What causes Encephalitis or Acute Encephalitis Syndrome (AES)?
The most common cause of Acute Encephalitis Syndrome (AES) in horses is thought to be viral infection, although it is believed that it can also be brought on by bacterial, protozoan or fungal causes. Some researchers have designated AES as a group of conditions of that affect the brain and may be caused by a wide range of viruses, bacteria, fungi, spirochetes, parasites, chemicals and toxins.
What is AES, and what causes it?
Acute Encephalitis Syndrome is a condition in which the outer covering of the brain becomes inflamed due to an infection; the infection exerts pressure on the brain, leading to headaches, fever, confusion and dizziness. In some cases, AES can lead to permanent brain damage and coma, convulsions, seizures and hallucinations.
Cases of AES are frequently recognized as having Eastern equine encephalitis, with the Eastern equine encephalitis virus (EEEV) as a causative agent. Eastern Equine Encephalitis (EEE) virus tends to occur in outbreak form. First identified in mosquitoes in Louisiana in 1951, the disease is transmitted to horses by mosquitoes that have fed on infected wild birds.1
The incubation period for Eastern equine encephalitis virus (EEEV) disease (the time from infected mosquito bite to onset of illness) ranges from 4 to 10 days. EEEV infection can result in one of two types of illness, systemic or encephalitic (involving swelling of the brain, referred to below as EEE). The type of illness will depend on the age of the person and other host factors. It is possible that some people who become infected with EEEV may be asymptomatic (will not develop any symptoms).2
Indicators typically include symptoms such as fever, with subsequent deepening symptoms including confusion, muscle weakness and seizures.
AES attacks the central nervous system; onset of clinical symptoms are abrupt and infected horses often die within three days. Symptoms typically include fever, lethargy, muscle twitching in head, neck, shoulder and flanks, staggering gait and recumbency. The fatality rate can be 90% or higher, and an animal that survives the disease may have brain damage.
Although there is no specific treatment for AES, available treatment depends on the severity of the infection. Medications to relieve symptoms for mild infections and antiviral drugs can clear certain infections caused by viruses.
The best information suggests that annual vaccination of all horses and other equines against EEEV is indicated. Horses vaccinated for the first time must receive an injection of EEE-WEE combined vaccine, followed by a second dose three to four weeks later.1 Additionally, some veterinarians recommend that horses should be taken in at times when the mosquito population is highest.
Toltrazuril may be used to treat EPM (equine protozoal myeloencephalitis), which causes a multitude of effects that manifest in a variety of the above symptoms. It is often combined with other compounds to provide synergistic effects, such as Toltrazuril 250 mg/ml / DMSO 10% and Toltrazuril 250 mg/ml / Folic Acid 5 mg/ml / Vitamin E 300 IU/30 ml.
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services Nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.