Medical Entomology

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Medical Entomology
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MEDICAL IMPORTANCE OF ARTHROPODS

• 1)As aetiologic agents (causes) of diseases.
• Tissue damage
• Induction of hypersensitivity reactions.
• Injection of poisons
• Entomophobia (acarophobia)
• 2) As vectors of diseases
• I Mechanical transmission - simple carriage
  of pathogens.
• II Biological transmission
• - cyclical
• - propagative
• - cyclopropagative
• III Transovarian transmission

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Important arthropod vectors for human diseases
House fly (Musca domestica) Mechanical transmission of many viruses, bacteria and parasites.
Mosquitoes Anopheles malaria filariasis Culex filariasis, viruses Aedes yellow fever, dengue fever, Rift Valley Fever
Lice Body louse vector for Relapsing fever, typhus and trench fever.
Fleas Rat flea is vector for plague due to Yersinia pestis.
Ticks Soft ticks , some are vestors for Borrela duttoni Hard ticks Include vectors for Babesiosis (protozoa), Q fever, and Rocky mountain spotted fever
Tse tse fly (Glossina) Vector for African Trynanosomiasis (African sleeping sickness)
Black fly (Simulium) Vector for Onchocerca (river blindness)
Sand fly (Phlebotomus) Vectors for leishmania and sandfly fever virus.
Cyclops Vector for Dracunculus medinensis
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HOUSE FLY
Musca domestica
World-wide distribution Body with 3 visible
parts, 3 pairs of legs 1 pair of visible
wings. Retracted mouth parts Breeds in soil and
dirt Not a blood sucker. Mechanical transmission
of many diseases viruses, bacteria and
parasites
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Myasis summary

• Caused by a large number of flies. Common in
  rural areas where people are in close contact
  with animals.
• Eggs or first stage larvae are deposited on body
  apertures, wounds or introduced into unbroken
  skin. Larvae develop causing tissue damage.
• Pathology and Clinical picture depends on type
  of fly, location in body and number of maggots.
  Skin ulcer, aural, nasal or eye lesions.
• Diagnosis by identification of maggot.
• Treatment surgical removal.

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Myiasis
Classification

• Obligatory larvae normally develop within or on
  living tissues of vertebrates e.g.
• Nasopharyngeal (i.e., relating to or affecting
  nose and pharynx) cavities of herbivorous
  mammals,
• Cutaneous and subcutaneous tissues,

Facultative larvae developing in decomposing
organic materials or the necrotic tissues of
living animals
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Myiasis
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Myiasis life-cycle
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Myiasis
- Larva of human botfly, Dermatobia hominis,
manually expressed from furuncle
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Mosquitoes
Cosmopolitan , more than 3000 species. Larval and
pupal stages always aquatic Mouth parts in female
adapted to piercing and sucking blood. Genus and
species distinguished by morphology of adult and
deveopmetal stages.
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Anopheles stephensi
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Phlebotomus ( sand fly
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Phlebotomus ( sand fly
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Simulium damnosum (black fly) Vector of
Onchocerciasis ( river blindness)
Black in colour with hump back and short strong
legs. Short antennae and short strong mouth
parts. Breed in fast running stream of water ,
rich in Oxygen . Diurnal activity. Vector of
river blindness (onchocerciasis).
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Tse tse fly (Glossina spp)
Breeds in forests of central Africa. Body with 3
visible parts, 3 pairs of legs 1 pair of visible
wings. Mouth parts well developed for
sucking blood. Vector of African sleeping
sickness.
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Cyclops vector for Dracunculus medinensis
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Fleas
Wingless ,brown, laterally flattened, 3 pairs of
well developed legs for jumping   Diseases
Xenopsylla cheopis- rat fleaplgue, murine
typhus. Pulex irritans
Rat flea
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Fleas
Rat flea
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LICE Pediculus humanus humanus (P.h.corporis)
body louse Pediculus h. capitishead
louse Morphology 2-3mm long dorsoventrally
flattened   Life Cycle Head or body lice
transferred by contact with infested person or
clothes . Females deposit eggs on the hair
(nits)Eggs hatch after 10 days -----nymphs-------m
aturation in 2 wks . Larvae and adults feed on
human blood. Diagnosis nits are visible by
naked eye , they fluoresce under UV light (Woods
lamp for screening). Pathology Pedicolosis
,irritation and pruritus. Body louse is vector
for Relpsing fever, Typhus Trench fever.  
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Life cycle of the head louse ( Pediculus humanus
capitis )
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Nits of Pediculus humanus

• Pediculus humanus

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Pediculus humanus
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Phthirus pubis
Phthirus pubis (pubic louse or crab louse)
Smaller than Pediculus. (about2 mm) Infests
pubic hair mainly. Transmitted by direct contact
with infested person or clothes. Life cycle
30-40 days.Irritant , no disease transmission.
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Phthirus pubis
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Treatment of Lice infestation

• Removal and decontamination of clotheses 50 C,
  dry cleaning
• Application of preparations containing permethrin
• Removal of nits by fine comb

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Bed bugs (Cimex lectularius)
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Bed bugs (Cimex lectularius)
Bed Bug, small, flat, oval bloodsucking insect,
with a reddish-brown color, reduced wings, and an
unpleasant odor. The common bed bug infests
houses, particularly beds. It hides during the
day and feeds at night, sucking the blood of
humans and other mammals. Two to four generations
are produced yearly, depending on the temperature
and the food supply. The other species of bed
bugs feed on bats and certain birds.
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Bed bugs (Cimex lectularius)
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Triatomid bug , vector of Chagas disease(
American trypanosomiasis)
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Scorpions

• Highly venomous
• Thick-tail scorpions (family Buthidae). They have
  thick tails and thin pincers.

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Scorpions

• Non-venomous
• Thin-tail scorpions (families Scorpionidae,
  Ischnuridae). They have thin tails and broad,
  well developed pincers.

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Scorpions
Local scorpions in KSA include
The yellow scorpions (Leiurus quinquestriatus),
The black scorpion (Androctonus crassicauda).
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This is a preparation containing the F(ab')2
fraction of the immunoglobulins raised against
scorpion venoms. The antivenom is prepared by
hyperimmunizing healthy horses using gradually
increasing doses of local scorpion venoms and
immunomodulators .
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TICKS
Body 1 segment
4 pairs of legs no antennae
no
wings
Hard Ticks Babesiosis, Q fever, Rocky Mountain
spotted fever
Soft ticks Relapsing fever
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• Brown Dog Ticks
• A. Engorged Female
• B. Female
• C. Male
• Black-Legged Ticks (Deer Ticks)
• D. Larvae
• E. Nymphs
• F. Males
• G. Females
• H. Engorged Female

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Scabies
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Scabies
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Scabies
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Scabies
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Scabies
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Scabies
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Scabies
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Scabies
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Bee stings
BEES  Venoms of bees are a mixture of enzymes and
several polypeptides some of which are
pharmacologically active e.g. histamine or
neurotoxic. Some people are hypersensitive to
venoms and suffer anaphylactic reaction , death
might result in 1 hour.
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Latrodectus hasseltii (The Red-back Spider) This
spider is commonly found outdoors and around
human habitation. It's often called The Red-back
spider. A bite from a hasseltii is highly
venomous.
Hobo or Brown Recluse Spider A venomous bite
from a can cause severe necrotic arachnidism
results from envenomation (venom poisoning). It
occurs due to the venom's ability to clot blood
that results in an area of tissue receiving
inadequate blood flow and thus dying secondary to
oxygen starvation.