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Crawford County Home & Garden
Outdoor Pests
Arboviral Encephalitis - What you need to know to protect yourself
Eastern Equine Encephalitis •
St. Louis Encephalitis
• West Nile Virus •
Mosquito Control •
Removing Breeding Sites •
Personal Protection
• Additional
Information
The term “arbovirus” is derived from the phrase “arthropod-borne”. Mosquitoes
and ticks are examples of arthropods. When they feed on a bird or mammal, they
may pick up a virus along with the blood meal. These viruses are transmitted to
humans through the bite of an infected mosquito or tick. The birds and small
mammals usually do not get sick, rather, they maintain and ‘store’ the virus.
Although these viruses are maintained in bird and small mammal populations all
year round, human disease tends to be seasonal, occurring during times of
mosquito activity. Infected mammals or birds cannot directly transfer arboviral
disease to people; it can only be transmitted when an infected mosquito takes a
blood meal. Not all mosquitoes have a virus in them, but certainly, the more
mosquito bites you get, the greater your risk of catching a disease. Symptoms of
human arboviral infections typically begin within 14 days following the insect
bite and consist of fever, headache, rash, muscle and joint aches, listlessness,
possibly encephalitis (swelling of the brain, the most dangerous symptom) and,
sometimes death. The good thing is that most people that get bitten by an
infected mosquito do not get sick. There is no specific treatment for
arboviral infections. Avoiding mosquitoes is the best prevention. There are at
least two different arboviruses that occur in Arkansas. They are St. Louis
Encephalitis (SLE) and Eastern Equine Encephalitis (EEE). Another virus is West
Nile virus (WNV), which first occurred in New York in 1999 was recently found in
dead blue jays in Arkansas.
Eastern Equine Encephalitis
Humans, horses, pheasants, and emus are all very susceptible to EEE. Only a
few human cases of EEE have ever been reported in Arkansas. Infected children
are the most likely to have severe illness or die. EEE is considered the most
severe arboviral encephalitis; the fatality rate can approach 70% in susceptible
people. Those individuals who do recover frequently have permanent, disabling
side effects. In recent years, Arkansans have seen sporadic outbreaks in horses
and emus. Horses that are infected with EEE will show symptoms such as walking
in circles, unbalanced, head drooping and convulsion. Emus that are infected
with EEE will have bloody diarrhea. There is no vaccine for routine use in
humans but one is available for horses and emus and can prevent EEE if
vaccinated regularly.
St. Louis Encephalitis
SLE does not cause disease in animals; it is strictly a human disease. Large
outbreaks of SLE have sporadically occurred throughout the U.S. The symptoms are
typically milder, with most people experiencing flu like symptoms. Those that
are primarily affected are the elderly. Arkansas experiences sporadic cases of
SLE, most going unreported. The largest outbreak in recent years was in 1991
when it hit Pine Bluff resulting in 28 hospitalized with five deaths all over
the age of 60.
West Nile Virus
WNV was first recognized in the Western Hemisphere in the summer of 1999,
when an outbreak occurred in the New York City (NYC) area, infecting 62 people
and causing seven deaths. Many different bird species (especially American
crows) and mammals, including 25 horses in NY, also became infected. Many of the
infected animals died. In 2000, the virus spread geographically; 12 states and
the District of Columbia reported positive findings. In September 2001, four
blue jays found dead in three Arkansas counties (Union, Saline, and Crawford)
were diagnosed with the virus. Prior to the NYC outbreak, this virus had
primarily been reported in South Africa, Middle East, and southwestern Asia. WNV
is like SLE in that most infected people show no symptoms. Symptoms include:
headache, fever, rash, stiff neck, muscle and joint pain nausea, vomiting,
diarrhea and neurological disease or encephalitis. Elderly individuals (> 50
years of age) may be at greater risk of developing severe illness and
encephalitis. No vaccine is currently available for humans, but one has recently
become available for horses. Symptoms in horses are similar to symptoms found in
horses infected with EEE.
In an attempt to protect the public’s health, the Arkansas Department of
Health (ADH) will be testing dead birds, horses, and mosquitoes for arboviruses.
ADH is requesting the public’s assistance in reporting dead birds to their Local
Health Unit, so that delivery and testing of these birds can be arranged. The
Lab will be testing for are West Nile virus (WNV), Eastern Equine encephalitis
(EEE), and St. Louis encephalitis (SLE) virus. The Lab will also be testing
mosquito populations for these viruses. Veterinarians are encouraged to send
serum samples of suspect cases of encephalitis to the Arkansas Livestock and
Poultry Commission Laboratory for free testing of WNV.
Mosquito Control
Mosquitoes breed in any body of water, from small containers such as tin cans
to large bodies of water like lakes or marshes. All these breeding places create
a variety of mosquito problems. Controlling mosquitoes after they have become
adults requires the spraying of insecticides repeatedly over large areas. The
best way to prevent mosquito problems before they get started is to perform
larval control. They may include: eliminating breeding sites, or using
biological controls such as bacteria that kill the mosquito larvae or
introducing predators such as fish.
Removing Breeding Sites
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Dispose of tin cans, plastic containers, ceramic pots or similar
water-holding containers.
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Remove all discarded tires on your property. Used tires have become the
most common mosquito-breeding site in the country.
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Drill holes in the bottoms of recycling containers that are kept
outdoors.
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Make sure roof gutters drain properly, and clean clogged gutters in the
spring and fall.
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Turn over plastic wading pools and wheelbarrows when not in use.
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Change the water in birdbaths.
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Clean vegetation and debris from the edges of ponds.
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Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
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Drain water from pool covers.
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Use landscaping to eliminate stagnant water that collects on your
property.
Personal Protection
- Make sure all windows and doors have screens, which are in good repair
- Stay indoors when mosquitoes are more active
- Wear protective clothing outdoors when mosquitoes are more active
- Use mosquito repellent, (containing 20 to 30% DEET) when it is necessary
to be outdoors
Need More Information?
Contact your Local Health Department or the Division of
Epidemiology at the
Arkansas Department of Health (501) 661- 2184 or 800- 554-5738, Ext.
2184
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