Transcript 13. Medical arachnoentomology

Medical arachnoentomology.
Arthropods as pathogenic organisms
and carriers of agents of infections and
invasions
Lecturer: ass. Nedoshytko Khrystyna
Plan of lecture
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Phylum Arthropoda: general characteristic,
classification, medical importance.
Crustaceans as intermediate hosts of helminthes.
Class Arachnida: general characteristic,
classification, medical importance.
General characteristics, classification of class
Insecta.
Order Anoplura (lice). Morphology, medical
importance, methods of control.
Order Siphonaptera (fleas). Morphology, medical
importance, methods of control.
General characteristics, classification, medical
importance of order Diptera.
Anopheles, Aedes, and Culex mosquitoes and
their role in transmission of infections.
• Three-fourth of all animal species belong
to the Phylum Arthropoda. The name
“arthropod” comes from two Greek words,
arthros, jointed, and podes, feet.
All members of the Phylum Arthropoda
share the following characteristics:
• 1. Arthropods have jointed appendages.
• 2. The arthropod body is segmented.
• 3. Arthropods have an exoskeleton.
• 4. Arthropods have a ventral nervous
system, an open circulatory system, a
digestive system, and specialized sensory
receptors.
Phylum Arthropoda includes
3 classes of medical
importance:
 1.Class Crustacea: cyclops,
crabs.
 2. Class Arachnida
(Octapoda): scorpions,
spiders, ticks and mites.
 3.Class Insecta (Hexapoda):
mosquitoes, flies, bugs, lice,
fleas.
Class Crustacea
Most crustaceans have two pairs of
antennae, three pairs of chewing
appendages, various numbers of
pairs of legs.
• Crustaceans differ from the insects
in that they have legs on their
abdomen as well as on their thorax.
• Medical importance: 1)Cyclopes
are intermediate hosts of the fish
tapeworm (Diphyllobothrium latum)
and Dracunculus medinensis.
• 2) crabs or crayfish are
Intermediate hosts of the
Human lung fluke
(Paragonimus westermani).
Class Arachnida.
• The Class Arachnida is a group of more than 100,000 species, including
spiders, scorpions, ticks, and mites.
• Most arachnids are adapted to kill prey with poison glands, stingers, or
fangs.
• Arachnids have a body that is divided into a cephalothorax and an abdomen.
• Attached to the cephalothorax are 4 pairs of legs, a pair of chelicerae, and a
pair of appendages called pedipalps.
The pedipalps aid in chewing; in some species pedipalps are specialized to
perform other functions.
Arachnids undergo incomplete metamorphosis.
Class Arachnida includes 3 orders of
medical importance:
Order Scorpiones.
Order Araneae (spiders)
Order Acari (ticks and mites).
Class Arachnida:
Order Scorpiones: Scorpions
E. Tenczar
E. Tenczar
Lined Devil Scorpion,
Vaejovis spinigerus,
female from Arizona with young
Flat Rock Scorpion,
Hadogenes troglodytes,
female, native to
South Africa
Interesting Facts
about Scorpions
• Scorpions live everywhere except the Arctic and Antarctic
• Male and female scorpions find each other by vibration, scent, or
touch. Then they dance together for half an hour or more.
• Females often eat the males when they are done with the dance.
• 25 types can harm/kill man
• Alive before the dinosaurs
• Scorpions have 8 legs and 2 claws.
• The bigger the claws are, the less
• venom it has.
Scorpions differ from spiders in two ways:
- Scorpions have greatly enlarged pedipalps, which they hold
in a forward position.
- They also have a large stinger on the last segment of the
abdomen.
Scorpion Sting Symptoms
A scorpion sting is never fun. The following are common
symptoms of a scorpion sting:
• Intense pain at the sting site
• Mild swelling around sting site
• Numbness in area of sting
• Sensitivity to touch
• Nausea or vomiting
• Excessive salivation
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Stepwise first aid
If a scorpion stings you, follow this scorpion sting first aid
plan for minimization of pain:
• Wash the affected area: If possible, get the site of the sting
under cold water immediately.
• Medicate topically: Apply a layer of ointment containing an
antihistamine, a corticosteroid, and an analgesic.
• Apply ice: Hold a bag of ice over the ointment on the area. The
ice will reduce the pain and inflammation.
• Medicate orally: Take one dose of Benadryl (antihistamine)
and one dose of a pain killer (acetaminophen).
• Go to the hospital: Because some scorpion stings can be
fatal, you will need to go to the emergency room to get
evaluated for scorpion anti-venom. If possible, get someone
else to drive you.
• Ice as needed: Keep applying ice until pain is tolerable. You
may experience pain for any length of time between a few
hours to a couple days.
Spiders are not a “bug”
• Spiders are not insects
they are part of a group
called Arachnid
• There are more than
35,000 different species
of spiders
Arachnophobia
• Arachnophobia is the
fear of spiders
• This is the number
one fear of Americans
today
• Although most spiders
are harmless and
helpful to our lives
This spider has a
venomous bite
that causes
serious wounds
Spider Eyes
• Most spiders have either six
or eight eyes
• Even so they cannot see far
away
• They use the hair on their
bodies as sensors to feel
their way around and to tell
when other animals are
near
How dangerous are black widow
spider bites?
• If a black widow spider bites a person, do not panic!
Very often the black widow will not inject any venom into the
bite and no serious symptoms develop. Wash the wound
well with soap and water to help prevent infection.
If muscle cramps develop, take the patient
to the nearest hospital.
Some victims, especially young children,
may be admitted overnight for observation
and treatment.
There is treatment for a black widow spider
bite that can take care of the symptoms.
Various medications are used to treat the
muscle cramps, spasms and pain of a bite.
Black widow spider antivenin is seldom
necessary.
Order Acari
• Most mites are small, less than 1 mm long,
the adult length from 100 nm to 2 cm.
• the cephalothorax and abdomen are fused into
an unsegmented ovoid body.
• Respiration occurs either by means of tracheae
or directly through the exoskeleton.
• They are found in virtually every terrestrial,
freshwater, and shallow marine habitat known
and feed on fungi, plants, and animals; they act
as predators and as internal and external
parasites of both invertebrates and vertebrates.
Sarcoptidae
“Scabies Mites”
• Sarcoptes scabiei
Also called the “itch mite” of
humans
Not Vectors of any disease.
• Morphology: male (0,2
mm) is smaller than
female (0,4 mm).
• Body is oval, convex
dorsally and flat ventrally.
Sarcoptes scabiei
(itch mite)
Mouthparts:
a) rudimentary hypostome
without teeth.
b) chelicerae end in pincer-like
structures.
c) pedipalps are short and 3segmented.
The whole cycle takes about 2
weeks.
small male
large female
Distribution
• Worldwide
• All races and socioeconomic classes
• All climates
• 300 million cases annually!
Behavior
• Burrowing initially occurs in thinner skin of
the body.
– Bend of knee and elbow.
– Webbing between fingers and folds of the
wrist.
– Genitalia and buttocks.
– Breasts.
Scabies Rash
Life cycle
Transmission
Spread by ovigerous female mites through:
– Personal (prolonged close) contact
– Occasionally by infested sheets (rare).
– Touching or shaking hands (unlikely).
– Sexual activity.
– Among children (outbreaks).
– Mites can survive up to 24 hours off host.
Diagnosis
Diagnosis is made by
- itching of affected surfaces
at night
- specific lesions
- finding of the parasite in the
tunnels by a needle.
Control is provided by
- proper treatment of infected
persons
- sterilization of clothes and
bedding
- personal cleanliness.
Ticks
Ticks are divided into hard-bodied ticks (family Ixodidae)
and soft-bodied ticks (family Argasidae)
Ticks are blood-feeding ectoparasites
(parasites that occur on the surface of their host).
TICK LIFE CYCLE
Life cycle:
- female ticks lay
eggs.
- Larvae hatch, feed
on blood and then
drop to the ground.
- Larvae molt into
nymphs.
- Nymphs feed on
blood and molt into
adults.
- Adult male and
female feed on
blood.
Anatomy of IXODES ticks
Size
Female Deer
Tick
Male Deer Tick
Crawling
All stages of I. ricinus will feed on humans, and their bite can
be painful. This tick can also transmit several diseases that
affect humans, including Crimean–Congo hemorrhagic fever
and Lyme disease.
Female Deer Tick Larvae
Ticks
• Medical importance.
• - Mechanical injury by the bite.
• - Tick paralysis: progressive flaccidity due to a failure of acetylcholine
liberation in the neuromuscular junction. Tick’s toxin produces a block in
the motor nerve fibers. The toxin is elaborated by the tick’s ovaries and is
secreted by salivary glands.
• Vectors of diseases:
• -hard-bodied ticks (Ixodidae) are carriers of rickettsial, spirochaetal, viral,
bacterial, and protozoan diseases.
• soft-bodied ticks (Ornithodorus) are vectors of endemic relapsing fever
(caused by Borrelia duttoni) and Q-fever.
• Control of ticks:
• Repair of cracks.
• Insecticide spraying on floors and cracks.
• Infested animals are dusted by insecticide agents or dipped in special
solution.
• In endemic areas: wear light-colored, tightly woven slacks and a long
sleeved shirt; spray clothing with an insect repellant containing N,Ndiethyltoluamide
Insects
Insects have three body
sections:
 the head, thorax, and
abdomen;
 three pairs of legs, all
attached to the thorax;
 one pair of antennae.
 they may have one or two
pairs of wings.
 The mouthparts of insects
are elaborate.
 There are two principal
kinds of metamorphosis in
insects: simple and
complete.
Insects
• Class Insecta is divided into 4 orders of
medical importance:
• 1. Order Anoplura (lice).
• 2. Order Siphonaptera (fleas).
• 3. Order Hemiptera (bugs).
• 4. Order Diptera (mosquitoes and flies).
Order Anoplura (lice)
• Order Anoplura (lice). Body is flattened dorsoventrally.
• Lice are wingless insects with short legs.
• Order Anoplura displays incomplete
metamorphosis.
Head louse
• Morphology (Pediculus humanus):
• Adult louse is 2-5 mm in size, male is smaller
than female.
• Body is divided into head, thorax and abdomen.
The head louse found
on humans is specific
to people. It can’t be
contracted from the
family dog, cat or any
other animal.
Mammals and birds
can have lice but they
are species specific.
• These are insects that
CANNOT jump or fly.
• Their method of
movement relies on 6
legs, each of which ends
in a claw which can
grasp human hair.
Lice
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Life cycle.
- Female louse lays about
10 eggs daily.
Eggs are cemented to
hairs or to fibers of clothes.
Eggs hatch in about one
week.
Nymphs feed on blood
and pass through 4 instars.
Adult louse emerges in
about two weeks.
Transmission of Head Lice
• Host-to-host (direct contact from
someone who is infested)
• By wearing infested clothing
(hats, scarves, coats, hair
ribbons etc.)
• By using infested combs, or
brushes
• By lying on a bed, couch or
carpet that has recently been in
contact with an infested person.
• Head Lice are NOT known to transmit
pathogens (germs). They are a nuisance
but NOT a health hazard.
Disease transmission (body louse).
Epidemic typhus caused by Rickettsia
provaceki, Trench fever. Epidemic relapsing
fever
• Lice don’t mount expeditions, striking off to
find new heads. They are obligate human
parasites, their goal is to stay on the head
where they presently live!!!!!
Order Siphonaptera (fleas)

About 2500 species, most parasites of mammals
only approx. 100 species on birds

Temporary obligate parasites, blood-feeding exclusively
as adults

Most fleas of medical and veterinary importance are not
host species-specific
increases the potential for acquisition and
transmission of pathogens
Flea Life Cycle
Flea eggs
Adult fleas
Important Flea Species
Xenopsylla cheopis (Oriental rat flea) - primary urban
plague vector
Pulex irritans (human flea) - occasional epidemic plague
vector
Ctenocephalides felis, C. canis, - cat and dog flea - primary
pest species
Tunga penetrans – sand flea (chigoe)
Parasitic Flies
Order Diptera
Flies - Diptera
• The key
distinguishing adult
structure : two
wings.
• All Flies are
Holometabolous
(having a complex
metamorphosis
– i.e. egg, larvae
pupa, and adult)
One of Great Adaptations of of Flies - The
Habitat of larval stage
 The habitat of the larval
stage is basically
“aquatic or semiaquatic,” and they have
adapted to live in very,
very “challenging”
environments.
Allows them to invade
Dead and Living tissues
Diptera – Flies as parasites
• Ectoparasites
1. Adults are free
living but blood
feeding with the
larvae stages
aquatic or in moist
semi-aquatic
habitats.
(Nematocera and
Brachycera)
Diptera – Flies as parasites
2. Adults
ectoparasites (or
blood feeding) but
larvae develop
within female and
essentially pupate
after emerging
from mother
(Glossina,
Hippoboscidae)
Diptera – Flies as parasites
• Endoparasites
3. Adults free living
but larvae are
internal or partially
internal (flesh
feeding) parasites
of vertebrates
(Oestrus,
Gasterophilus,
Cochliomyia
hominovorax)
Gasterophilus intestinalis
Myiasis Defined
The invasion of organs and tissues of
humans or other vertebrate animals with
dipterous larvae, which for at least a
period feed upon the living or dead tissue
or, in the case of intestinal myiasis, on the
host’s ingested food.
Metallic Flies
 Cochliomyia hominivorax
Lucilia spp.
Calliphora spp.
Musca domestica.
Housefly is a medium-sized fly, 6- 10 mm
in length; the female is generally slightly
larger than the male.
Distribution: cosmopolitan.
Morphology. Adult fly has a gray color.
Body is divided into head, thorax, and
abdomen.
Life cycle. 1. Eggs are laid into masses of
decaying organic substances, garbage,
refuse or manure.
2. Larvae hatch in 6-24 hours and feed on
organic matter.
3. They molt 2 times giving 3 larval stages.
4. The third larva pupates inside the larval
skin.
5. The adult emerges after a few days .The
whole cycle takes about one week.
House fly
4th vein angled
4 dark stripes
Red eyes
 Breeding media
 Garbage
 Decaying fruit or
vegetables
 Decaying meat
 Human or animal fece
 Grass clippings
Medical importance
1. Indirect mechanical transmission of
microorganisms (as typhoid, poliomyelitis
and bacillary dysentery), eggs of helminthes
and cysts of protozoa.
2. Accidental myasis.
Control
1.Sanitary disposal of refuses, garbage and
manure (breeding media) by dumping,
burning or application of insecticides.
2.Control of adult flies by screening or space
spraying of insecticides.
Mosquitoes
• Bloodfeeding - only females
take blood
• Males feed on plant sugars
• Gonotrophic cycle - feed, egg
development, oviposition
(half-gravid, gravid)
Disease transmission
Some species of Anopheles
transmit: 1. Human malaria
2. Wuchereri bancrofti
Some species of Culex
transmit
1. Wuchereria bancrofti
2. Encephalitis
3. Rift valley fever
Differences between Anopheles and Culex.
Eggs – 3 strategies
• Singly on water surface
– Anopheles
• Singly in a pile, on moist substrates
– Aedes/Ochlerotatus
• Form of a raft, on water surface
– Culex
– Culiseta
Larval Stage – Growth Stage
• Larval instars (4)
• Aquatic, Filter feeders
• Respiration
Anopheles
Pupa – Lighter than water
• Non-feeding
• Respiration
Pupal Stage Comparison
Anopheline
Culicine
Mosquito Pupa and Larvae
Mosquito Emerging from Pupal
Exuvia
Adults
Emergence
Mating
Feeding
Adult Stage Comparison
Culicine
Anopheline
Culex
Anopheles
Aedes aegypti
Thank you for
attention !