As "alarming" news of an increasing number of cases of West
Nile Virus (WNV) in wild birds, horses, pets, and humans are reported across
the country; nearly everyone is concerned about keeping their "entire family" safe.
The potential magnitude of this national problem given an estimated population
of 310 million people in addition to another 52 million dogs and 48 million
cats is staggering. While the actual threat of WNV reaching epidemic proportions
seems remote, the remedy for this problem - the use of toxic insect repellants
- maybe introducing an even greater hazard. In addressing this issue -
namely the use of insect repellants with potentially harmful ingredients
- answers to the following questions are vital.
N' Out Natural Insect Repellent for Pets
1. What is West Nile Virus?
West Nile virus (WNV) is an "arbovirus" that causes encephalitis (inflammation
to the brain). Blood-feeding insects such as mosquitoes transmit these viruses.
Mosquitoes draw the virus from infected birds and transmit it to animals and
humans through bites. West Nile viral encephalitis develops in animals and
humans when the virus multiplies and crosses the blood brain barrier. Most
infections with WNV have been identified in wild birds, but the virus can also
infect horses, dogs, cats, domestic rabbits, domestic birds and humans. The
WNV, which originated in Uganda, was discovered in North America in 1999. Since
that time the West Nile Viral Encephalitis has spread to 37 states and the
Distinct of Columbia.
2. What is the Risk of Contracting West Nile Virus?
The risk of becoming ill with WNV from a single mosquito bite is extremely
low. Transmission of WNV is almost exclusively by mosquitoes that pick up the
virus from infected birds, and then bite another animal or person. In all the
intensive research and surveys that have been done, there are no reports of
transmission from person to person, or from animals directly to humans, or
For humans, the risk associated with WNV is highest in those over 50 years
of age. It is unknown if immunocompromised persons are at increased risk for
WNV disease. In areas where mosquitoes carry the virus, fewer than 1% of the
people bitten, and subsequently, infected become severely ill. As of August
9, 2002 this year out of 135 reported cases nationwide only seven deaths have
Dogs or cats become infected the same way humans become infected - by the bite
of infectious mosquitoes. The virus is located in the mosquito's salivary glands.
During blood feeding, the virus is injected into the animal. The virus then
multiplies and may cause illness. Mosquitoes become infected when they feed
on infected birds, which may circulate the virus in their blood for a few days.
It is possible that eating dead infected animals such as birds could infect
dogs and cats, but this is unproven.
WNV affects horses more often than other domestic animals. Many horses infected
with WNV do not develop any illness, but of the 85 that did become ill in the
1999 or 2000 outbreak, 32 (38 percent) died or were euthanized. As of July
25, there were 47 confirmed cases of WNV in horses in 2002. Of the 47, seventeen
either died or were euthanized.
Other animals including wild birds infected with WNV in the United States are
most often found dead; therefore descriptions of clinical signs in wild birds
are not readily available. Clinical signs associated with West Nile virus infection
in dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, and domestic
birds are not well described. It appears, however, that, although they may
be infected, many of these latter species may not develop clinical signs of
3. Identifying and Treating West Nile Virus?
The WNV infections in humans are relatively mild with flu like symptoms including
fever, headache, body aches, and sometimes swollen glands or rash. Severe signs
include high fever, neck stiffness, muscle weakness, and convulsions. Although
no cases have been reported among dogs and cats, the disease can occur. If
so, one could assume at least some symptoms are similar to those in people.
West Nile Virus has been reported only in the eastern half of the U.S. and
is expected to spread to the northwest. Fortunately, with this type of virus,
birds, horses, humans and other animals quickly develop immunity and the infection
rate is expected to peak and then decrease to a persistent, but low level.
Horses are definitely susceptible. For horses the most common sign is weakness.
Weakness may be indicated by a widened stance, stumbling, leaning to one side
and toe dragging. In extreme cases paralysis may follow. Approximately 40%
of cases of WNV encephalitis in horses proved fatal during the 1999 outbreak
in the U.S. Other livestock and poultry do not commonly show wellness if infected
with WNV. Diagnosis of WNV encephalitis is based on a history of exposure,
clinical signs and results of diagnostic blood tests. As for all viral diseases,
treatment consists of providing support while the affected individual's immune
system responds to the infection.
4. Preventing West Nile Virus?
Given that mosquitoes are associated with WNV transmission, the key to preventing
or controlling future outbreaks of WNV among horses and other animals is to
control mosquito populations and to prevent horses from being exposed to any
adult mosquitoes that may be present. Because pets could be infected the same
way people are, the key to prevention is to prevent mosquito bites. Products
to prevent fleas and ticks have no effect on mosquitoes. There are over the
counter products, however, available to repel mosquitoes. Similar recommendations
would apply for other pets, livestock, or poultry should illness due to WNV
in those types of animals come to be commonly recognized. Generally accepted
- Reduction of Mosquito Breeding Habitat
by reducing sources of standing or stagnant water to minimize breeding
- Decrease Human and Pet Exposure to
Adult Mosquitoes including:
- Maintaining the integrity of screened
housing to provide mosquito free areas.Use insect repellent in conjunction
with other measures and use of safe ingredients. While the use of DEET
is highly recommended for use in repelling mosquitoes, both the CDC
and EPA have issued extensive cautions about its use.*
- Limit outdoor exposure particularly
at dawn and dusk time of day when mosquitoes are generally most active.
- Cover up with protective clothing
in conjunction with other protective measures.
- Vaccination is now available as an
option for horses:
- In 2001 a license was issued by the
USDA-APHIS Center for Veterinary Biologics for an equine WNV vaccine.
* For more information contact the National Pesticide Information Center
(NPIC) at 1.800.858.7378 or 1.800.222.1222 for information on nearest the
Poison Control Center to you.] Repellents should be used according to their
label instructions regarding appropriate species, method of application
and other precautions. Some repellents contain permethrin as their active
ingredient. Topical application of a product containing a synthetic permethrin
compound as the active ingredient may offer the best combination of safety
and efficacy. While these sprays do prevent some mosquitoes from biting,
others will penetrate. Warning: Permethrin sprays are deadly if used on
There are a few all natural products using citronella which are effective
and safe in repelling mosquitoes and do not have the same side effects
that deet can have. For information on an all natural, deet free repellent
for people see Bug N' Out. For an all natural, deet free repellent for
dogs and cats see Bug N' Out for Pets.
Published Summer 2001