This document discusses various parasites that can infect humans, including their characteristics, life cycles, and methods of transmission. Some key points: - Parasites include ectoparasites that live on the host surface and endoparasites that live inside the host. Obligatory parasites are permanently adapted to parasitic life while accidental/facultative parasites can live freely or depend on a host. - Examples of ectoparasites discussed are fleas, lice, bed bugs, and ticks. Endoparasites include intestinal pathogens like Entamoeba histolytica and the malaria parasite Plasmodium. - Many parasites are transmitted by arthropod vectors like mosquitoes, sand flies,

1. MEDICAL ENTOMOLOGY

2. Parasitism
• A relationship between species, where one organism, the parasite,
lives on or in another organism, the host, causing it some harm, and
is adapted structurally to this way of life.

3. Parasite
• is an organism which lives either within (endoparasite) or upon
(ectoparasite) another organism.

4. Parasite may be
• Accidental parasite: is an organism that establishes itself occasionally in an unusual host
(hosts that they do not normally parasitize) e.g. dog roundworm.
• Facultative parasite: is an organism which can live either free or depending on the host for
breeding. e.g. Callophorida larva
• Obligatory parasite: is an organism which is completely and permanently adapted for the
parasitic life. e.g. Plasmodium
• Incidental parasite: normally lives on a definitive host but may be found on other hosts
sometimes.
• Specific parasite: which occurs in a particular definite host. i.e. there is specifity in the host
parasite relationship. e.g. Taenia solium.

5. The obligatory parasite may be
• Temporary parasite: parasite which only visits its host for blood meals
e.g. Mosquitoes
• Periodic parasite: parasite which passes a definite part of its life
cycle in a host. e.g. sheep bot fly Oestrus ovis.
• Permanent parasite: which passes all its life in a host. e.g. Adult
Shistosoma sp.

6. Ectoparasites
• Live on the surface of the host.
• They can be temporary, or
permanent.
• Respiration is aerobic.
• Specialization has led to loss of
fewer structures, e.g., wings in
fleas, bedbugs and lice.
Endoparasites
• Live in the body of the host.
• They are generally permanent
parasites.
• Respiration is often anaerobic.
• Specialisation has led to the
loss of several structures, e.g.,
digestive organs in Taenia.

7. Host:
is an animal that harbors a parasite
The host may be:
• Intermediate host: which harbors the larva or asexual stage of
parasite.
e.g. Man in malaria life cycle
• Definitive host: which harbors the mature stages or the sexual
stages of the parasite. e.g. Mosquitoes in malaria life cycle.
• reservoir host: is any host other than man which harbors the
parasite.

8. Pathogen: is the parasite responsible of the disease condition or the
causative organism.
Vector: is an arthropod carrier of a pathogen.
Enteric disease: is an intestinal pathogen.
Endemic disease: is a pathogenic disease found in a definite locality in a
permanent way.
Epidemic disease: is the sudden appearance of a pathogenic disease in
any locality.

9. Methods of disease transmission
• Mechanical disease transmission
• Biological disease transmission
• Propagative
• Cyclo-developmental
• Cyclo-propagative
• Trans ovarian transmission

10. Class: Insecta (Hexapoda)

12. Cockroaches (Order Dictyoptera)

15. Entamaeba histolytica

17. Bedbugs
Order Hemiptera: Family Cimicidae
Cimex lectularius

19. Triatomine bugs
Order Hemiptera
Family Reduviidae
Subfamily Triatominae

24. Lice
Order Anoplura
Families Pediculidae and Phthiridae
• Body louce Pediculus humanus corporis
• Head louse Pediculus humanus capitis

28. Louse-borne Typhus
Epidemic Typhus
Causative Organism:
Rickettsia prowazekii var. prowazekii

29. Human infection may be acquired from an infected
louse by:
• Deposition of the louse’s faeces on the brocken skin.
• Transfer of infective faeces on soiled fingers to the conjunctive.
• Crushing the louse on the broken skin.
• Injection of the louse’s saliva into the skin.
• Contaminating mucous membranes with dried louse’s faeces in which the
Rickettsias can survive for months.
• Inhaling air-borne rickettsias.
• Transferring the rickettsias liberated from a crushed louse into the mouth
(i.e. infection through the mucous membrane of the mouth).
There is no reservoir host in this type of typhus.

30. Symptoms
• Fever
• Severe headache
• Pain in the backs and legs
• Lack of feeling
• Tremors
• Insomnia
• Rash
• In severe cases: death may occur

31. Relapsing fever
Causative Organism:
Borrelia recurrentis

32. Pathology and symptoms
• Sudden rise of temperature (40-41◦ C)
• Severe headache
• pain in the back, joints, liver and spleen
• Haemorrhage from the skin and mucous membranes are common
• The conjunctive has a jaundice appearance. The temperature lasts 4-5
days, and then drops suddenly with abundant sweating and weakness
but relief from pain.
• After an interval of 5-14 days, a second febrile attack develops, usually
slightly less severe and shorter than the first one. In untreated patients,
as many as ten attacks and remissions may occur before there is
cessation of symptoms.

33. Human infection takes place only when the
louse is crushed on the skin.

34. Pediculosis
Vagabond’s disease

36. Order Diptera

37. Family Culicidae
• Anopheles species are primarily of medical importance as vectors of
human malaria (Plasmodia spp.) but they are also vectors of
filariasis (Wuchereria bancrofti, Brugia malayi and B. timori) and
certain arboviruses.
• The genus Aedes contains important vectors of yellow fever,
dengue, encephalitis viruses and many other arboviruses, and also
vectors of W. bancrofti and B. malayi.
• Certain Culex species transmit W. bancrofti and a variety of
arboviruses.

39. Order Diptera
Family Culicidae
Subfamily Anophelinae
Anopheles sp.

42. Symptoms
•Fever
•Tiredness
•Vomiting
•Headache
•Seizures

43. Order Diptera
Family Culicidae
Subfamily Culicinae
Culicine mosquitoes
• The subfamily Culicinae contains 30 genera of mosquitoes, of which the
medically important ones are:
• Culex
• Aedes
• Mansonia
• Sabethes
• Haemagogus
• Psorophora

44. Culex pipiens

48. Aedes sp.

52. Phlebotomine sandflies
Order Diptera
Family Phlebotominae
e.g. Phlebotomus papatasi (Sand flies)

53. Leishmaniasis
• Cutaneous leishmaniasis is the most common form. It causes an
open sore at the bite sites, which heals in a few months to a year
and half, leaving an unpleasant-looking scar.
• Mucocutaneous leishmaniasis causes both skin and mucosal ulcers
with damage primarily of the nose and mouth.
• Visceral leishmaniasis or kala-azar ('black fever') is the most serious
form, and is potentially fatal if untreated.
Symptoms include fever, damage to the spleen and liver, and anemia

56. Order Diptera
Family Simuliidae
Blackflies

59. Horseflies
Order Diptera
Family Tabanidae
The Tabanidae

62. Order Diptera
Family Muscidae
The common housefly
Musca domestica

63. • By flies’ contaminated feet, body hairs and mouthparts.
• By flies vomiting on food during feeding, which they do
frequently.
• By defecation, which often occurs on food. This is
probably the most important method of transmission.

64. Entamaeba histolytica

66. Order Diptera
Family Glossinidae
Tsetse flies
Glossina

67. There are 3 methods of transmission of trypanosomes in
Glossina:
1. Mechanical transmission
2. Contaminative
3. Cyclical

69. Myiasis
The invasion of organs and tissues of man or vertebrate animals
with dipterous larvae
• Cutaneous, dermal or subdermal myiasis
• Urinogenital myiasis
• Ophthalmic myiasis
• Nasopharyngeal myiasis
• Intestinal or enteric myiasis.

70. Cutaneous Myiasis

72. Types of Myiasis
• Accidental
• Obligatory
• Facultative

73. Family Calliphoridae

74. Family Sarcophagidae

76. Fleas
Order Siphonaptera

78. 1. Plague caused by Pasteurella pestis. It is transmitted by Xenopsylla
cheopis. The flea transmits the bacillus from rat to rat or from rat to man.
On cutaneous inoculations, the bacilli produce inflammation to the
lymphatic giving bubonic plague.
2. Murine typhus produced by Rickettsia prowazeki var. moseri.
3. Flea dermatitis.
4. Chigger’s disease is caused by invasion of the skin by fleas. The gravid
female burrows in the skin and engorges itself. This leads to the formation
of an ulcer.
Fleas may cause and transmit the following

79. Plague
Pasteurella pestis

80. Symptoms
• Fever
• Headache
• Chills
• Weakness
• One or more swollen, painful lymph nodes
• Extensive dark red spots of the skin and mucous
membrane in fatal cases.

81. Male and female flea may transfer the bacilli to a
healthy host in one of the following ways
• Following an interrupted feeding the flea may regurgitate blood
and bacilli into the puncture wound of the next host.
• Bacilli multiply in the intestine of the flea and may be deposited
in faeces in or near wound caused by the flea.
• Multiplication of the bacilli in the flea mid gut may produce a
block of blood rendering the flea unable to obtain blood into its
mid gut. Consequently, the flea wanders from one host to another
trying to feed and inoculating the new hosts with the bacilli.

82. Murine typhus
Rickettsia prowazeki var. mooseri

83. Symptoms
• Fever
• Chills
• Body aches
• Muscle pain
• Loss of appetite
• Nausea
• Vomiting
• Stomach pain
• Cough
• Rash

84. Infection takes place:
• Through the flea faeces
• By crushing the flea into a puncture wound

85. Insects with urticating hairs
(Lepidoptera)

86. Order Hymenoptera

87. Order Coleoptera
Blister or vesicant beetles

91. Symptoms
• Fever
• Headache
• Rash
• Nausea
• Vomiting
• Stomach pain
• Muscle pain
• Lack of appetite

92. Transmission
• By tick bites
• Exposure to crushed tick tissues, fluids, or tick faeces
• Transovarian transmission

93. Family Argasidae
Soft Ticks

95. Tick-borne relapsing fever
•Vector: soft ticks
•Causative organism: Borrelia sp.
•Transmission: Tick bite
•Symptoms include:
headache
muscle and joint aches

96. Scabies mites