Eastern, Lacrosse, St. Louis & Western encaphalitis

Encephalitis is an inflammation of the brain, which can be caused by viruses transmitted through the bite of an infected mosquito. Susceptibility to clinical disease is highest in infancy and old age. With an incubation period between 5 and 15 days, mild cases result in a febrile headache while severe cases present with acute onset of high fever and headache, but most infections are asymptomatic. Case fatality rates range from 0.3% to 60% with Eastern Equine exhibiting the highest.

Each disease is caused by a specific virus, occurs in specific geographic regions, transmitted by specific species of mosquitoes and may follow certain cyclic patterns based on multiple environmental factors.

Risk Reduction

Effective risk reduction for mosquito-borne diseases within the NPS requires all employees and visitors to be knowledgeable and proactive in taking necessary steps to minimize exposure. Primary risk reduction practices include eliminating man-made mosquito-breeding habitat, avoiding activities when mosquitoes are most active, and wearing long sleeved shirts and pants. Many species of mosquito breed in stagnant water, therefore, it is critical that containers such as tires, buckets, birdbaths, gutters and miscellaneous debris are either removed or not holding water. The use of an insect repellant containing DEET, picaridin or oil of lemon eucalyptus (p-menthane or PMD) are effective against mosquitoes and should be used during periods of high mosquito activity. DEET should be used with caution on children – DEET is not recommended for the very young. Products containing oil of lemon eucalyptus should not be used on the very young.

References

Health Information, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Department of Health and Human Services.