Medical arthropods

Mohieddin M Abdul Fattah

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Arthropods

Crustacea

(cyclops)

Chelicerata

Ticks, mite, scorpion

Insecta

Flies, bugs, fleas & lice

Body segments

2;cephalothorax and abdomen

2; cephalothorax- non segmented abdomen

3; head, thorax and abdomen

Legs -wings4 pairs4 pairs 3 pairs – 1 or 2 pairs

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Life cycle:•Flies and mosquitoes and fleas: Egg larva pupa adult•Lice and Bugs: Egg nymph adult.•Tick and mites: Egg larva nymph adult.•Cyclops: Egg several larval stages adult

Arthropodes

• Arthropod can be:• Pathogen or parasite: a disease-

causing organism• Host or Reservoir : an organism

infected by a pathogen or parasite• Vector: an invertebrate organism that

carries disease causing organisms from one host to another

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How do insects affect human health?A. Permenant parasites of human tissues:1. Myiasis (larvae of non-biting flies)2. Tungiasis By Flea Tunga penetrans3. Pediculosis by lice4. Scabies by mite Sarcoptes scabeii.B. Nuisance as temporarily biting parasitesC. Allergenic: mite (Dermatophagoides) induces

allergy.D. Envenomization Tick poisoning, scorpiones,

spiders.E. Vectors that transmit microbial agents: viruses,

Rickettsia, Bacteria, protozoa and helminthes. 4

How insect vectors transmit infectious diseases

A. Mechanical transmission:• Vectors act as passive carrier of the

microbes. • Microbes adhere to body parts or pass

unchanged through the digestive tracts of the insects.

B. Biological Transmission (4 types):1. Propagative.2. Cyclopropagative.3. Cyclodevelopmental.4. Transovarian.

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Biological transmission?A. Propagative: The microbe multiplies in the

arthrpodes without cyclo-morphological development

• (Viruses, Rickettsia, Bacteria).B. Cyclopropagative:The microbe multiplies in the

arthrpodes with cyclo-morphological development • (Protozoa; Plasmodium, Leishmania,

trypanosomes).C. Cyclo-developmental: The microbe undergoes

vital cyclo-morphological development , but does not multiply.

• Helminthes; filaria, Hymenolepis, and Dipylidium.

D. Transovarian: microbes transmitted vertically from adult to the offspring through ovary. 6

Medical Importance of insects

• Name the induced diseases.

• Name the causative agent of each.

• Mention the type of transmission.

• Mention how the agent exits the arthropod and how it enters the human host.

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Medical importance of flies

• Non biting flies (Musca domestica)A. By Mechanical transmission 1. Typhoid fever: Bacteria; Salmonella typhi.2. Amoebic (Entameba histolytica) and bacillary

(Shigella dysenteries).3. Cholera (Vibrio cholerae).4. Conjunctivitis (Haemophylus sp)5. Hepatitis: Hepatitis A virus and poliomyelitis

(polioviruses).B. By direct invasion of tissues1. Myiasis: tissue invasion by larvae of flies.

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Medical importance of biting flies• All transmissions by bit ( anterior station)A.Plebotomus (Sandfly):1. Harara by irritating saliva 2. Leishmaniasis (Leishmania) by cyclopropagative T. 3. Sandfly fever (virus) by propagative T. 4. Oroya fever (Rickettsia: Bartonella) by propagative T.B.Simulium Blackfly: 1. Onchocerciasis (O. volvulus) cyclo-developmentally. C.Chrysops. 1. Loiasis (Loa loa) by cyclo-developmental T.D.Glossina (Tsetse fly): 1. African trypanosomiasis (T. brucei) by cyclo-

propagative.

Medical importance of insects• Kissing bugs:

1. American trypanosomiasis: Trypanosoma cruzi.

• Fleas:

1. Plague; Bacteria (Yersinia pestis).

2. Endemic typhus (Rickettsia mooseri),

3. Hymenolepiasis: Hymenolepis nana and diminuta.

4. Dilepidiasis: Dipylidium caninum.

5. Dermatitis due to hypersensitivity to flea’s saliva.6. Tungiasis (Chigger): Tissue invasion by Tunga flea.

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Medical importance of insects

• Lice: 1. Epidemic relapsing fever (Borrelia recurrentis).2. Epidemic typhus (Rickettsia prowazeki).3. Trench fever (Bartonella quintana).4. Pediculosis: tissue invasion.• Mosquitoes: 1. Malaria (protozoa; Plasmodium)2. Elephantiasis: Wucheria bancrofti,3. Yellow fever (virus).4. Dengue fever (virus)

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Medical importance of insects• Ticks: 1. Rocky mountain spotted fever (Rickettsia rickettsii).2. Q fever (Rickettsia; Coxiella burnetii).3. Endemic relapsing fever Bacteria (Borrelia. duttoni).4. Babesiosis: Protozoa; Babesia5. Tick paralysis (salivary envenomization)• Mites:1. Liponyssoides: rickettsialpox (R.acari) 2. Trombicula: o Scrub typhus fever: Rickettsia orientaliso Dermatitis: allergy to saliva excreted during bite. 1. Demodex folliculorum: acne like lesion (tissue invasion).2. Sarcoptes scabeii: scabies (tissue invasion).3. Dermatophagoides: bronchial asthma and allergic

rhinitis. 12

Medical importance of arthropodes

• Cyclops:

1.Diphyllobothriasis: D. latum.

2.Sparganosis: D. mansonoides.

3.Dracontiasis: Dracunculus medinensis

• Cyclo-developmental transmission.

• Through accidental ingestion of cyclops.

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