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MOSQUITOES

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  1. MOSQUITOES If you would see all of Nature gathered up at one point, in all her loveliness, and her skill, and her deadliness, and her sex, where would you find a more exquisite symbol than the mosquito? -- Havelock Ellis, 1920

  2. HISTORY • Ancient Rome • Scotland • Middle ages and Henry II • Ancient India and Mesopotamia • Ancient China • Egypt • Alexander the Great 323 B.C. • Genghis Khan and Western Europe

  3. Alexander TheGreat • General, King, Ruler • Babylon 323 B.C. • Malaria? • WNV? • Typhoid?

  4. European Exploration • European exploration of new lands. • Defensive and Offensive diseases. • Offensive germs in the New World. • Indigenous destruction • Slave trade • 1890’s and beyond…

  5. The Family Culicidae - Mosquitoes • Worldwide distribution • > 3450 species and subspecies (38 genera) • Great habitat diversity • Approximately 40 million years older than humans (fossils from Eocene, 38-54 mya) • Anophelinae (subfamily) - Anopheles (genus) • Culicinae (subfamily) - Aedes, Culex, Haemagogus, Mansonia, Ochlerotatus and all other genera

  6. Mosquito Characteristics • Conspicuous proboscis - forward projecting • Scales on thorax, abdomen, legs & wing veins • A fringe of scales along the posterior margin of the wings

  7. Mosquito Characteristics (note conspicuous forward projecting proboscis) Non-biting Gnat (note proboscis curved under head) Mosquito Gnat

  8. Bloodfeeding - only females take blood Males and females feed on plant sugars Gonotrophic cycle - feed, egg development, oviposition (half-gravid, gravid) Egg biology - oviposition location, type of egg, desiccation resistance, diapause Larval biology - aquatic, spiracle for breathing, filter-feeders, some cannibalistic, variable habitats Mosquito Characteristics

  9. (1) Eggs – 3 strategies • Singly on water surface • Anopheles • Singly in a pile, on moist substrates • Aedes/Ochlerotatus • Form of a raft, on water surface • Culex • Culiseta

  10. Mosquito eggs: Culex egg raft Anopheles egg with ‘floats’ Aedes egg Patterns on the external egg surface are species specific

  11. Egg stage comparison

  12. CULEX Egg Raft

  13. (2) Embryonation – 2 options • Eggs hatch immediately (not all) • OR • Diapause required • Triggered by decreasing day length. • **Egg stage over wintering stage** • Aedes/Ochlerotatus

  14. (3) Larval Stage – Growth Stage • Larval instars (4) • Aquatic, Filter feeders • Respiration Anopheles

  15. (4) Pupa – Lighter than water • Non-feeding • Respiration Pupal Stage Comparison Anopheline Culicine

  16. Mosquito Pupa and Larvae

  17. Anopheles Pupa and Larvae

  18. Mosquito Emerging from Pupal Exuvia

  19. (5) Adults • Emergence • Mating • Feeding Adult Stage Comparison Anopheline Culicine

  20. females Comparison of male and female Anophelines vs. Culicines Culicine Anopheline males

  21. Behavior • Activity • Host Specificity • Zoophilous • Anthropophilous • Ornithophilous

  22. HABITAT

  23. Medical Importance • Biting Nuisance (annoyance) • Arboviruses • Numerous (Yellow Fever, Dengue Fever, WNV, JE, SLE, EEE, WEE, VEE). • Filariasis • Bancroftian and Brugian filariasis. • Malaria • 4 plasmodium species

  24. Malaria History • Ronald Ross (1897) • Malaria Eradication? • Between 350 and 500 million clinical episodes of malaria occur every year. • 1-2 million deaths occur every year. • About 60% of the cases of malaria worldwide and more than 80% of the malaria deaths worldwide occur in Africa south of the Sahara.

  25. HUMAN MALARIA • Parasite – Plasmodium spp. • P. falciparum, P. vivax, P. malaria, P. ovale • Vector – Anopheles spp. • Host • Reservoir • Distribution

  26. Anopheles gambiae WHO/TDR/HOLT Studios, 1992

  27. Global Distribution

  28. Distribution • Distribution Model

  29. Distribution • Endemic / Epidemic Risk Areas

  30. Distribution • Duration of Malaria Transmission Season.

  31. Distribution Start / End of Transmission Season

  32. Distribution • Population Distribution

  33. Filariasis History • Patrick Manson (1877) • Worked in Taiwan • Autopsies in China • Threadlike worms • “Nothing walks with aimless feet.:”

  34. Mosquito-Borne Human Filariasis • 250 million infections each year • 2-3 million cases of obstructive filariasis • 20% of pop in Calcutta infected • 2 diseases that affect humans • Urban Disease • Rural Disease

  35. Urban and Rural Disease • Urban Disease (Bancroftian filariasis) • Parasite – • An anthroponosis • Bancroftia • Rural Disease (Brugian filariasis) • Parasite – • An anthroponosis or zoonosis • Brugian

  36. Transmission • (1) Microfilariae in blood. • (2) • (3) Microfil. Penetrate midgut  thoracic muscles. • (4) • (5) Enter new host.

  37. Periodicity • (1) Periodic Infection • (2) Subperiodic Infection

  38. VECTORS • (1) Bancroftian Filariasis • Cx. pipiens quinquefasciatis • Cx. pipiens pipiens • Anopheles spp. • Aedes spp. • (2) Brugian Filariasis • Anopheles spp. • Aedes spp. • Mansonia (genus)

  39. DISTRIBUTION • Tropics and subtropics • Wuchereria bancrofti is encountered in _________________. • Brugia malayi is limited to _____. • Dog Heartworm (Dirofilaria immitis, D. repens)

  40. Mosquito Arboviruses • Intrinsic incubation period of a virus in humans is a few days. • Host becomes viraemic. • Viraemia lasts typically 3 days then disappears from the peripheral blood. • An arthropod must bite a viraemic host if it is to become infected.

  41. Yellow Fever History

  42. Yellow Fever • Brought to U.S. via slave trade. • Aedes aegypti • Originally in New World Monkey populations • Jungle Yellow fever (3-factor disease in monkeys) • New World people bring to town • Old World mooting monkeys bring to town. • Does occasionally occur in U.S. • 1964 Eradication program (U.S. Public Health)

  43. YELLOW FEVER • Is a _______ • Prevented the building of the Panama Canal. • Pathogen: • Vector: Aedes aegypti, Aedes spp., Haemagogus • Host:

  44. Reservoir • Human-mosquito in urban cycle, • Monkey-mosquito in forest cycle; • Deforestation may force infected monkeys into areas where human-mosquito transmission can occur.

  45. African Yellow Fever Transmission Cycle Vectors: • Ae. Africanus (sylvatic) • Ae. Bromeliae (rural) • Ae. Aegypti (urban) • Transovarial Transmission