This document provides an introduction to medical entomology. It defines key terms like entomology, medical entomology, vectors, and discusses the importance of studying medical entomology. The document covers taxonomy of arthropods including classification of insects. It describes insect anatomy and life cycles. It explains how arthropods can affect human health by transmitting diseases, causing annoyance through bites, and discusses methods of disease transmission. The document emphasizes the importance of understanding arthropod vectors to control diseases and protect public health.

1. I N T R O D U C T I O N T O M E D I C A L E N T O M O L O G Y
University of Burao
faculty of medical laboratory
course; medical entomlogy
lecturer: Bashir S. Adem
(BSC, MA)

2. At the end of this lecture, you should able to:
 Define entomology ?
 Medical vs. Veterinary entomology?
 List common characteristics for the identification of
arthropods
• Explain briefly taxonomy of arthropods
• Describe biological functions of arthropods
• Explain importance of arthropods
 Anatomy of insects
 General life cycle

3. What is entomology ?
 The study of insects is termed entomology.
 Medical entomology is a specialization that involves
the study of those insects that are of medical
importance, for example mosquitoes, flies, lice and
fleas.
 However, the term medical entomology is usually
used in a broader sense to take into account the
arachnids, a group of invertebrates that includes ticks
and mites,
 And others that may be considered medical
importance.

4. Cont..
 An insect can be defined simply as a small, six-legged
animal.
 Vector: a carrier of disease. For example, in malaria a
mosquito is the vector that carries and transfers the
infectious agent.
 Of the million kinds of animals that scientists have
described and named, more than 800,000 are insects.
Around 7,000 to 10,000 new kinds of insects are discovered
every year.
 Insects live almost everywhere on earth – from steamy
tropical jungles to cold polar regions, from snow-capped
mountains to deserts below sea level.

5. Cont..
 The study of insects is called entomology.
 The study of insects includes their development,
 anatomy,
 physiology, life history,
 behavior, environment,
 and classification.
 Entomologists, the people who study insects, observe,
collect, rear, and experiment with insects.
 Why should we spend time studying insects?
 Why is entomology important to us?

6. Medical VS Veterinary?
 Medical entomology: is the study of insects,
insect-borne diseases, and other associated problems
that affect humans and public health.
 Veterinary entomology: is the study of insects
and insect-related problems that affect
domestic animals, particularly livestock and
companion animals (dogs, cats, horses, caged birds,
etc.).

7. Vector (biology)?
 Traditionally in medicine, a vector is an organism
that does not cause disease itself but when spreads
infection by conveying pathogens from one host to
another.
 In that time , we call, vector biology
 Species of mosquito, for example, serve as vectors for
the deadly disease Malaria.

8. Medical entomology terms?
 Class Chilopoda (Chila = margin, poda = foot;
centi = hundred, pes, pedis = foot):
 It is the class of Arthropods commonly called as
Centipedes means a hundred legs which are
carnivorous.
 Class Diplopoda (diplo = two, poda = legs): It is
the class of phylum Arthropoda having 2 pairs
of legs in each segment commonly called millipede
means a thousand legs found in dark and
humid places.

9. Cont..
 Arthropod: any member of the phylum
Arthropoda, the largest phylum in
the animal kingdom,
 which includes such familiar forms as lobsters, crabs,
spiders, mites, insects, centipedes, and millipedes.
 About 84 percent of all known species of animals are
members of this phylum.

10. Historical
 Some sort of insects such as fleas, flies and lice, and
ill health of man has been recognized from antiquity.
 Many of man's common ectoparasites are referred
to in religious texts such as the Talmud, Koran
and Bible.
 it was only during the nineteenth century that
any definite proof emerged concerning the role
of insects and other arthropods in the transmission
of disease.

11. Cont..
 in 1868 Fedtschenko discovered that the guinea
worm (Dracunculus medinensis) underwent its
early development in a small copepod (Cyclops).
 it later being shown that man becomes infected by
drinking water containing these infected
crustacea.
 During the same year Melnikoff found cysts in the
body of the dog.
 the flea, was not discovered until some twenty years
later.

12. Cont..
 The most influential discovery of this period,
however,was that made by the physician and
parasitologist Patrick Manson.
 In 1 8 77 while working in China he discovered that
bancroftian filariasis( Wuchereria bancrofti)
underwent development in mosquitoes, Culex pipiens
fatigans ( = C. quinquefasciatus).
 This provided the first real evidence that a
pathogenic organism of man underwent obligatory
 development in an insect, and can therefore be rightly
regarded as representing the 'birth of medical
entomology'.

13. Cont..
 During the next 5o years or so a variety of insects,
 ticks and mites were incriminated in quick
succession as vectors of diseases to man and
animals, such as malaria,
 sleeping sickness, yellow fever, typhus, plague and
relapsing fever.
 The rapid advances in understanding how these
diseases were spread allowed the development
 of rational methods of control.

14. Classification of insects
Classification Malarial mosquito
Kingdom animal
Phylum Arthropoda
Class Diptera
Order Culicidae
Family Anopheles
Species gambiae, nilli, kingi,
dancalicus, fenstus, smithi

15. Classification of insecta
Kingdom > Phylum > Class > Order > Family > Genus
> Species
 Kingdom=Animal= Phylum=Arthropods
=Class=Insect
 The class hexapoda is divided in two subclasses:
1. Apterygota
2. Pterygota

16. Classification of insecta

17. Apterygote insects
 The first four orders, the Apterygote insects, are
primitively apterous forms with only a slight
metamorphosis;
 they usually moult several times.
 after attaining sexual maturity and the adults have
one or more pairs of appendages.
 Order I. THYSANURA
 Order 2. DIPLURA
 Order 3. PROTURA
 Order 4. COLLEMBOLA

18. Order I. THYSANURA

19. Order 2. DIPLURA

20. Order 3. PROTURA

21. Order 4. COLLEMBOLA

22. Class 2: Pterygote insects
 The subclass Pterygota is divided in two divisions:
 Exopterygota (= insects with a simple
metamorphosis, without pupal stage)
 Endopterygota (= with a complete metamorphosis,
including a pupal stage)

23. Cont..
Order Ephemeroptera Mayflies
Order Odonata Dragonflies and Damselflies
Order Orthoptera Grasshoppers, Locusts and Crickets
Order Dictyoptera Cockroaches and Mantids
Order Grylloblattodea Rock crawlers
Order Phasmida Stick insects and Leaf insects
Order Dermaptera Earwigs
Order Isoptera * Termites
Order Embioptera Web-spinners
Order Plecoptera Stoneflies
Order Zoraptera Zorapterans
Order Psocoptera Psocopterans (Psocids, Booklice)
Order Mallophaga Chewing lice (Biting lice)
Order Anoplura
Sucking lice

24. Cont..

25. General anatomy of insects

26. Cont..

27. General anatomy of insects
 Adult and many immature insects have three distinct
body regions:
 Head,
 thorax,
 and abdomen

28. The head of the insects
 Pair of antennae are found on the head of the pterygote
insects and the apterygote groups with the exception of
the Protura.
 there are three principal components:
 the basal scape :by which the antenna is attached to
the head,
 the pedicel containing Johnston’s organ
 and the flagellum, which is usually long and
annulated which is more it is the flagellum that is
modified.
 Compound eye.
 Simple eye .

29. Cont..

30. Cont..

31. Cont..

32. Cont..
Mouthparts:
 There are five basic components of the mouthparts:
 labrum, or “upper lip”, with a ventral surface called
the epipharynx;
 hypopharynx, a tongue-like structure;
mandibles, or jaws;
 maxillae (singular: maxilla);
 labium, or “lower lip”

33. Cont..

34. Cont..

35. Cont..

36. The Neck and Thorax
 The Neck and Thorax:
 The thorax is the locomotory center of the insect.
 Typically each of its three segments:
 (pro-, meso-, and metathorax) bears a pair of legs,
and in the adult stage of the Pterygota.
 the meso- and metathoracic segments each have a pair
of wings.
 Between the head and thorax is the membranous
neck (cervix).
 Usually supporting the head and articulating it with the
pro-thorax are the cervical.
 this is where pair of legs and wings developed .
 some insects such as fleas and lice lack wings.

37. Cont..

38. Cont..

39. Cont..

40. The Abdomen

41. The Abdomen
The abdomen differs from the head and thorax in that its segments
generally have a Rather simple structure
 they are usually quite distinct from each other, and most of them
lack appendages.
 The number of abdominal segments varies.
 The primitive number appears to be 12, though this number is
found today in only the Protura.
 Most insects have 10 or 11 abdominal segments, but several of these
are reduced.
 The abdominal segments may be Considered to form three groups:
 Pregenital segments,
 Genital segments,
 And post genital segments

42. The Integument
The integument of insects comprises
 the basal lamina
 epidermis
 and cuticle
 The cuticle, which is mainly produced by the
epidermal cells, usually includes three
 primary layers
 the inner procuticle
 middle epicuticle

43. Cont..

44. cuticle?
 The cuticle is an extracellular layer that covers the
complete external surface of insects, as well as the
surfaces of their foreguts and hindguts, and acts
both as a skeleton for muscle attachment and as a
protective barrier between the animal and its
environment.
 The cuticle is an integral part of a complex
dynamic tissue, the integument, which also
includes the cuticle-producing epidermal cells, and
various glands and sense organs

45. Cont..
 epidermis, lies beneath and secretes the cuticle.
 The epidermis plus cuticle together form an
integument.
 cuticle which consists of procuticle or fibrous cuticle
which consists
 exo-cutitcle,
 mesocuticle
 and endo-cuticle and
 with epi-cuticle consists :
 cement layer,
 wax layer.
 It is most outer layer
 The epidermis is closely associated with molting,

46. Sensory organs
 Insect sensory cells are almost always primary sense
cells
 they both receive a stimulus and conduct it to the
central nervous system.
1. Type I sense cells are associated
with cuticle and accessory cells to form the sense organ
2. Type II cells are not
associated with cuticle and always function as
proprioceptors.

47. Skeletal muscles
 Skeletal muscles can be categorized as
 tubular (leg and body segment muscles, and
wing muscles of Odonata and Dictyoptera),
 close-packed (wing muscles of Orthoptera and
Lepidoptera),
and fibrillar (flight muscles of most insects).

48. Respiration?
 Respiration is by means of air entering small
openings termed (spiracles) in the exoskeleton of the
insect's body,
 these lead to tracheae within the body which in turn
branch into small tracheoles
 Then, ramify the body and carry oxygen to the
tissues.
 There may be a pair of spiracles on most body
segments or they may be greatly reduced in number.

49. Digestive system?

50. cont..
 Typically saliva lubricates and initiates digestion of
the food.
 The chemicals that promote feeding
(phagostimulants).
 The gut includes three primary subdivisions, foregut,
 midgut, and
 hindgut,
 Insects have enzymes
 Absorption of digestion products occurs mostly in
the anterior midgut

51. Cont..

52. Life cycle

53. Cont..

54. Cont..

55. Cont..
 Growth is an important part of an individual’s.
 ontogeny,: the developmental history of that
organism from egg to adult.
 Egg =larva = next stage larva= pupa = adult stage.
 The egg stage begins as soon as the female deposits
the mature egg.

56. Cont..

57. Larval or nymphal phase
 Hatching from the egg may be by a pronymph,
nymph, or larva.
 when the young insect is said to be in its first instar.it
is known “instar”.
 This stage ends at the first ecdysis when the old
cuticle is cast to reveal the insect in its second instar.
 All immature holometabolous insects are called
larvae.

58. Cont..
 the development of the immature insect is
characterized by repeated molts separated by
periods of feeding, with hemimetabolous insects
generally undergoing more molts to reach
adulthood than holometabolous insects.
 Immature terrestrial insects with hemimetabolous
development such as cockroaches
(Blattodea),grasshoppers (Orthoptera), mantids
(Mantodea), and bugs (Hemiptera) always are
called nymphs.

59. Larvae
 Immature terrestrial insects with hemimetabolous
 development such as cockroaches (Blattodea),
 grasshoppers (Orthoptera), mantids (Mantodea),
and
 bugs (Hemiptera) always are called nymphs.

60. Why medical entomology?
 Insect and other arthropods can directly affect
healthy by:
 1- Transmitting diseases.
 2- Annoyance to man by their bites.
 3- Poisonous to man.
 4- Severe irritations

61. Cont..
 An insect is said to be a vector when it transmits
pathogens or parasites from one animal to another, or
man to animal.
 Methods of disease transmission
1. Mechanical transmission:
 For example: House flies carry the pathogens on their
hairy legs, feet and bodies.
 vector serves only as mechanical vector.
 Another example of mechanical transmission is the
spread of Trypanosoma evansi amongst horses by the
 contaminated mouthparts of horseflies.

62. Housefly

63. Cont..
 2- Biological transmission
 The pathogens have undergone multiplication andor
development within the insect.
 In addition biological transmission including:
 Transovarial transmission
 Pathogens penetrate the ovaries of vector, result
infected eggs.

64. Cont..
 A simple example is provided by the rickettsial
parasites causing louse-borne typhus which are
swallowed by the body louse when it sucks blood
from a typhus victim.
 The ingested rickettsiae multiply prolifically in the
cells of the insect's stomach, after which they pass
out with the faeces of the louse and man becomes
infected when these are scratched into abrasions
on the skin or inhaled.

65. Activity :
 what are the Advantages arthropods?
 what are the disadvantages of Arthropods?
 List the most famous vectors that are in our
houses?
 and How do we reduce the vector population
from our
1. Houses
2. And our city or urban

66. Advantages and disadvantages of
arthropods
 A. Health Effects:
 Arthropods affect the health and comfort of man in
many different ways.
 The common fear of insects (entomophobia)
 possessed by many people is perhaps the least
serious.
Proper knowledge of the appearance of harmful,
beneficial and harmless arthropods can do much to
remedy these conditions.

67. Cont..
The Following are some examples of the health
effects attributed to arthropods:
• Arthropods attack man, domestic and wild animals.
• They bite and suck blood.
• They pass infective organisms and may inject toxin to
man and animals (mechanically or biologically).
• They cause myiasis (infestation by larva of diptera)
on
man and animals.
• Annoy and irritate man and animals.

68. Cont..
 They cause envenomation by their bite, sting, spines
or by their secretions.
 Which cause swelling, pain, redness, rash, fever,
allergic reactions, blood poisoning, or death in some
cases.
 Arthropods parasitize man, animals and plants: for
example louse, and ticks on animals, and aphids on
plants.

69. Cont..
 Cause accidental injury to sense organs: they enter
the eyes, ears, mouth or nostrils.
• They cause allergic/asthmatic reactions by their odor,
secretions, and by their dead body fragments.
• Crop adulteration is another effect of arthropods due
to their droppings.
 Arthropods cause Entomophobia (fear of insects):

70. B. The Beneficial Effects of Arthropods
 pollonization of plants.
 Silk is produced by insects.
 Honey and wax is the other product of insects.
 Arthropods are very helpful in improving the soil.
 Some arthropods lay their eggs on the larva of other
arthropods, the eggs hatch and the young larvae feed
up on the body juice of the host as a parasite.

71. Cont..
 Arthropods that prey upon and destroy other
animals are called predators. They help to reduce the
number of insects. E.g. spiders, ants, dragon flies.
 Insects are valuable as food for humans and animals.
Chickens and turkeys,
 More than other things insects have served man as
sources for scientific knowledge and technological
innovation.

72. General control methods of arthropods
 The control of medically important arthropods
employs many principles used against pests of
agricultural importance, where as control of
arthropods affecting crops and livestock is
fundamentally guided by economic principles.
 Personal protection: Physical barriers between a
vertebrate and arthropods, chemical barriers that
repel arthropods from actual biting;

73. Cont..
 Local control methods:
1. Hot ash to kill or drive away insects like ants.
2. Hot water against ants, bedbugs, lice, fleas,
3. Certain odorous and sticky leaves
 Chemical control methods:
 Biological control (Bio control):
 Barrier zones and quarantines:

74. References
 m. w. service (1980). A guide to a medical
entomology. THE MACMILLAN PRESS LTD.
London.
 Service. S (1996). Medical Entomology for Students.
Cambridge University Press. UK .
 Gullan. Penny. J and Cranston P s. (2010). An
insect, the outline of entomology.UK
 O. W. RICHARDS (1975).IMMS' GENERAL
TEXTBOOK OF ENTOMOLOGY. (The Chaucer
Press), volume 2.