Western Equine Encephalitis Treatment & Management

  • Author: Mohan Nandalur, MD; Chief Editor: Burke A Cunha, MD  more...
 
Updated: Feb 29, 2016
 

Approach Considerations

Focus initial medical care on a prompt diagnosis, with differentiation from other potentially treatable causes of the patient's symptoms. Because the disease mimics other encephalitides and meningitis or meningoencephalitis, implement prompt drug therapy. The physician should probably begin with triple antibiotic therapy for generalized bacterial coverage and begin acyclovir (10 mg/kg) to empirically treat herpes simplex virus.

As with all critically ill patients, take care to stabilize the patient first. Because of the similarity in presentation between encephalitis and meningitis, implement broad-spectrum antibiotics and an antiviral agent in these patients until more definitive tests are available.

Like all alphaviruses, Western equine encephalitis (WEE) has no specific treatment. Management remains focused primarily on supportive and preventive measures. Treatment also varies based on the stage of the disease. In the early stages of the viral prodrome, diagnosis is essential. Prophylactic use of steroids, ribavirin, or anticonvulsants in this early viremic stage has not been studied.

Once the patient is comatose, perform obvious measures (eg, respiratory maintenance with ventilator support). Ideally, maintain early awareness regarding whether the patient will require transfer to an appropriate level of care (eg, a critical care unit). In addition, appropriately maintain the patient's nutritional status.

Pharmacologic therapy consists primarily of antipyretics, analgesics, and anticonvulsants.

Surgical treatments for this disease are not available, except for appropriate neurologic procedures directed at a large CNS bleed or the consequences of markedly elevated CNS pressure. Rarely, brain biopsy may be performed.

Although no current medical therapies are available for WEE, research has revealed some possibilities, as follows:

  • Viral envelope proteins are capable of being functionally expressed in culture and in the future may lead to a subunit vaccine for Wee
  • An antibody with appropriate specificity attenuates the intracellular processes necessary for viral replication in animal models
  • Cytotoxic T cells play an important part in recovery from CNS lesions in mice
  • Nucleoside analogs (eg, ribavirin) have in vitro activity, but no clinical application is yet apparent
  • Additionally, a repertoire of mouse monoclonal antibodies (MAbs) against WEE currently exists; these are currently not in clinical practice and may eventually become a form of immunodetection or immunotherapy.

Whether these therapies can be productive in humans remains to be elucidated.

The patient must be transferred to the ICU when appropriate.

Many issues are also secondary to the high mortality rate of the disease.

Social work services and other appropriate hospital services should be available to the patients' families.

See the following for more information:

Treatment of SIADH

If the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is present, treat it accordingly.

Dietary considerations

Undertake appropriate nutritional measures based on the patient's mental status.

Follow-up care and monitoring

Because of the potential for high neurologic morbidity, coordinated care and quality follow-up care must be arranged. Patients often require speech therapy, physical therapy, neurodiagnostic follow-up, and potential audiologic testing.

The primary care physician must also be aware of subtle changes in behavior, intelligence, and motor skills.

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Deterrence and Prevention

Bird and mosquito monitoring

The potential exists for monitoring the sources of Western equine encephalitis (WEE) infection by assessing the serology of antibodies to WEE in certain wild birds or sentinel birds.

The virus may also be recovered from adult mosquitoes and may provide an opportunity for screening in possible vector habitats. Current screening is ongoing for other arthropod-borne illnesses, such as West Nile encephalitis and EEE.

Areas where the disease is endemic, where the virus has been isolated, or areas at high risk should have the vector mosquito population controlled.

An early outbreak of WEE should cause potential assessment for and deterrence of an epidemic. This should become easier for environmental screening agencies in the future with newly developed techniques, such as an indirect enzyme immunoassay, which has been developed to screen wild birds for antibodies against WEE.[7, 8]

Public information

Warn individuals who are at high risk in high-risk areas to take the necessary precautions against WEE. This includes the use of appropriate clothing (eg, long pants, long-sleeved shirts) and mosquito repellant and the avoidance of areas with high mosquito activity (especially during times of day when mosquitoes are most active).

Mosquito netting at nighttime also can be used if appropriate.

Permethrin 5% cream (marketed for scabies prevention) has been found to deter arthropod bites for up to a week. Treated skin is not an effective repellant, but it often causes the insect to die before biting. A permethrin rinse has also been used on clothing and has been proven effective for prevention.[9]

Vaccination

Currently, a vaccine for WEE is available, but it is not in widespread use and may not be effective against certain antigenic variants. The current use for the vaccine is for environmental workers with high exposure risk.

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Consultations

Consultations are primarily obtained for supportive measures.

Consultation with an infectious disease specialist is particularly relevant if the physician is unable to determine the etiology of the encephalitis or meningoencephalitis. The most important contribution is likely to be the ability to rapidly ascertain a potentially reversible cause of the patient's symptoms.

Neurologists also may provide early insightful information and aid in the diagnostics (eg, EEG) and treatment of complications.

If a general practitioner treats the patient, a critical care consultant is valuable to coordinate intensive care unit (ICU) treatment.

Consult a neurosurgeon only if needed for the treatment of complications.

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Contributor Information and Disclosures
Author

Mohan Nandalur, MD Staff Physician, Department of Internal Medicine, Section of Cardiovascular Medicine, Washington Hospital Center

Mohan Nandalur, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, American College of Physicians-American Society of Internal Medicine, Phi Beta Kappa

Disclosure: Nothing to disclose.

Coauthor(s)

Andrew W Urban, MD Chief, Section of Infectious Diseases, Middleton Memorial Veterans Hospital; Clinical Assistant Professor, Department of Internal Medicine, University of Wisconsin at Madison School of Medicine and Public Health

Andrew W Urban, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John L Brusch, MD, FACP Assistant Professor of Medicine, Harvard Medical School; Consulting Staff, Department of Medicine and Infectious Disease Service, Cambridge Health Alliance

John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Acknowledgements

Kenneth C Earhart, MD Deputy Head, Disease Surveillance Program, United States Naval Medical Research Unit #3

Kenneth C Earhart, MD is a member of the following medical societies: American College of Physicians, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and Undersea and Hyperbaric Medical Society

Disclosure: Nothing to disclose.

References
  1. Jose J, Snyder JE, Kuhn RJ. A structural and functional perspective of alphavirus replication and assembly. Future Microbiol. 2009 Sep. 4:837-56. [Medline]. [Full Text].

  2. Sindac JA, Barraza SJ, Dobry CJ, Xiang J, Blakely PK, Irani DN, et al. Optimization of Novel Indole-2-carboxamide Inhibitors of Neurotropic Alphavirus Replication. J Med Chem. 2013 Nov 12. [Medline].

  3. Netolitzky DJ, Schmaltz FL, Parker MD. Complete genomic RNA sequence of western equine encephalitis virus and expression of the structural genes. J Gen Virol. 2000 Jan. 81 Pt 1:151-9. [Medline].

  4. Bianchi TI, Aviles G, Monath TP. Western equine encephalomyelitis: virulence markers and their epidemiologic significance. Am J Trop Med Hyg. 1993 Sep. 49(3):322-8. [Medline].

  5. Sellers RF, Maarouf AR. Weather factors in the prediction of western equine encephalitis epidemics in Manitoba. Epidemiol Infect. 1993 Oct. 111(2):373-90. [Medline].

  6. Johnson AJ, Martin DA, Karabatsos N. Detection of anti-arboviral immunoglobulin G by using a monoclonal antibody-based capture enzyme-linked immunosorbent assay. J Clin Microbiol. 2000 May. 38(5):1827-31. [Medline].

  7. Chiles RE, Reisen WK. A new enzyme immunoassay to detect antibodies to arboviruses in the blood of wild birds. J Vector Ecol. 1998 Dec. 23(2):123-35. [Medline].

  8. Wang Z, Zhang X, Li C, Zhang Y, Xing D, Wu Y, et al. Vector competence of five common mosquito species in the People's Republic of China for Western equine encephalitis virus. Vector Borne Zoonotic Dis. 2012 Jul. 12(7):605-8. [Medline].

  9. Elgart ML. Medical pearl: permethrin can prevent arthropod bites and stings. J Am Acad Dermatol. 2004 Aug. 51(2):289. [Medline].

 
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