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Medically important Arthropods
- 1. Medically important Arthropods Presenter– Dr. Sukumar T K
- 2. Arthropods • Invertebrate animalswith jointed legs. • Exoskeleton – chitin. • Segmented bodies. • Bilaterally symmetrical • Tubular alimentary canal with mouth and anus. • Coelom
- 3. Medical anthropodology • Majorityof arthropods are not harmful to humans. • Arthropod related with human health. – Harmful – nuisance, discomfort, bites. – Ectoparasites – live and feed on exterior of host without transmitting germs. – Mechanical transporters. – Vectors .
- 4. • Class Arachnida –Ticks and mites (order Acarina)
- 5. • Class Insecta –True flies (order Diptera) – True bugs (order Heteroptera / Hemiptera) – Lice (order Anoplura) – Fleas (order Siphonaptera)
- 6. Class • Insecta – 3disntict regions – 3 pairs of legs – Wings present – 1 pair of antennae – Segmented abdomen. • Arachnids – 2 regions – 4 pair of legs – No wings – No antennae – Abdomen usually not segmented.
- 7. Metamorphosis • The changein form during an insect’s development is called metamorphosis. • Complete metamorphosis. • Incomplete metamorphosis
- 8. Phylum Arthropoda • ClassCrustaceae – cyclops, crabs.
- 9. • Medical importance –Cyclops are intermediate hosts of the fish tapeworm and Dranculus medinensis.
- 11. • Spiders, scorpions,ticks and mites. • 4 pair of legs • Pedipalps – aid in chewing • Incomplete metamorphosis
- 12. Order Acarina • Onlygroup in Arachnida that sucks blood and serves as vector. • Commonly called • Ticks – Hard tick (family Ixodidae) – Soft tick (Argasidae) • Mite – Trombiculid mite, itch mite, dust mite
- 13. • Medical importance –Tick paralysis – Bite injury – Ixodidae – Borrelia burgdoferi, Babesia microti and Ehrlichia spp. – Soft tick – vectors of endemic relapsing fever and Q Fever.
- 14. • Soft tick –Body is often wrinkled. – Mouth parts are ventral and not visible. – Female and male – same appearance.
- 15. • Hard tick –Body is usually smooth. – An inflexible, dorsal scutum covers the idisoma of the male and the anterior part of the idisoma of female. – Mouth parts are terminal and visible from above.
- 16. • Soft tickslay eggs more than once. – feed in night. • Hard ticks lay eggs only once. – Feed on host for few hrs, in day.
- 17. • Control – Environmentalmanagement – Acaricides – Personal protection
- 18. • Trombiculid mite –Larvae – reddish or orange, 3 pairs of legs. – Adult – bright red, hairy or granular, 4 pairs of legs.
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- 20. • Chiggers –parasitic with low specificity. • Chigger dermatitis – reaction of host. • Scab – raised, reddened wheal with a depressed center. • Scrub typhus • Epidemic haemorrhagic fever??
- 22. • Diagnosis – Recenth/o being to grassy area – Fever, itching papules, scab • Prevention – Eradication of wild weed – Control of rats and mice – DDT – Personal protection
- 23. • Sarcoptes scabiei –Commonly called itch mite. – Causes scabies – Disc shaped with distinctive sculptured lines – Stubby legs – Male – 4th pair has amlulacra – Female – 4th pair terminate in long setae
- 25. • Female burrowsin the skin and lays eggs in sinuous tunnel. • Selects places where skin is thin and wrinkled, between fingers, elbows, feet, etc. • Children – whole body.
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- 28. • Prevention – Aggressivetreatment of infested patients and all close contacts, – Disposal or hot wash-dry sterilization of clothes. – Provision of improved access for personal hygiene and health care – Aggressive control of outbreaks of zoonotic scabies with the potential for human transmission
- 29. – House dustmite - Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei. – Morphology • White – tan • Tiny oval shaped • Covered with striations
- 30. Class Insecta • Lice –Head louse - Pediculous humanus var capitis • Pediculosis – Body louse - Pediculoushumanus var carporis • Epidemic fever, Trench fever, Relapsing fever – Pubic / Crab louse – Pthrius pubis
- 31. • Morphology –Pediculous humans – Greyish, wingless, 3pairs of legs. – Abdomen • Male – V • Female - W
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- 33. Louse – lifecycle
- 34. • Therapy – Managementof pediculosis capitis includes two topical or systemic treatments with pediculocides, 7 to 10 days apart. – Removal of all viable nits by carefully combing wet hair.
- 35. • Pthirus pubis –Smaller – Broad body – Large claws on middle and hind legs.
- 36. • Therapy – Managementincludes initial bathing with soap and water, followed by two topical or systemic treatments with pediculicides, 7 to 10 days apart
- 37. Prevention • Prevention strategies –Combinations of sanitizing the environment. – Eliminating all human reservoirs of head lice in households, apartments, housing complexes, classrooms, and schools.
- 38. • Common preventiveinterventions – avoiding contact with potentially contaminated items – soaking all combs and brushes in isopropyl alcohol or 2% Lysol solution – sanitizing the household environment by high heat cycle washing and drying of all bedding, clothing and headgear
- 40. • Fleas – Oriental/ Tropical rat flea – Xynopsilla cheopis • Plague, Endemic Typhus, Host of Hymenolipis tapeworm. – Northern rat flea – Nasopsylla fasciatus • Endemic typhus – Human flea – Pulex irritans • Skin irritation, Intermediate host of Hymenolepis and Dipylidium tapeworm larvae.
- 41. • Morphology – Brownyellow colour – Body covered with bristles
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- 44. • Bugs – Bedbugs – Cimex lectularius, Cimex hemipterus • Allergy, secondary bacterial infection. – Reduvid bug – Rhodnius, Triatoma, Pastrongylus • American trypanosomiasis ( Chaga’s disease)
- 45. • Diverse inappearance – Piercing & sucking mouth parts – When present, 2 pairs of wings (hind pair reduced) – Incomplete life cycle
- 46. • Identification – Small,apricot-coloured & wingless – Circular body & flattened extensions of prothorax behind eyes
- 47. • Reduvid bug •Identification – Large robust bugs = ambush predators of arthropods – Strong recurved beak for biting • Inject paralytic toxin to subdue prey • Bite very painful to humans • No species in SA usually bite mammals • Medical importance – South American subfamily Triatominae (kissing bugs) • Feed on human & animal blood • Transmit Chagas’ disease
- 48. • Flies – Sandfly– Phlebotomus, Lutzomyia • Leishmaniasis, Bartonellosis, sandflyfever – Black fly/Buffalo gnats - Simulium • Onchocercariasis / river blindness – Tsetse fly – Glossina • African trypanosomiasis – Deer fly/ Yellow fly – Chrysops • Loiasis, Tularemia – Domestic fly – Musca domestica
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- 50. Flies • Morphology – 1pairof membranous fore wings – Hind wings reduced to form halters – Mouth parts – proboscus / piercing like. • Larval – No conspicuous head. – Legless – Slender bodies.
- 53. • Mosquitoes – Anopheline •Anopheles culcifacies – Malaria • Clear, stagnant/ sluggishly moving water. • Rest at an angle to the resting surface.
- 54. – Culicine • Filarial- Culex fasciatus – Stagnant, polluted water – Lymphatic filariasis • J.E - Culex gelidus, Culex tritaeniorhyncus, Culex fuscocephela – Japanese encephalitis
- 55. • Aedes – Aedesaegypti • Urban vectors. • Man made small collection of clear water. • Dusk and dawn biters – Aedes albopictus • Rural vectors • Natural collections of clear water • Dengue, Yellow fever, Chickungunya
- 56. • Mansonia – Ruralvector – Breeds on the undersurface of water plants – Brugian filariasis, transmits Dirofilaria repens.
- 57. • Mosquitoes identification –Long and narrow wings – Anopheles – adults rest with abdomen steep angle to substrate. Larvae rest horizontally to water surface. – Culex and Aedes – rest with abdomen at an angle to substrate. Larvae hang at an angle from water surface.
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- 60. • Egg – Anophelesboat shaped, single and float on water. – Culex cylindrical, laid together – rafts, no float. – Aedes olive shaped, single and bottom of water.
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- 62. References • Meical Parasitology– Ruth Leventhal, Russel F. Cheadle. • Principles and Practices of Infectious Diseases 7th Edition – Mandell, Douglous, Bennet.
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