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General - Parasitology πŸͺ± > L4: Medical Entomology > Flashcards

L4: Medical Entomology Flashcards

1
Q

What is the classification of arthropods?

A

Class insecta and class arachnida

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2
Q

What are the characteristics of class Insecta?

Body:
Wings:
Legs:

A

Head, thorax, abdomen

Present or absent

Three pairs (Hexapoda)

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3
Q

What are the characteristics of class Arachnida?

Body:
Wings:
Legs:

A
  • Cephalothorax, abdomen - one mass
  • Absent
  • Four pairs (Octopoda)
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4
Q

What is the medical importance of arthropods?

A
  1. Arthropods as disease agents:
    - Dermatitis by the insect bite e.g., lice, mosquitoes.
    - Inoculation of poisons e.g., ticks.
    - Tissue invasion Sarcoptes scabiei (Scabies), larvae of flies (myiasis).
    - Entomophobia: abnormal fear when seeing an arthropod (e.g., Spiders).
  2. Arthropods as vectors for transmission of diseases agents, by:
    - Mechanical transmission (Passive carrier), e.g. Typhoid fever by Musca fly.
    - Biological transmission (Part of its Life cycle), e.g. Plague by Fleas
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5
Q

What are the general characters of mosquitos?

A

οƒœ One pair of wings.

οƒœ The female mouth is adapted for piercing & sucking of blood. Male feed on nectar.

οƒœ Complete metamorphosis [Egg (on water surface) β€”> Larva (aquatic) β€”> Pupa (aquatic) β€”> Adult].

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6
Q

What is the medical importance of mosquitos? ( female transmits)

A

οƒœ Human malaria (Anopheles spp.)
οƒœ Lymphatic filariasis (Culex spp.) (elephantiasis is due to Normal mosquito)
οƒœ Yellow fever, dengue fever (Aedes aegypti)

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7
Q

What are the methods of control of Mosquitos?

A

οƒœ Physical control: Elimination of breeding places, bed nets, wire screening of doors and windows.

οƒœ Biological control: Natural enemies such as frogs, Gambusia affinis fish.

οƒœ Chemical control: Insecticides (Paris green as poison for larvae, DDT), repellants (Citronella oil).

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8
Q

What are the general characters of flies (Musca domestica)?

A

οƒœ The adult fly is 6-10 mm long, grey in color. One pair of wings.

οƒœ Mouth parts are soft, retractile, adapted for lapping and sucking fluids.

οƒœ Complete metamorphosis [Egg (on ground) β€”> Larva β€”> Pupa β€”> Adult].

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9
Q

What is the medical importance of flies?

A
  1. Mechanical transmission of Viruses, Bacterial & Parasites disease (e.g., protozoa cyst & helminths eggs).
  2. Accidental myiasis.
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10
Q

What are the methods of control of flies?

A

οƒœ Health education and sanitation.
οƒœ Fly nets.
οƒœ Insecticides e.g. DDT & Pyrethrum.

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11
Q

What are the general characters of lice (pediculus spp.)?

A

οƒœ Small insect 2-4 mm, wingless. Permanent ectoparasites.

οƒœ Mouth parts are adapted for piercing and sucking blood in all stages.

οƒœ Incomplete metamorphosis [Egg β€”> Nymph β€”>Adult]

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12
Q

What are the names of lice infesting man?

A

οƒœ Pediculus humanus capitis (head louse).

οƒœ Pediculus humanus corporis (body louse).

οƒœ Phthirus pubis (pubic louse): sexually transmitted parasite.

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13
Q

What is the medical importance of lice?

A
  1. Head Lice (more common) cause itching and dermatitis (NOT known to transmit pathogens but stimulates its invasion).
  2. Pediculosis (vagabond’s disease) by all types: severe dermatitis, skin becomes thickened hyper-pigmented skin.
  3. Vector of diseases (body louse): as  Epidemic typhus.
     Epidemic relapsing fever.  Trench fever.
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14
Q

What are the methods of treatment and control of lice?

A

οƒœ Heath education and good hygiene. Frequent bathing.
οƒœ Topical pediculicides (Permethrin lotion 1%, Benzyl alcohol).
οƒœ Oral ivermectin.
οƒœ Wet combing of hair (to remove eggs). Washing clothes and bed lining in boiled water

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15
Q

What are the general characters of fleas?

A

οƒœ -Small, bilaterally compressed. Brown in color, with no wings.

οƒœ -Mouth is adapted for piercing and sucking of blood.

οƒœ - Complete metamorphosis (Egg β€”> Larva β€”> Pupa β€”> Adult).

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16
Q

What is the medical importance of fleas?

A

1- Plague:

  • It is an acute severe bacterial disease.
  • Fleas act as vectors and transmit them to humans;
  • It is an acute infectious disease caused by bacteria (Yersinia pestis) which is transmitted from human or rats to human by fleas.
  • e.g., Pulex irritans (Human flea), Xenopsylla cheopis (rat flea).

2- Endemic typhus feve (Rickettsial infection). Fleas act as vectors and transmit them to humans.

3- Flea dermatitis: Itching due to biting followed by a 2ry bacterial infection.

17
Q

What are the methods of control of fleas?

A
  1. Sanitation: Vacuuming of carpets and furniture.
  2. Boiling of cloths and linings.
  3. Application of insecticides as Pyrethrins or Insect growth regulators sprays for indoor and infested pets.
  4. Flea traps
18
Q

What are the general characters for ticks?

A
  • The body is one mass sac-like.
  • The mouth is adapted for piercing and sucking. (In all stages)
  • Metamorphosis is gradual (Egg β€”> Larva (6L)β€”> Nymph (6L)β€”> Adult)

. - Ticks are classified into 2 families:
 Ixodidae (hard ticks).  Argasidae (soft ticks).

19
Q

What is the Medical importance of ticks?

A
  1. Diseases transmitted by ticks:
    a) Bacterial diseases: e.g., Lyme disease.
    b) Viral disease: e.g., Viral meningoencephalitis fever.
    c) Protozoal diseases: e.g., Texas cattle fever.
  2. It causes Dermatitis.
  3. It causes Tick Paralysis.
    - It is produced by some toxins in the saliva of the tick;
    - it produces a blockage of the neuro-muscular junctions of the spinal cord. (When it is near the CNS)
    - Paralysis disappears after the removal of the causative tick.
20
Q

What is the treatment and control of tick paralysis?

A
  • By the removal of the tick after covering the tick with ether or gasoline oil.
  • Control: Spraying insecticides on the floors, in cracks in the walls
21
Q

What are the important members of mites causing diseases to man?

A
  1. Sarcoptes scabiei.
  2. Demodex folliculorum.
  3. House dust mites (HDMs).
22
Q

What are the general characters of Sarcoptes scabies?

A
  • It is a small mite (200-450 ΞΌm), grey (like flies) in color, oval in shape (itch mite).

β€’ It has 4 pairs of legs as adult & nymph
and 3 pairs of legs as larva.

  • Skin disease, worldwide, increase in poor hygiene & over-crowded areas.
  • Mouth is adapted for tearing the tissues.
  • Metamorphosis is gradual like lice and ticks (Egg Larva Nymph Adult).
23
Q

What is the habitat of Sarcoptes scabiei and its life cycle?

A

οƒœ Skin: It lives in intracutaneous tunnels of thin skin between fingers, wrist, back of the hands, elbows, axillae, breast, umbilicus, back, bends of the knee, groin, buttocks, and external genitalia.

οƒœ The head and neck are not affected.

οƒœ The female burrows tortuous tunnels in the skin epidermis and deposits eggs.

οƒœ both larvae and nymph are found in hair follicles.

οƒœ Maturity occurs after two weeks from the deposition of the eggs

οƒœ The larvae and nymphs move freely over the skin and are found in hair follicles.

24
Q

What is the mode of infection by Sarcoptes scabiei?

A

By contact with an infected person or contaminated clothes and sexual contact.

25
Q

What are the clinical manifestations of scabies?

A

οƒœ The activity of mites usually occurs at night. It is activated by the warmth of the affected part.
The characteristics are :

  1. Mites produce tortuous tunnels, dark in color due to the toxins secreted and their excretions
  2. Severe itching occurs that interfere with the sleep (insomnia)
  3. Scratching and secondary bacterial infection occur on top, resulting in vesicles and pustules.
26
Q

What is crusted scabies(Norwegian scabies)?

A

οƒœ Crusted Scabies: (Norwegian Scabies):

  • it is a severe form that can occur in immunosuppressed individuals.
  • high numbers of mites are present in keratotic lesions all over the body.
  • highly infective.
27
Q

What is another name for scabies?

A

β€œseven years itching”

28
Q

What is the diagnosis of scabies?

A

I. Clinically:

  • history of severe itching during the night,
  • its sites distribution in the skin,
  • by finding the scratches, vesicles, and pustules.

II. Laboratory:

  • skin scraping of intracutaneous tunnels or lesions
  • rapid microscopic examination of the specimen by using Dermoscope.
29
Q

What is the treatment of scabies?

A

1- Application of scabicidal:
- to the skin from the neck downwards,
- for 8-12 hours then washed. Repeated application is usually needed.
- Examples are:
 Benzyl benzoate emulsion or cream (25%)
 Pyrethrum cream 5%
 Sulfur- lanoline suspension 5-10%

2- Ivermectin is given as a single oral dose, also as a topical application.

3- Frequent bathing.

4- Antihistaminic for itching. Antibiotics for secondary infection.

5- All members of the family must be treated.

30
Q

What is the prevention and control of scabies?

A
  1. Treatment of infected patients.
  2. Boiling of internal clothes and bed linen.
  3. Personal hygiene as frequent bathing.
  4. Avoid contact with infected patients
31
Q

What are the general characters of Demodex folliculorum?

A

It is the hair follicle mite. It is very minute and elongated.

32
Q

What is the habitat of demodex folliculorum?

A
  • It lives in the hair follicles and sebaceous glands particularly of the face around the nose, eyelids, and mouth.
33
Q

What is the mode of infection of Demodex folliculorum?

A
  • It is transmitted by direct contact with the patient or by using polluted towels.
34
Q

What are the clinical manifestations of Demodex follicolurum?

A
  • It causes :
     acne, blackheads
     dermatitis and blepharitis.
35
Q

How is Demodex follicolurum diagnosed?

A

Squeeze out the contents of the blackhead or sebaceous gland and examine under the microscope for the adult and its stages.

36
Q

What is the treatment of Demodex follicolurum?

A
  • Sulphur ointment 15% or Benzyl benzoate 25%.

- Oral Ivermectin (like lice)

37
Q

What are house dust mites?

A
  • These are found in dust on the floors, furniture, mattresses, and beds.
  • House dust mites contain allergens that produce allergic reactions in humans.
38
Q

What are the clinical manifestations of house dust mites?

A

They cause :
 allergic rhinitis,
 conjunctivitis,
 dermatitis and bronchial asthma.

39
Q

What is the prevention and control of house dust mites?

A
  1. Exclusion of dust from bedrooms and furniture of sensitive individuals.
  2. Cleaning of carpets, beds, and furniture using a vacuum cleaner

General - Parasitology πŸͺ± (5 decks)

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