Epizootic hemorrhagic disease
Epizootic hemorrhagic disease (MHE) is a serious viral infection that mainly affects wild deer, including deer. It is caused by a virus transmitted by small biting insects called culicoides. The disease causes damage to blood vessels, leadi...
What is it?
Epizootic hemorrhagic disease (MHE) is a serious viral infection that mainly affects wild deer, including deer. It is caused by a virus transmitted by small biting insects called culicoides. The disease causes damage to blood vessels, leading to internal bleeding and shock which can lead to death within a few days. It does not affect humans.
Key point
Disease that can cause high and rapid mortality during epizootic episodes; any suspicion should be reported to the competent veterinary authorities.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Affected deer present with high fever, marked depression and a sudden loss of appetite.
Swelling of the head, neck or tongue is often observed, as well as excessive salivation due to ulcers in the mouth.
Breathing may become difficult and rapid.
Lameness sometimes appears due to lesions in the hooves or joints.
In severe forms, the animal remains lying down, unable to get up, with pale mucous membranes and sometimes blood in the stools.
Death can occur very quickly, sometimes in less than 24 to 48 hours, without visible warning signs.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by a virus of the Orbivirus genus, close to that of bluetongue. There are several serotypes of the MHE virus.
The hot and humid periods of late summer and autumn favor the proliferation of culicoides and therefore episodes of disease.
Areas with the presence of stagnant water points or wetlands are more at risk.
Deer living in high-density parks or reserves may be more exposed due to the increased presence of insect vectors.
Transmission
The virus is transmitted only by the bite of small midges of the Culicoides genus. There is no direct transmission between animals, nor contact necessary for spread.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is based on clinical observation associated with specific laboratory analyzes carried out by a veterinarian or an official veterinary laboratory. Blood or tissue samples allow the virus to be identified using specialized tests. As the clinical signs resemble other hemorrhagic diseases, laboratory confirmation is essential.
Treatment
There is no specific treatment for the virus itself. Veterinary care aims to support the affected animal: fluids to combat dehydration, anti-inflammatories and supportive care depending on the clinical condition. Severely affected animals often have a very poor prognosis despite treatment.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no commonly available vaccine for this disease in deer.
Prevention is mainly based on limiting exposure to biting insects: reduction of stagnant wetlands, use of repellents if possible on animals in captivity, and increased surveillance during risky periods (end of summer, autumn).
Epidemiological surveillance of wild populations allows early detection of outbreaks.
Possible complications
Complications include severe internal bleeding, circulatory shock, significant dehydration and bacterial superinfections of oral ulcers. Mortality can be high during epizootic episodes affecting wild populations.
When to see a veterinarian
A deer presents with a sudden fever with marked depression.
Abnormal swelling of the head, neck, or tongue is observed.
The animal salivates excessively or refuses to eat.
Lameness appears suddenly without obvious trauma.
The animal remains lying down and is no longer able to get up.
Several animals from the same group show similar signs at the same time.
Prognosis
The prognosis varies depending on the severity of the infection. Some animals have a mild form and recover spontaneously. Others, suffering from acute or peracute forms, quickly progress to death despite treatment. Survival depends on how early treatment is received and the general condition of the animal.
Frequently asked questions
Can epizootic hemorrhagic disease be transmitted to humans?
No, this disease is not transmissible to humans. It only affects certain animals, mainly wild deer such as deer.
Can deer be vaccinated against this disease?
There is no widely available vaccine for this disease in deer. Prevention is essentially based on the fight against insect vectors.
How does a deer get this disease?
Deer are infected only by the bite of small midges called culicoides, which carry the virus. There is no direct contagion between animals.
What should you do if several deer in the same park appear sick at the same time?
You should quickly contact a veterinarian or official health services, as this may indicate an epizootic outbreak requiring a declaration and reinforced surveillance.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
CDC — Centers for Disease Control and Prevention
Content reviewed by the TunisieVet editorial team · Updated 15 September 2026
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