- Historically, arthropodborne
diseases have caused more casualties than combat
injuries. Arthropodborne diseases alone were
responsible for the loss of 15,576,000 man-days among
US Armed Forces during World War II.
- Today, harmful arthropods
represent one of the greatest environmental hazard
to soldiers in the field. The chain of infection for
arthropodborne diseases involves a pathogenic
organism in an infected person or animal (the
reservoir), an arthropod to transmit the disease
(vector), and a susceptible person (the host).
- The significance of vector efficiency in disease
transmission from reservoir to host is related to
many factors. Some of the factors are
species-related such as vector reproductive
capacity, physiology, morphology, and genetics.
- Other factors that affect the vector�s ability
to transmit disease are physical and related to
environmental conditions, such as temperature,
moisture, rainfall, pH, weather, geographical and
topographical location, photoperiod, and wind.
- Soldiers in a field environment must break the
chain of infection for arthropodborne disease or
arthropod injury by limiting arthropod pest
- Arthropods (insects, ticks, mites,
spiders, scorpions, and the like) make up over 75
percent of all animal species. Less than 1 percent of
the 750,000 species of arthropods are potentially
dangerous to humans. However, their impact is
significant due to their high numbers and the negative
results of their activities. The impact is direct
injury and disease transmission to man and other
animals; damage to crops; infestation of stored
products; and destruction of wooden structures. Still,
many species are beneficial as pollinators, predators
of other pests, scavengers of waste, manufacturers of
food, and a part of the natural balance of nature.
However, the economic damage and medical disorders
caused by a few arthropods make some pest management
practices necessary to control the problem pests.
Protection of the soldier from arthropods and
arthropodborne diseases is essential to mission
Affects on Human Health
In addition to disease
transmission, arthropods can cause direct injuries to
man. Bites, stings, and allergic reactions are three
major categories of injuries caused by arthropods.
Arthropods also affect man by annoying and disturbing
him. The sound of a single mosquito buzzing around your
head while your are trying to sleep is annoying.
Standing guard with gnats buzzing around your face can
be disturbing. Also, finding cockroaches or other
insects or parts of insects in your food is disturbing.
The problems of arthropod injury and the exaggerated
fear of arthropods can even result in psychiatric
- Biting Arthropods. Arthropods bite
to feed, probe (taste), or defend themselves. Most
penetrations of human skin are made by mouthparts that
are developed for ingesting blood, tissue, and tissue
fluids of animals or plants. These bites usually
result in the arthropod injecting salivary fluids or
regurgitating its digestive tract products into the
man or animal. Some biting arthropods can also produce
skin injuries. Each individuals reaction to arthropod
bites can be very different. Biting arthropods are
grouped according to the duration of host contact as
(short-term) or prolonged (long-term).
- Short-term host contact.
Most arthropods that bite man have only short-term
host contact. Bloodsucking arthropods are frequently
winged or highly mobile. This accounts for their
ability to quickly attack and escape capture or
detection. Some arthropods hide in structures close
to the host and only feed when the host is nearby.
Others that bite may not have intended to attack,
but did so in defense or by mistake. Arthropods can
bite in several stages of their development; that
is, adult, larvae, or nymph stages. The mouthparts
are generally classified into chewing or sucking
types. Chewing mouthparts are generally not used for
skin penetration. Usually, injuries of this type are
not reported, but secondary infections may occur due
to bacterial contamination. Sucking mouthparts are
structured for skin penetration.
- Bloodsucking (hematophagous)
normally from warmblooded animals (including man),
is used both for life support and growth and/or
egg development. The mouthparts of sucking
arthropods vary greatly in structure from
arthropod-to-arthropod. For example, adults of the
order Diptera (two-winged insects) have the most
diverse mouthparts. Only the females of the
mosquitoes, black flies, biting midges,
horseflies, and deer flies are bloodsuckers, while
both males and females of tsetse flies and stable
flies are bloodsuckers. The mouthparts are
different within each of these families of Diptera,
but the goal of a blood meal is the same. Other
examples of arthropods that are short-term are
fleas, true bugs (conenose bugs and bedbugs), and
- Nonbloodsucking (nonhematophagous)
arthropods. Some plant-feeding arthropods and
some arthropod predators have piercing/sucking
mouthparts, which are capable of penetrating the
human skin. Bites from these arthropods can be as
painful as bloodsuckers, if not more so. Bites
from these arthropods are usually an act of
- Long-term host contact.
Some biting arthropods require a considerable time
on the host to complete a normal life cycle. Since a
continuous food supply is available on one host, the
search for another host is reduced. Most of these
arthropods are categorized as parasites. They are
classified as either ectoparasites or endoparasites.
Ectoparasites (those living outside the host body)
may be flat (fleas) or thin (lice) which allows them
to travel easily through a hairy environment. Their
feet are specialized for holding on to hair. The
mouthparts of ticks and mites are designed to anchor
their bodies to the host. Endoparasites (those
living inside the host body) are usually soft-bodied
(fly larvae, mites) without legs or with very short
legs; their bodies usually have specially arranged
spines or hairs.
- Stinging Arthropods.
Some arthropods affect man by injecting venom (insect
toxins) through stingers, fangs, modified front legs,
or spines. An arthropod�s injection of poison is in
defense or to kill prey. Usually, man is envenomized
by arthropods in defense of themselves and their nest
- Venoms from bites.
Spiders and centipedes are arthropods in the
category that uses mouthparts for envenomization.
Most spiders use venom to kill prey. Man is not part
of a spider�s diet. The fangs of many spiders cannot
penetrate the human skin. Some species have venom
that is more poisonous than other venomous animals,
including snakes. Fortunately, most spiders are not
aggressive, but will defend themselves and their
eggs and/or webs. Antivenom has been developed for
the venom of some species of spiders, but they may
not be immediately available for use. Some of the
more toxic spiders are night hunters, and by day,
they hide in clothing and boots that were left on
the floor or in tents on the ground. Less common are
the bites of centipedes that are also night hunters.
In the tropics, some species of centipedes reach 25
centimeters in length; a bite by such a large
specimen could be serious.
- Venoms from stings. The number of soldiers
seeking medical assistance because of arthropod
bites is far fewer than those seeking aid because of
bee, wasp, hornet, or ant stings. Stings from these
arthropods are frequently the result of defensive
action. A single sting to an allergic person can be
fatal. Even to a person who is not strongly
allergic, medical complications due to swelling can
occur with stings to the face, neck, or throat.
Stings usually occur during daylight hours. However,
night maneuvers can result in individuals running
into paper wasp nests and being stung by wasps
trying to protect their nests; or an individual may
stand on an anthill and receive numerous stings from
the ants trying to protect their nest. Therefore,
individuals who are highly sensitive or have severe
reactions to stings should carry an emergency first
aid kit for stings as prescribed by a physician.
Obviously, high-risk persons should use extreme
caution in tropical areas. Another venomous
arthropod with a potent sting is the scorpion.
Scorpions are active at night. During the day
scorpions are usually well-hidden from the light;
they hide under rocks or in piles of debris outside
and in clothing, cabinets, boxes, and footwear
indoors. Stings often are the result of individuals
walking barefoot or in stocking feet, or because
they use their hand to move the object where the
scorpion is hiding. Also, stings occur when
individuals put on clothing or footgear without
first shaking the item to make sure that it is free
of unwanted arthropods. Some scorpion venoms are
very painful or they may be deadly, while others are
not. The absence of initial pain is not always an
indication of no problem. The lack of or the
nonavailability of antivenom and the possible
medical problems associated with the use of
antivenoms, even if they were on hand, are
additional reasons for avoiding scorpion stings.
- Allergy. Allergic reactions are
caused by both the bites and stings of arthropods.
Additionally, arthropod parts (live or dead) and their
body fluids can cause allergic reactions. Allergic
reactions are extremely variable in different people
ranging from very mild to severe reactions. Highly
sensitive persons should be prepared to deal with
their problems in case they are bitten, stung, or
exposed to other arthropod allergens.
Diseases transmitted to
man by arthropods are some of the most serious known to
man. Uncontrolled, these illnesses can cripple or
destroy military forces. The effect of these diseases on
man can range from a very mild illness to death. For
examples of arthropodborne diseases and their vectors
see Table 2-1. House flies and other flying insects that
are attracted to human wastes or other organic material
can spread disease organisms to food and water. The
disease organisms or parasites of humans are carried
from diseased humans or animals (reservoirs) by
arthropods (vectors) to other humans or animals (hosts).
By employing individual PMM, soldiers can stop
arthropodborne diseases from being a factor in their
lives and in their units mission accomplishment. The
most common arthropodborne diseases that affect combat
troops are discussed below.
KISSING BUG (REDUVIID)
SAND FLY (PHLEBOTOMINE)
OR PHLEBOTOMUS FEVER
SAND FLY (PHLEBOTOMINE)
(PARTICULARLY THE HOUSE FLY)
COCKROACHES (BY FOOD CONTAMINATION)
- Malaria. Malaria is a serious disease
occurring most commonly in tropical and semitropical
regions. It is caused by a microscopic parasite
carried by the Anopheles mosquito. This parasite
destroys blood cells and causes chills, fever,
weakness, and anemia. If untreated, malaria can cause
- Yellow Fever. Yellow fever is a viral
disease transmitted by the Aedes mosquito. It occurs
in tropical Africa, Central America, and tropical
South America. Symptoms are fever, headache, backache,
jaundice, and internal bleeding. If untreated, yellow
fever can result in death.
- Dengue Fever. Dengue viruses of multiple
types are now endemic throughout most tropical areas
of the world and are highly endemic in Southeast Asia,
the Philippines, West Africa, and northern Australia.
Like yellow fever, it is transmitted by the Aedes
mosquito. Symptoms are fever (lasting about 5 days),
intense headaches, skin rash, and muscle pain which
can be severe; for this reason, another name for
dengue fever is �breakbone� fever. The disease seldom
results in death, but the recovery time is usually
long and the victim may be fatigued and depressed.