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Medical arthropods

Mohieddin M Abdul Fattah

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Arthropods

InsectaFlies, bugs, fleas &lice

ChelicerataTicks, mite, scorpion

Crustacea(cyclops)

3; head, thorax andabdomen

2; cephalothorax- nonsegmented abdomen

2;cephalothoraxand abdomen

Bodysegments

3 pairs – 1 or 2pairs

4 pairs4 pairsLegs -wings

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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

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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 fromone 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.٤

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How insect vectors transmitinfectious diseases

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

microbes.• Microbes adhere to body parts or pass

unchanged through the digestive tracts ofthe 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-morphologicaldevelopment

• (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 doesnot multiply.

• Helminthes; filaria, Hymenolepis, andDipylidium.

D. Transovarian: microbes transmitted verticallyfrom adult to the offspring through ovary. ٦

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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 thehuman host.

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Medical importance of flies• Non biting flies (Musca domestica)A. By Mechanical transmission1. 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 saliva2. 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.١٢

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Medical importance ofarthropodes

• 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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