, especially if it persists or occurs alongside other symptoms.
What can cause fever in horses?
Most commonly: infections (viruses, bacteria), vaccine reactions, inflammation, parasites, or poisoning. Equine herpesvirus and influenza are frequent culprits.
When does fever become dangerous in horses?
If it exceeds 39.5 °C, lasts longer than 24–48 hours, or occurs with symptoms like colic, weakness, or breathing issues, it’s critical. Immediate veterinary attention is required.
How do you check a horse for fever?
By measuring rectally with a digital thermometer. Ensure calm handling, hygiene, and safety. This is the only reliable method for accurate results.
How does fever present itself in horses?
Common signs include lethargy, loss of appetite, muscle tremors, swollen lymph nodes, rapid breathing, warm hooves or ears, and a dull coat.
Can stress cause fever in horses?
In rare cases, severe stress can temporarily elevate body temperature. However, fever is usually a sign of an underlying illness.
Does a horse always have a fever during colic?
Not necessarily. Fever is not typical in colic cases. If present, it may point to an underlying inflammation or abdominal infection and should be evaluated promptly.
At what temperature is it officially considered a fever in horses?
Fever starts at 38.5 °C. The normal range is 37.5–38.2 °C. Temperatures over 39 °C usually require treatment.
How do you take a horse’s temperature?
With a digital rectal thermometer. The process takes only a few seconds and should be done calmly and carefully – ideally while holding the tail.
How does a horse behave when it has a fever?
It often appears dull, eats less, is reluctant to move, sweats without exertion, and may show increased breathing or pulse. The coat may also look dull.
What is considered a fever in foals?
Foals have a slightly higher normal range (up to 38.5 °C). Fever starts at around 39 °C. Even mild increases should prompt quick action.
What is a normal evening temperature for a horse?
Temperatures may rise slightly in the evening. Values up to 38.3 °C are within the normal range. Still, regular measurements at the same time of day ensure reliable comparisons.
How high can a horse’s fever be?
Up to 39.0 °C is considered mild fever, up to 39.5 °C moderate. Above that is critical – 40 °C or higher requires urgent veterinary care.
When should a vet be called for a horse with fever?
If the fever rises above 39.5 °C, lasts longer than 24 hours, or is accompanied by significant symptoms. Also seek veterinary advice if the cause of the fever is unclear.