Download 05-Insecta lecture

‫بسم هللا الرحمن الرحيم‬
Class Insecta
Arachnida
Hexapoda
Octapoda
Crustacea
Body:
Head, thorax, abdomen
cephalothorax& abdomen
Antenna
one pair
Absent
Wings
:
two pairs
Absent
Legs
:
three pairs
4 Pairs
cephalothorax&abdomen
2 pair
Absent
4-5 of appendages
Medical importance of
arthropods:
1.arthropods as disease
agents.
2.arthropods as vector for
transmission of disease
Medical importance of arthropods:
arthropods as disease agents:
1- dermatitis and allergic skin lesion caused
by the insect bite e.g. lice ,mosquitoes.
2- Inoculation of poisons
( ticks, scorpions ,spiders).
3-Tissue invasion
larvae of flies (myiasis),Sarcoptes scabiei.
4-Entomophobia:
abnormal fear occurs when
seeing an arthropod (Scorpion)
Arthropods as vectors of diseases:
It transmit disease agents by:
1- Mechanical transmission:
Arthropods acts as passive carrier
of the
disease agents.
2- Biological transmission:
Arthropod plays an essential role in
transmission.
3- Transovarian transmission
From infected insect to off spring
(through ovary).
1- Mechanical transmission:
The arthropods acts as passive
carrier of the disease agents,
 without any multiplication or cycle
development inside arthropods.
 occurs by contamination, causative
agents are carried on the mouth
parts, legs or hair of non biting
arthropods.
e.g. house fly.

2- Biological transmission:
a) Propagative
b) Cyclo-developmental
c) Cyclo-propagative
2- Biological transmission:
The arthropod plays an essential role
in transmission , in which the disease
agents undergo certain changes:
a) Propagative :
Organisms multiply inside the vector
without cyclical changes.
e.g. Yersinia pestis in the flea
,yellow fever virus in Aedes aegypti .
b) Cyclo-developmental
Organisms undergo developmental
changes inside the vector but
without multiplication
e.g. microfilaria of Wuchereria
bancrofti in culex.
-one M.f. give one wuchereria
adult
c) Cyclo-propagative:
Organisms multiply and
undergo developmental changes
inside the vector :
- Malaria parasites in Anopheles,
- Leishmania parasites in Sand fly.
3- Transovarian
transmission Organisms are
transmitted from infected
mother to off springs through
the egg
e.g. Rickettsia in
mite
Development of arthropods:
- Complete metamorphosis :
immature stages are totally
different from adults
(egg—larva –pupa—adult).
- Incomplete metamorphosis :
immature stage (nymph )
resembles adult, differs only in
being smaller in size and sexually
immature (egg—nymph—adult)
Class Insecta
Arachnida
Hexapoda
Octapoda
Crustacea
Body:
Head, thorax, abdomen
cephalothorax& abdomen
Antenna
one pair
Absent
Wings
:
two pairs
Absent
Legs
:
three pairs
4 Pairs
cephalothorax&abdomen
2 pair
Absent
4-5 of appendages
Class Insecta




Mosquitoes
and
-Anopheles -Culex,
-Aedes
- Phlebotomus -Chrysops
- Simiulium
Fleas
Lice
Bugs
flies
- Musca -Stomoxys
- Glossina
Oestrus, Calliphora,
Hypoderma,Lucillia
Dermatobia,Sarcophaga
Gastrophilus,
Wohlfahrtia
10h
Mechanical transmission of
diseases



Viruses
: Hepatitis, poliomyelitis.
Bacterial : Enteric fever, bacillary dysentery,
wound infection and trachoma.
Parasitic : Mechanical transmission of
Eggs : Ascaris ,Trichuris,
Hymenolpis nana…
Cysts : Entameba histolytica, Giardia
Myiasis:
infestation by fly larvae.
 Eggs
or first stage larvae are
deposited on apertures, wound or
introduced into unbroken skin causing
tissue damage
 Common in rural area where people
are in close contact with animals
Pathology :



depend on
type of fly
location in body and
number of maggot
Myiasis



Obligatory : larvae normally develop
within or on living tissues of
vertebrates
Facultative :larvae develop in
decomposing organic materials or in
necrotic tissues of living animals.
Types of myiasis recognized in
humans include urogenital,
gastrointestinal, ocular, auricular,
and cutaneous (anatomical).
 Diagnosis
:
identification of maggot.
 Treatment : surgical removal
In KSA there is several reports
of myiasis
- cutaneous –myiasis
Cordylobia anthropophaga
- ophthalamo-myiasis
Oestrus ovis
lesion:
•- At the site of penetration there
is red papule that gradually
enlarges.
•- At first slight itching pain that
increases in intensity as the lesion
develops into a furuncle.
•- The furuncle's opens, permitting
fluids containing blood and waste
products of the maggot to drain.

Although flesh-eating dipteran
larvae can be successfully used to
debrief necrotic tissue from
wounds under controlled medical
conditions, potentially can damage
healthy tissue and produce severe
psychological distress in victims
Mosquitoes
Mosquitoes
Mosquitoes
Mosquitoes
 Cosmopolitan,
more than 3000
species.
 Larvae and pupal stages always
aquatic.
 Mouth
part in female adapted to
piercing and sucking blood.
 Genus and species are
distinguished by morphology of
adult and developmental stages.
 Life
cycle
Egg—larvae–- pupa--- adult.
 Anopheles vector of malaria and
filariasis, breed in clear water
 Culex vector of filariasis and
viruses, breed in polluted water
(cities)
 Aedes vector of yellow fever,
dengue fever, rift valley fever.
malaria
filariasis
RVF: virus cause illness in cattle, sheep
and sometime man.
- s.s : fever, headache, joint and muscle
pains, nausea, sweating and photophobia.
- In sever cases purpura, hematemesis
melaena ,fatal encephalitis retinitis and
hepatitis
 Dengue fever
Viral disease like influenza 7 days
Yellow fever

RVF
 Aedes
mosquitoes may acquire RVF
from feeding on infected animals.
 Virus pass transovarial to eggs, so
new generation of infected mosquitoes
hatch from infected eggs.
 This eggs may survive for several
years in dry condition.
 In rainy season ,eggs hatch and
spread virus to animals on which they
feed.
Yellow fever
Quarantinable viral disease
 s.s.: high fever hepatomegaly,
jaundice hemorrhages and albuminurea
due to necrotic lesion in liver and
kidney.
 Vaccination is obligatory.
 Transmission of virus is
propagative in mosquitoes.

Sand flies
Phlebotomus spp
Live in warm climates
 Minute, hairy ,with wing kept erect
while resting.
 Breed in crack of soil and wall,
rubbish heaps
 Move in hops rather than fly .
 Nocturnal ,during day time rest in
cool damp places
 Vector of leishmaniasis, sad fly
fever.

Sand fly
Vector for Leishmaniasis
L.Donovani -visceral leishmaniasis.
 L. tropica
-cutaneous leishmaniasis.
 L.braziliensis -mucocutenous.
Transmission cyclopropagative.
 Sand fly fever viral disease
mild fever like influenza propagative

L.Donovani -visceral leishmaniasis
L. tropica
-cutaneous
leishmaniasis
L.braziliensis
-mucocutenous leishmaniasis.
Tse tse fly
Glossina
Tse tse fly Glossina spp
Breeds in forests of central Africa.
 Body with visible parts.
 3 pairs of legs.
 1 pair of visible wings.
 Mouth parts well developed for sucking
blood (male and female suck blood).
vector of African sleeping sickness.
 Causetive organism : polymorphic
Trypanosomes cyclopropagative transm.

Simulium
 Black
in colour with hump back and
short strong legs.
 short antenna and short strong
mouth parts.
 Breed in fast running stream water
,rich in oxygen.
 Diurnal activity.
 Vector of river blindness
(onchocerciasis)
Simulium
introduce infective
larvae of Onchocercus volvulus
during bite.
 Tissue nematode-cutenous filaria
 Adult male and female in s/c nodules
 M.f. in skin and eye causing
river blindness.
 Cyclical
transmission
Chrysops
vector of Loa loa
- (eye worm)
- Calabar swelling
Chrysops (deer fly) is a vector
for transmission of loa loa.
 Diurnal periodicity.
 In Africa.
Pulex irritance
Ctenocephalides canis
Rat flea
Pulex irritans
Xenopsylla cheopis
Medical importance of fleas
1- Transmision of Plague
Caused by bacterial bacilli Yersinia
pestis which block fleas gut,
hungry fleas leave dying rat to
feed on any animal (man) causing
infection to new host.
(Xenopsylla cheopis-rat flea )
(propagative transmission)
 Bubonic
plague lymphadenopathy
with suppuration especially in
inguinal and axillary region
 Pneumonic plague allow direct
spread
 Septicemic plague
2- Transmision of Typhus
fleas born typhus endemic or murine
typhus Rickettsia mooseri organism
colonize endothelium of small blood
vessel .
s.s. fever ,headache insomnia skin
rash in sever case ischemia and
gangrene.
3- Flea nuisance
4- Shigoe flea Tunga penetrance
skin disease chigger (Jegger)
disease
 Tunga
 also
penetrans,
known as the 'Jigger' or
'Chigoe' flea, occurs in tropical
Africa, Americas and western
India.
 The adult female flea burrows
into human flesh, particularly the
feet. the ovaries will swell and
eggs are produced, with the body
becoming around the size of a
pea.
Tunga penetrance
This is an adult female Tunga penetrans that was
surgically removed and measures 4.8mm. The
head & thorax can be seen as the dark brown
stucture, off centred and to the lower left.
Pediculus humanus
Obligatory –permanent
ectoparasites.
 Leave host when temperature
increase (fever) or decrease
(death) thus transmitted infection
from person to another.

Pediculus humanus capitis head
louse
- Pediculus humanus humanus
(P.h.corporis) body louse
-
Transmitted by direct contact with
infected person or clothes
 life cycle 30 days. Irritant.
 Nymph, larvae and adult feed on
human blood.
 Diagnosis
:
- nits visible by naked eye, and
fluoresce under UV light
(wood's lamp for screening).
 Treatment
- Removal and decontamination of
clothes (laundry at 50 degree).
- Preparation containing permethrin
- Removal of nit by comb.
disease transmission:
lice act as a vector for
- Epidemic typhus
- Epidemic relapsing fever,
- Trench fever.
Pediculosis, irritation and pruritus.
Epidemic typhus
Caused by Rickettsia prwazeki-organisme
taken with blood to epith. of insect gut
multiply inside the cell which rupture and
organism pass with faces .
 Infection when Ricktissia contact m.m. of
mouth or conjunctiva .
 Rickettsia colonize endothelium of blood
vessel
 s.s. fever, skin rash ,headache and
insomnia .ischemia and gangrene in sever
case.

 Trench
fever
5 days fever caused by Rickettsia
quintana.
Sever pain in muscle and joint last
1-2 days and reoccur after 5days.
 Epidemic
relapsing fever
- Borrelia recurrentis
organism present
in body fluid not in feces of lice.
- Febrile period re-occur one or two
time mortality can be high.
•Smaller than Pediculus,
about 2mm.
•Infest pubic hair mainly
and eye lashes.
•Transmitted by direct
contact with infected
person or clothes
•life cycle 30-40 days.
Irritant .
•No disease transmission
Phthirus pubis
Bed bugs (Cimex lectularius)
 Bed
bugs (Cimex lectularius)
 Brown,
wingless ,dorsoventral
flattened.
 Adult-eggs-nymph ,adult.
 Only irritant ,not disease vector
 Large
insect ,
 small narrow head
with strong mouth
parts ,and antenna
 laterally spotted
abdomen
 vector of American
trypanosomiasis
(chaga`s disease)
Bee
Venoms of bee are
mixture of enzymes and
several poly peptides e.g.
histamine or neurotoxin.
some people are
hypersensitive to venom
and suffer anaphylactic
reaction ,death might
result in one hour.
Class Arachnida
(Octapoda)
Scorpion
 Spiders
 Ticks (hard &soft)
 Mites
-Sarcoptes scabiei
-Dust mites

Scorpion
 Cephalothorax
with
median and lateral
eyes ,pedipalps,4
pair legs.
 anterior and
posterior abdomen
end with stinger
Scorpion
scorpion feed on insects
 Never sting unless attacked by man when
bare foot and hand come in contact with
scorpion hidden in clothes and shoes.,
Pathology
Local sever pain, inflammation, tissue
necrosis
 General nausea ,vomiting, sweating ,itching
 Sever case muscular spasm convulsion and
shock with heart failure

Scorpion contain
variable amount of
neurotoxins
hemolysins enzymes,
cardiac toxin ..
 These produce local
and general systemic
effect

 First
aid : cold compress, and
analgesic (Aspirin, Paracetamol) to
relieve pain and transport to a
hospital.
 Monitor vital functions :
cardiac , CNS and respiratory
functions and treat as required.
◦ antivenom for severe systemic
envenomation.
◦ tetanus toxoid to prevent infection
◦ antihistamine and steroids for
allergic reaction to antivenom
◦ adrenaline for anaphylactic
reaction,
◦ atropine to control excessive
secretions.
◦ IV calcium gluconate for relief from
pain and cramps
 Local
treatment :
- Immobilize and clean wound
- Envenomation of the eyes must be
flushed with water or any bland
fluid.
 Don't.
◦ 1. Do not use traditional rules
such as incisions, suction,
tourniquet or the application of
ointments.
◦ 2. Do not administer antivenom
(spider or snake) if no signs or
symptoms of severe envenomation
presents itself.
◦ 3. Do not administer barbiturates,
opiates, morphine or morphine
derivatives as this could greatly
increase convulsions and cause
respiratory distress.
Venomous spiders
-Latrodectus spp is
prevalent in tropics and
subtropics.
-It causes systemic
anachridism due to toxic
effects of venom.
-Some spiders (Ioxosceles)
may produce local tissue
necrosis ,this called necrotic
anachridism,
Ticks
Body one segment
4 pair of legs
No antennae
No wings
Soft Tick
Hard tick
 Hard
tick hard cuticle
 Soft
tick soft cuticle
-
babesiosis,
Quneensland fever,
Rocky mountain spotted fever,
tick paralysis
- Relapsing fever Borrelia duttoni
- Tick paralysis
Mites
Sarcoptes scabiei
 Itch mite cause scabies and mange in
animals, cosmopolitan.
 Infection by :Direct contact with infected
person or his clothes.
Life cycle
Female burrow in epidermis and deposit
eggs
 Eggs hatch in 3-4 days, larvae excavate
new burrow and maturate in 4 days

Pathology

- Intense itching
- delayed hypersensitivity reaction,
secondary bacterial infection.
Diagnosis: scrapings from skin lesion
examine for mites and eggs.
Treatment:
Eurax or
 emulsion of benzyl benzoate of all body
from chin down.
 Gamma benzene hexachloride (lindane)

Preferred
sites interdegital, popliteal fold and groin
- Mites vector for

Scrub typhus ( Leptotrombidium)

Rickettsial pox
- Rickettsial disease (R. Orientalis)
- Adult and nymph are free living
- larvae feed once ,when infected larvae
growing to adult female pass organisms
transovarian in deposited eggs
- Larvae of next generation become
infective through its single bite.
Mild disease –week before onset firm red
papule appear at site of mite bite forming
black eschar.
-
Causative agent of scabis
Rickettsial pox
Class Crustacea
Water fleas (Cyclops)
Cyclops (water flea)
•Aquatic arthropod
•Cephalothoraxe & abdomen
• 2 antenna
•Swimming appendages
• Vector for:
Dracunculus medinensis
‫الحمد هلل‬
 Losses
due to nagana are
estimated at $ 1.5 - 4 billion
annually ,
 estimated to be 500 000 new
cases of human sleeping sickness
with 45 000 deaths annually
(WHO)





After inoculation, Rickettsiae proliferate
intracellularly in the endothelium of small
blood vessels.
Endothelial damage results in focal occlusive
endangiitis in small venules and arterioles.!).
In this way a generalised, multifocal, multiorgan vasculitis occurs.
This can lead to thrombosis and vascular
occlusion, possibly with oedema and local
necrosis.
every organ in the body can be affected,
the symptoms are extremely diverse..
chigger (Jegger) diseas