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Treatment of West Nile Encephalitis in Horses

The great difficulty in the treatment of this particular disease is that like many other viral diseases causing encephalitis, there is no specific treatment. Treatment tends to involve supportive care of the patient as well as to address any possible complications that arise from or due to the viral infection. Management in focused on controlling pain and inflammation, preventing injuries associated with ataxia or recumbency and providing nursing and supportive care to keep the animal comfortable.

Drugs of Choice for Animals with Clinical Signs

Please note: The drugs listed here are only shown as examples and descriptions of treatments used, and as such can only be administered by a veterinarian.

Treatment of horses with clinical signs has primarily focused on the administration of anti-inflammatory drugs in order to decrease the inflammatory process caused by the viral agent.

Flunixin meglumine (Banamine) (1.1 mg/kg, BID)
Flunixin is a non-steroidal anti-inflammatory drug that has been used early in the course of the disease.
Flunixin has been shown to decrease the severity of muscle tremors and fasciculations within a few hours of administration.

Dexamethasone (0.05-1.0 mg/kg, IV, SID)
Dexamethasone is a steroidal drug that is used in the treatment of recumbent horses and is considered more aggressive than treating the horse with only Flunixin.

Mannitol (0.25-2.0 mg/kg, IV)
Mannitol is a sugar alcohol in IV solution that works as an osmotic diuretic to decrease edema present in the brain, therefore reducing intercranial pressure.
Mannitol is also administered with Dexamethasone in the aggressive treatment used in recumbent horses.

Dimethyl Sulfoxide (DMSO)
DMSO is another NSAID used to decrease inflammation.

Detomidine (Dormosedan) (0.02-0.04 mg/kg, IV or IM)
Detomidine is useful in sedating horses which tend to thrash, and may decrease the incidence of injury.
Detomidine is effective for long term tranquilization.

Acepromazine (Low dose 0.02 mg/kg IV or 0.05 mg/kg IM)
Low doses of Acepromazine provide relief from anxiety in horses that are either standing or recumbent.

Diazepam and Butorphanol
It is important to note that Diazepam and Butorphanol have been found to increase anxiety and tremors and should therefore be AVOIDED.

Supportive Therapy

In horses which are recumbent, and sling and hoist may be used to assist these animals in standing. Slinging recumbent horses has also been found to decrease pulmonary and traumatic sequelae, as well as to maintain the strength of the animal.

In horses that have urinary incontinence (especially male horses), catheterization of the urinary bladder may be necessary until clinical signs are reduced and urinary continence returns.

In animals which are unable to eat or drink, intravenous fluids and nutritional support may be necessary.
Broad spectrum antibiotics may be necessary to treat self-inflicted wounds, cellulitis, and secondary pneumonia.

horsesling 




References

Alberta Government Agriculture & Food: West Nile Virus.
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex5455

The Merck Veterinary Manual: West Nile Encephalitis.
 http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/102700.htm


Image References

UC Davis: 

http://www.vmth.ucdavis.edu/home/VERT/LART/images/horse_sling.jpg

Maryland Department of Health and Mental Hygiene: http://edcp.org/html/wn.html


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