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Bed Bugs
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This module is intended to serve as a source of basic
information needed to implement an integrated pest management program for fleas.
Any pest management plan or activity must be formulated within the framework of
the management zones where it will be implemented. Full consideration must be
given to threatened and endangered species, natural and cultural resources,
human health and safety, and the legal mandates of the individual parks.
Recommendations in this module must be evaluated and applied in relation to
these broader considerations.
Although there are over 250 species of fleas described in North America (Pratt
1957), only a few are commonly encountered by humans with enough frequency to be
considered pests (Ehman and Story 1982). These include the cat flea, Ctenocephalides
felis (Bouche), the dog flea, C. canis (Curtis), the human flea, Pulex
irritans (L), and the oriental rat flea, Xenopsylla cheopis
(Rothschild). Other species, such as the rabbit flea, Cediopsylla symplex,
the mouse flea, Ctenopsyllus segnis, the ground squirrel flea Diamanus
montanus (Baker), and Oropsylla hirsuta, a flea that feeds on prairie
dogs, may achieve pest status when their host mammals nest in or near structures
or the fleas attack hunters and hikers. Some, such as the northern rat flea,
ground squirrel flea, and Oropsylla hirsuta are important vectors of
sylvatic plague, bubonic plague, and murine typhus.
Flea management is best done via management of the host animal's habitat. Since
fleas must spend part of their life cycle on their host, the chances of
encountering fleas in areas of the host's habitat where it spends most of its
time (e.g., its den or nest) are much greater than in a general area, such as a
field or barn in which the host may or may not be found at a given time. One
author has suggested that most fleas spend more time in the host nest or burrow
than on the host itself (Benton 1980). This is the emphasis that will be placed
on flea management strategies in this module.
 Flea
Larvae
IDENTIFICATION AND BIOLOGY OF FLEAS
This document will deal with the four most commonly encountered flea species
mentioned above: the cat flea, the dog flea, the human flea, and the oriental
rat flea. These fleas are found throughout the United States and are most likely
to be encountered in mammal and bird nests or in pet bedding. Adult fleas are
ectoparasites of their hosts, but unlike many other ectoparasites they do not
spend the majority of their life cycle on their host.
Females deposit eggs in groups of 1 to 18 on the host after a blood meal. Some
species, such as the cat flea, can deposit up to 25 eggs per day and over 1000
in a lifetime. Eggs soon drop off or are brushed off. Due to their spherical or
oval shape, they roll into cracks and crevices on the floor or in or near nests
and bedding. Eggs are whitish and 1/32" in diameter. Eggs hatch in 2 to 21
days.
Larvae are approximately 1/4" when first hatched, white, and have fine
hairs. They lack legs or eyes but possess biting mouthparts. Most species feed
on dried blood from the host (in the form of adult flea feces) or organic debris
present in cracks and crevices. They also feed on cast larval skins. Depending
on the availability of food, relative humidity, and other environmental factors,
larvae pass through three stages (instars) in one week to several months.
Optimal temperatures for larval development are 65
to 80
F. Larvae need a relative humidity of at least 50%. It is important to realize
that even if the relative humidity of the ambient air is not this high, it could
be much higher in the microhabitat of a burrow or den. Larvae can also survive
short exposures to below freezing temperatures (Silverman and Rust 1983). Larvae
pupate within cocoons spun from silk and may be covered with debris.
The pupal stage usually lasts approximately one week. The newly emerged adult
may remain in the cocoon for some time; under adverse conditions, the adult may
spend up to a year in the cocoon. Emergence occurs in response to pressure
applied to the cocoon or detection of host warmth, vibrations, or carbon dioxide
in the host's breath.
Adult fleas are small, brownish insects flattened from side to side, without
wings but with powerful jumping legs. Adults can live for several years and go
without feeding for months at a time under extreme conditions. Fleas can remain
in a structure long after the host mammals have been removed. Depending on the
species and environmental conditions, adults can breed from two weeks to two
years after emerging. Adults feed on blood, and females deposit eggs only after
a blood meal. Most species remain on the host only long enough to feed. Nearly
all species have host preferences but are not restricted to any one host
species. This trait is responsible for the transmission of several diseases
(e.g. plague or murine typhus) from one host species to another. Adults prefer
warm humid places and will leave a host if it dies.
Outdoors, fleas are most abundant during humid, rainy summers and are more
common outside in the southern United States than in the north. Indoors, warmth
and high relative humidities are conducive to large populations. The sudden
appearance of large numbers of adult fleas in mid-summer and fall ("flea
seasons") is due in large part to the onset of higher humidities and
temperatures which permit larval development to accelerate. Larvae may undergo
arrested development in less than favorable conditions.
Medical Importance of Fleas
Flea bites vary in effect from short-lived itching welts to an overall rash to
symptoms which may last over a year, depending on the sensitivity of the victim.
Young children are more sensitive than older persons. Commonly, a small red spot
appears where the skin has been pierced. Little swelling ensues, but the spot is
accompanied by a red halo of irritated skin which usually lasts for several
hours to a day.
Fleas are vectors of several diseases important to human health including
plague, murine typhus, and tularemia. The oriental rat flea is the most
important plague vector from rodents (primarily rats) to humans, but at least 30
other flea species can also transmit the disease, including the northern rat
flea, dog flea, cat flea, and the human flea. Plague (in the sylvatic form) is
endemic in the western United States among small rodents such as chipmunks,
ground squirrels, and prairie dogs.
Nearly all known cases of plague in humans in the United States since 1925 have
been associated with wild rodents (mostly from the Rocky Mountain states) and
their fleas. The greatest threat to humans exist when domestic rats are exposed
to infection from wild rodents in areas adjacent to human communities.
Murine typhus is a mild form of epidemic typhus that is usually spread by the
human louse. The Norway rat population is the main reservoir of the disease. The
disease is most common in the southwestern and Gulf states. The disease is
commonly spread from rat to rat, and from rat to human by the oriental and
northern rat fleas. It has also been transmitted by cat fleas from infected
feral cats.
Fleas are also vectors of tularemia, a disease related to plague. The natural
reservoirs of tularemia are cottontail rabbits in the East, and jack rabbits in
the West. Most cases reported are by hunters.
Fleas can also be intermediate hosts of several species of tapeworm including
species which parasitize humans, dogs, and cats.
MONITORING AND THRESHOLDS FOR FLEAS
Fleas can be monitored in several ways. The simplest is to count and collect
fleas landing or crawling on an observer's lower legs for one minute. In making
surveys, trousers should be tucked into white socks to prevent bites and make
collecting easier (socks can be put on over shoes). Light-colored trousers are
preferred to provide greater contrast and facilitate counting and collection. A
variation on the above is to wrap fly paper (sticky side out) around the lower
legs and count fleas adhering after a predetermined interval (Cole and Burden
1978).
Fleas may also be combed off animals for an index of animal infestation. Do this
over a white surface so fleas can be easily observed (Ehmann and Storey 1982).
Pet bedding should be periodically checked for flea eggs and dried-blood feces (frass)
of adult fleas. This has been described as "salt and pepper" because
it looks like small flecks of black and white debris. The frass is generally
cylindrical, twisted, and about 1/16" long. It is dark in color. Larvae and
pupae can be found at the edge of pet bedding or animal nests.
Indoors, five or more fleas on the legs of observers in less than one minute is
indicative of severe infestation.
NON-CHEMICAL CONTROL OF FLEAS
Several studies have indicated that fleas spend the majority of their life
either on the host or in the host's bedding or nest, so flea management should
focus on these. In outdoor settings, the emphasis should be on spot treatment of
nests with an insecticide. Exclusion of the host animal from an area may be
desirable as well, but the feasibility of this strategy will vary with the
animal and the location of its nest. In the case of domestic animals, sanitation
should be the focus of a flea management program. Regular cleaning of bedding
and other areas where the animal spends the majority of its time should reduce
flea populations to non-irritating levels.
In areas where plague is endemic (e.g. the southwestern United States), efforts
should be made to keep humans and fleas (and their wildlife hosts) separate.
Prairie dog towns should not be allowed to expand into campgrounds and other
developed areas. Camping and other outdoor activities should be restricted
during an outbreak when fleas seek other hosts. Prairie dog burrows can be
dusted with insecticide. Check with Public Health Service officials if your area
is affected.
In most other cases, fleas are considered pests due to the nuisance caused by
their bites. In these situations, management decisions should be made on a
case-by- case basis.
Sanitation
Fleas require warm-blooded hosts for development and for egg maturation.
Elimination of suitable habitat for wild rodents and other animals near
structures will often reduce flea population levels. Screened vents prevent
animals from resting inside or underneath structures. Eliminating vegetation
close to structures and raising woodpiles off the ground reduces rodent
harborage.
Indoors, wash or vacuum all pet bedding and sleeping areas on a regular basis.
Cracks and crevices should be vacuumed and sealed, especially the area between
the baseboard and floor. Dispose of vacuum cleaner bags to prevent reinfestation.
Pets should be washed regularly and treated with insecticides if necessary.
Ultrasound
The ultrasonic collar is sometimes for the control of fleas on domestic animals.
A recent study (Hinkel, Koehler, and Patterson, 1990) showed that ultrasound
devices are ineffective.
Insect Growth Regulators
A new technology in the management of fleas is the use of insect growth
regulators (IGRs). These substances are similar to chemicals produced by the
flea to regulate the shedding of its skin during molting. They work by
interfering with the molting process, thus preventing the immature flea from
developing into an adult. This method of control is a long-term process, since
it will only kill larvae as they molt. A recent study using pyriproxyfen (sold
as Nylar
), an insect growth regulator reported to be effective against several
insects, examined its effectiveness against the cat flea. One problem with
insect growth regulators is that they break down when exposed to light, limiting
their outdoor use. In this study, Nylar
was determined to be stable when exposed to light. It was found to
persist in home yards for three weeks after application and to prevent
development of 90% of the fleas in treated areas (Palma and Meola 1990). Another
effective IGR for flea management indoors is methoprene (trade name Precor
). It is important to combine the use of a material such as this with
observations of the infested animal's movement so that only areas where it
spends the majority of its time are treated.
Flea Predators
Fleas are preyed upon by ants and beetles that feed on larvae in the host's nest
(Fox and Bayona 1968).
CHEMICAL CONTROL OF FLEAS
Insecticides are also part of a flea management program. These are applied to
areas where fleas are most likely to breed, including animal bedding, cracks in
floors, and baseboards. Many veterinarians also recommend the use of indoor
foggers to apply pesticides to rooms where domestic animals spend the bulk of
their time. Flea collars are not considered to be effective (Whiteley 1987).
When insecticides are used, it should be in conjunction with sanitation (Arthur
et al. 1989). One difficulty with the use of insecticides as part of a flea
management program is the ability of the adult flea to remain in its cocoon as a
preemerged adult. This means that the adult flea can remain in the cocoon in
which it pupates until it encounters a suitable host. Insecticides have been
found to be ineffective against these preemerged adults (Rust and Reierson
1989). This highlights the importance of sanitation as the key element in a flea
management program.
With eight legs instead of six, the tick is cousin to the
spider, not the insect. It's claim to fame is its penchant for spreading disease
as it feasts on mammal blood. There are several species that feed on dogs,
including the wood tick, the brown dog tick, and the deer tick, and they all
thrive in tall grass, shrubby areas, and woods.
Ticks can carry Rocky Mountain Spotted Fever, encephalitis,
tularemia, tick paralysis, and Lyme disease, so it is important to prevent tick
infestations in domestic dogs.
Lyme disease, a frightening collection of symptoms that can
mimic fatigue, heart problems, and arthritis and cause birth defects, affects
dogs and horses as well as people and has been found in every state but Montana
and New Mexico. Lyme Disease is tough to diagnose but can be treated with
antibiotics.
Unlike the flea, the tick is a sluggish mover and can easily
be picked off the dog with tweezers as it crawls about looking for a feeding
spot. So, after a walk in the woods, check Bowser (and yourself) for ticks from
stem to stern. Look for feeding ticks around the dog's head and ears and in his
armpits and the inside of his thighs. If you miss one as it crawls, you'll
likely find it when it latches on to feed as the engorged body is hard to miss
in a hands-on inspection.
Daily grooming can find ticks that have not yet become
embedded in the skin. Ticks can be picked up on the comb and flicked into a
container of alcohol.
Embedded ticks should be removed immediately. First, forget
all you ever heard about coating ticks with petroleum jelly, burning their rear
ends with a match or lighted cigarette, dousing them with lighter fluid or
gasoline, etc. Just protect fingers from the tick's body fluids with surgical
gloves or a plastic bag, grasp the tick firmly, rock it back and forth a few
times, and pull it out. If a patch of skin comes along, it's unlikely that any
of the tick's head has been left behind.
A dab of antiseptic cream on the spot where the tick was
removed will help prevent local infection, especially on tender ears, a favorite
feeding place for ticks.
To control ticks in the environment, keep grass trimmed and
control the spread of shrubbery and tall weeds. Perimeter pest control
both indoors and out can also reduce tick infestation.
The mosquito prefers to bite people but will settle for Fido.
Although the itchiness of mosquito bites is short-lived, this insect carries the
heartworm microfilariae, the immature stage of the
heartworm, and can transfer it to the dog. Heartworm infestations kill dogs.
Since heartworm preventive can have adverse effects on dogs already infested
with the parasite, owners should have their dogs tested each spring. Once the
dog is found to be heartworm free, the preventive can be given.
Mosquitoes are likely to be abundant in many areas this summer
after an unusually rainy spring. After ingesting enough blood to satisfy their
reproductive needs, the female mosquito lays her eggs in water, where they
develop into larvae and adults. Elimination of standing water helps control
mosquitoes, so remove any debris that can catch rain water and dump the water
from plant-pot saucers. If you have a pond, keep the water aerated to disturb
the surface tension.
If you walk with your dog, avoid marshy places.
If you live in mosquito country be sure to get Bowser checked
for heartworm. This is a parasite infestation in which prevention is cheaper and
safer than cure and where early diagnosis is a life-saver.
Unfortunately, there is no specific control measure for
mosquito control outdoors. Mosquitoes may travel from hundreds of feet
away and be nested around a local stream. The most simple means of
mosquito control is via the use of repellants. Be sure to follow all
instructions and make note of precautionary statements labeled on these
repellants.
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