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vector borne diseases-ASK

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vector borne diseases-ASK

  1. 1. "India lives in its villages" 2/6/2014 1
  2. 2.  Why we took more than 60 years to realize the value of health of rural India (NRHM ) 2/6/2014 2
  3. 3. EPIDEMIOLOGY OF VBDs  Enemy’ size -------------------- potential of its threat 2/6/2014 3
  4. 4. 2/6/2014 4
  5. 5. 2/6/2014 5
  6. 6. YELLOW FEVER 2/6/2014 6
  7. 7. 570 million years 200,000 years 1,170,000 species 2/6/2014 7
  8. 8. SCHEME OF PRESENTATION  HISTORY  BASIC CONCEPTS IN VBDs  WHY VBDs SHOULD CONCERN US  CLIMATE CHANGE & VBDs  CHALLENGES IN VBDS  SUMMARY 2/6/2014 8
  9. 9. HISTORY  WORST SCOURGES OF MANKIND  THREAT TO HUMAN SURVIVAL  KILLED MORE MEN THAN ALL THE WARS  CAHNGED THE COURSE OF HISTORY 2/6/2014 9
  10. 10. History of Medical Entomology: • References to associations between humans and arthropods – historical (Homer and Aristotle, among others, wrote about the nuisance caused by flies, mosquitoes, lice and/or bedbugs.) • Important discoveries: •1700’s - Microscope - Leeuwenhoek •1800’s - Infectious Disease - Koch et al. 2/6/2014 10
  11. 11. History of Medical Entomology • 1877- Manson, --Mosquitoes (Culex pipiens) and filarial worms (Wuchereria bancrofti) • 1891 - Smith & Kilborne, -Tick (Boophilus annulatus) and Texas cattle fever (piroplasmosis) transmission • 1900- Finlay, Reed, Carroll, Agramonte and Lazear, Mosquito (Aedes aegypti) and yellow fever virus • 1895- Bruce- Trypanosomes in cattle blood - 2/6/2014 11
  12. 12. History of Medical Entomology –: • Laveran – MP in blood • 1896- Bruce, Tsetse fly (Glossina sp.) transmission of trypanosomes • 1903- Bruce, Tsetse fly transmission of trypanosomes to humans (African Sleeping Sickness) • Ronald Ross - Anopheles mosquitoes with malaria parasites 2/6/2014 12
  13. 13. History of Medical Entomology - : • Graham, 1902-- Mosquito transmission of dengue virus • Liston, Verjbitski et al., --1895 – 1910-- Fleas and plague • Chagas, 1908--Triatomine bugs and trypanosomes (Chagas disease) • Blalock, 1926--Black flies and onchocerciasis (river blindness) • Mosquitoes and viral encephalitides - Hammon and Reeves, early 1940’s • Ticks and Lyme disease - Spielman, early 1960’s 2/6/2014 13
  14. 14. MALARIA  >10000 years ago Malaria in Africa  19th Century AD- Malaria almost all over the globe  Early 20th Century AD- Millions die of malaria almost all over the world  Early 1950s - Malaria almost disappears from North America and from almost all of Europe; deaths mainly in Africa  1960-70s: Malaria strikes back with vengeance 2/6/2014 14
  15. 15. MALARIA & WARS "The history of malaria in war might almost be taken to be the history of war itself  Col. C. H. Melville, Professor of hygiene, Royal Army Medical College, London (1910) in Ronald Ross's book The Prevention of Malaria. 2/6/2014 15
  16. 16. Cause of Deaths in War War Number Serving in Army Battle Injuries (BI) Disease Non Battle Injuries (DNBI) Arthropod Borne Diseases Civil War (Union) 2,128,948 138,154 221,374 Yellow fever, typhoid, malaria Spanish American War 280,564 369 2,061 Typhoid, malaria World War I 4,057,101 50,510 55,868 Trench fever, malaria, louse borne typhus World War II 11,260,000 234,874 83,400 Malaria, scrub typhus Vietnam 4,368,000 30,922 7,273 Malaria Desert Shield 246,682 98 105 Leishmaniasis 2/6/2014 16
  17. 17. Military Entomology - World War I  By World War I, the connection between insects and disease was well established.  Entomologists (6-8) were commissioned as officers in the Sanitary Corps.  Over 9,600 cases of malaria occurred in troops training in the southern U.S.  Trench fever and louse-borne typhus were the primary arthropod-borne diseases in Europe as troops were often infested with lice. 2/6/2014 17
  18. 18. SCHEME OF PRESENTATION  HISTORY  BASIC CONCEPTS IN VBDs  WHY VBDs SHOULD CONCERN US  CLIMATE CHANGE & VBDs  CHALLENGES IN VBDS  SUMMARY 2/6/2014 18
  19. 19. BASIC CONCEPTS  HIGH TRANSMISSIBILITY.  HOST ANIMALS -----VECTOR-----HUMANS  VECTORS DON’T BECOME “ILL” 2/6/2014 19
  20. 20. Phylum Arthropoda :• Bilaterally symmetrical • Jointed legs • Dorsal heart – open circulatory system • CNS (organized central nervous system) • Striated muscle 2/6/2014 20
  21. 21. Phylum Arthropoda Class Crustacea - lobsters, crabs, etc. Class Chelicerata - spiders, mites, ticks, scorpions, etc. Class Diplopoda - millipedes Class Chilopoda - centipedes Class Insecta - beetles, flies, moths, mosquitoe. 2/6/2014 21
  22. 22. Insect Characteristics THREE distinct body regions: - Head (feeding, sensory, CNS) - Thorax (locomotion, respiration) - Abdomen (feeding, reproduction) 2/6/2014 22
  23. 23. Arthropods & Health • Direct Causes of Disease or Distress • Vectors or Hosts of Pathogenic Organisms • Natural Enemies of other medically harmful insects 2/6/2014 23
  24. 24. VECTOR-BORNE DISEASE CONCEPT ARTHROPOD VECTOR age, abundance, daily activity VERTEBRATE HOST susceptibilty, accessibility, numbers of hosts, daily activity 2/6/2014 competence for pathogen Environmental factors (temp, rain) PATHOGEN amplification, maturation, maintenance in nature 24
  25. 25. INCRIMINATING A VECTOR KOCH'S POSTULATES  ASSOCIATION  SPECIFIC CONNECTION  TRANSMISSION  BIOLOGICAL GRADIENT 2/6/2014 25
  26. 26. ARTHROPOD VECTOR Must be susceptible to infection by pathogen. Live long enough for pathogen to complete multiplication or development. THIS AFFECTS THE transmission rate in nature. 2/6/2014 26
  27. 27. COMPONENTS OF TRANSMISSION CYCLE • A vector must take at least 2 blood meals during its lifetime to transmit a parasite. • Once to acquire the infection. • Second to transmit parasite. 2/6/2014 27
  28. 28. GONOTROPHIC CYCLE. This includes the sequence of 5 steps : 1. searching for a host (questing) 2. blood feeding 3. blood meal digestion 4. egg maturation 5. oviposition 2/6/2014 28
  29. 29. ARTHROPOD ACQUISITION & DEVELOPMENT OF PATHOGENS PATHOGEN+BLOOD INGESTED (ORAL) TISSUE CONCENTRATION (SALIVARY GLANDS, or REPRODUCTIVE SYSTEM) PATHOGEN PASSAGE THRU GUT WALL OR EPITHELIAL LAYER (GUT) PATHOGEN MULTIPLIES OR INACTIVATED (GUT) PATHOGEN TRANSPORT BY HEMOLYMPH TO TISSUES OF VECTOR (HEMOLYMPH) 2/6/2014 29
  30. 30. ARTHROPOD VECTOR Suitable host must be found: Anthropophagic (feed on humans only) endophilic (inside loving) exophilic (outside loving) Zoophagic (feed on vertebrates other than humans) mammalophagic ornithophagic 2/6/2014 30
  31. 31. ILLUSTRATION EXTRINSIC & INTRINSIC INCUBATION PERIODS Mosquito refeeds / transmits virus Mosquito feeds / acquires virus Viremia 0 Days 5 Illness Human #1 2/6/2014 Intrinsic incubation period Extrinsic incubation period 8 12 16 20 Viremia 24 28 Illness Human #2 31
  32. 32. PATHOGEN DEVELOPMENT IN BODY OF VECTOR ARTHROPODS • Propagative transmission- (e.g. viruses, YF, WNV, EEE, etc.) • Cyclo-developmental (e.g. Wuchereria bancroftiBancroftian filariasis) • Cyclo-propagative transmission-. (e.g. malaria, Chagas) 2/6/2014 32
  33. 33. PATHOGEN ACQUISITION BY HOST FROM ARTHROPOD CONTAMINATED MOUTHPARTS HOST INGESTS OR CRUSHES INFECTED ARTHROPOD BACK PRESSURE DIGESTIVE TRACT CONTACT WITH CONTAMINATED BODY SURFACES ESCAPE THROUGH BODY WALL INFECTIVE FLUIDS FROM GLANDS (e.g. tick coxal glands) INFECTED FECES 2/6/2014 33
  34. 34. MODES OF TRANSMISSION VERTICAL TRANSMISSION: Passage of parasites/pathogens from one life stage to next life stage or generation to generation. EGGS PARENTAL GENERATION LARVAE offspring F1 GENERATION ADULT 2/6/2014 OR F2 GENERATION 34
  35. 35. 2 TYPES OF VERTICAL TRANSMISSION: EGGS •Transstadial transmission LARVAE •Transovarial transmission ADULT •Venereal transmission 2/6/2014 35
  36. 36. MODES OF TRANSMISSION HORIZONTAL TRANSMISSION: Passage of parasites/pathogens between vector and host. VECTOR 2/6/2014 HOST 36
  37. 37. “Bridging” mosquito species in yellow fever another infected mosquito species transmits pathogen now to humans “Bridging” PRIMARY VECTOR 2/6/2014 37
  38. 38. Vectorial Capacity is thus, a function of (a)the vector's density in relation to its vertebrate host, (b) the frequency with which it takes blood meals on the host species, (c)the duration of the latent period in the vector, and (d) the vector's life expectancy. 2/6/2014 38
  39. 39. FACTORS THAT STRONGLY AFFECT PATHOGEN TRANSMISSION BY VECTORS  Vector competence (ability to get infected & transmit)  Incubation period in vector (influenced by temperature)  Vector contact with critical host  Population abundance of vector & hosts  Diurnal feeding habits of vector  Pathogen replication in host  Host feeding preferences  Vector longevity  Precipitation – flooding & drought  Temperature  Proximity of vectors/reservoirs to human populations 2/6/2014 39
  40. 40. Mosquitoes and Key VBDs  Responsible for a great VBD burden  Malaria – parasite  Yellow fever – virus  Dengue fever/hemorrhagic fever – virus  Other viral fevers  West Nile, Rift Valley, Bunyamwera  Filiariasis – helminth  Encephalitis – viruses  Western Equine, Eastern Equine, St. Louis, etc. 2/6/2014 40
  41. 41. Flies and VBDs  African sleeping sickness – african trypanosome parasite – tsetse fly bite  Enteric bacteria diseases – houseflies – food contamination  Vibrio cholerae (cholera), typhoid fever (Salmonella typhi), Shigella spp. (bacterial dysentery)  Onchoceriasis (river blindness) – helminth – black fly bite  Sandfly – Kala azar, oriental sore, sandfly fever 2/6/2014 41
  42. 42. Lice and VBDs – Typhus Fever  Agent: Rickettsia prowazeckii Vector: body lice (Pediculus humanus corporis)  Other louse-borne diseases  Trench fever – Bartonella quintana (bacterium)  Relapsing fever – Borrellia recurrentensis 2/6/2014 42
  43. 43. Fleas and VBDs - Plague  Plague: Pasteurella (now Yersinia) pestis  Historically, a cause of major epidemics and pandemics  Now readily controllable with antibiotics  Concern as a bioterrorism agent 2/6/2014 43
  44. 44. Ticks and VBDs  Rocky Mountain Spotted Fever – Rickettsia rickettsi –  Lyme disease – spirochete bacterium – Borrelia burgdorferi  Ehrlichiosis - Ehrlichia chaffeensis – a bacterium  Q fever: Coxiella burnetti – ricketsia - zoonotic  Tularemia – Francisella tularensis – zoonotic  CCHF – reports from Gujarat 2/6/2014 44
  45. 45. VBDs  Why should we be concerned ? 2/6/2014 45
  46. 46. GLOBAL SITUATION  These diseases represent 17% of the global disease burden  300 million malaria cases (WHO, 2009a),  50–100 million dengue cases (WHO, 2009b),  120 million filariasis cases (WHO, 2000). 2/6/2014 46
  47. 47. 2/6/2014 47
  48. 48. 2/6/2014 48
  49. 49. Filariasis 2/6/2014 49
  50. 50. Dengue 2/6/2014 50
  51. 51. Malaria 2/6/2014 51
  52. 52. Malaria  Every year, 500 million people become severely ill with malaria  causes 30% of Low birth weight in newborns Globally.  >1 million people die of malaria every year. One child dies from it every 30 seconds  40% of the world’s population is at risk of malaria. Most cases and deaths occur in SSA.  Malaria is the 9th leading cause of death in LICs and MICs   11% of childhood deaths worldwide attributable to malaria SSA children account for 82% of malaria deaths worldwide
  53. 53. 2/6/2014 53
  54. 54. African Trypanosomiasis  Related trypanosome responsible for African Sleeping Sickness  T. gambiense T. rhodesiense  Tsetse fly vector  Larger than T. cruzi 2/6/2014 54
  55. 55. Yellow fever endemic areas 2/6/2014 55
  56. 56. 2000 2/6/2014 56
  57. 57. 2001 2/6/2014 57
  58. 58. 2002 2/6/2014 58
  59. 59. 2005 2/6/2014 59
  60. 60. 2007 2/6/2014 60
  61. 61. West Nile Virus - The most widespread of the JE serocomplex flaviviruses 2/6/2014 61
  62. 62. DENGUE AFFECTED AREA
  63. 63. 2/6/2014 64
  64. 64. Vector-borne Disease -Incidence Worldwide Disease Estimated annual cases  Malaria 300,000,000  Filariasis 120,000,000  Dengue/DHF 20,000,000  Onchocerciasis 18,000,000  Chagas disease 16-18,000,000  Leishmaniasis 12,000,000  Sleeping sickness 300-400,000  Yellow fever 200,000  Lyme disease 100,000s  West Nile Virus 100,000s  Japanese encephalitis 50,000  Tick-borne encephalitis 10,000  Ehrlichiosis 10,000s  Plague 3,000  Rift Valley 1,000s  Venezuelan Equine encephalitis 1000s  Typhus – louse-borne 100s 2/6/2014 Trends ↑ ↓ ↑ ↓ ↓ ↑ ↑ ↔ ↑ ↑ ↑ ↑ ↑ ↔ ↑ ↔ ↔ Data from Dr. Norman Gratz, WHO 65
  65. 65. Why worry about vector-borne diseases?  Negative impact on commerce, travel, & economies (e.g., Rift Valley fever, yellow fever)  Explosive debilitating outbreaks (e.g., yellow fever)  Poorest are worst affected – min access to health care  Preventable cause of human illness & death 2/6/2014 66
  66. 66. 2/6/2014 67 Charrel et al. 2007. N Engl J Med 356;8
  67. 67. VBDs  Neglected tropical diseases -Lymphatic filariasis (LF), soil transmitted helminthiasis (STH), visceral leishamaniasis (VL), trachoma, yaws, schistosomiasis, dengue, rabies, leprosy, leptospirosis, Japanese encephalitis (JE) and Chikungunya  Bioterrorism – Y. pestis  Emerging diseases – Hemorrhagic fevers, Dengue  Re-emerging diseases – Malaria 2/6/2014 68
  68. 68. Selected emerging and re-emerging infectious diseases, 1996-2004 Heymann DL. Emerging and re-emerging infections. In Oxford Textbook of Public Health, 5th ed, 2009, p1266. 2/6/2014 69
  69. 69. Malaria, yellow fever, dengue, West Nile virus, chikungunya, WHAT’S NEXT? 2/6/2014 70
  70. 70. 2/6/2014 71
  71. 71. Resistance  Vector resistance  Drug resistance of plasmodium 2/6/2014 72
  72. 72. Drug Resistance  Choloroquine  Sulpha- Pyremethamine  Quinine  Mefloquine  Artemesinin 2/6/2014 74
  73. 73. How Env change affects VBDs? Dr. Paul Reiter: “The natural history of mosquito-borne diseases is complex, and the interplay of climate, ecology, vector biology, and many other factors defies simplistic analysis.” Environmental Health Perspectives, Vol. 109, 2001. pp. 141-161. 2/6/2014 75
  74. 74. Human-Driven Ecological Changes that alter Incidence of Mosquito-Borne Diseases  Deforestation  Large-scale water projects  Global climate change  Urbanization  Industrial agriculture practices  Industrial animal husbandry practices  Widespread use of pesticides  Water pollution  Introduction of exotic species  Tendency towards monoculture 2/6/2014 76
  75. 75. The combination of increasing population and resource consumption, along with waste generation, drives the regional environmental change typically indicated by trends in land use and land cover change. Three characteristic processes occur in relation to land use: urbanization, agricultural intensification (including food production and distribution) and alteration of forest habitat which drives disease emergence. 2/6/2014 77
  76. 76. Global Climate Change + 8 - 16 C +5-7 C +3-8 C +4-8 C Interactive map: www.actoncopenhagen.decc.gov.uk 2/6/2014 Source: Met Office Hadley Centre 78
  77. 77. ANTARCTIC OZONE HOLE-2006. courtesy NASA. 2/6/2014 79
  78. 78. What diseases are the most climate sensitive? Sensitivity High Low 2/6/2014 – – – – – – – – heat stress effects of storms air pollution effects asthma vector-borne diseases water-borne diseases food-borne diseases sexually-transmitted diseases 80
  79. 79. Hypothesis: global warming will increase the incidence of vector-borne infectious diseases RATIONALE  “Bugs” like warmth  Vector-borne diseases don’t occur much in winter, or in the Arctic or Antarctic, or on high mountains. 2/6/2014 81
  80. 80. Environment and Exposure Where might Climate Impact? Direct Exposure Indirect Exposure Anthroponotic Infections Humans Humans Vehicle Humans 2/6/2014 STDs Measles Hepatitis B Vehicle Humans Malaria Dengue Roundworm 82
  81. 81. Environment and Exposure Where might Climate Impact? Direct Exposure Indirect Exposure Zoonotic Infections Animals Animals Vehicle Animals Humans 2/6/2014 Vehicle Animals Anthrax Ebola (?) CJD Humans Lyme Disease Hantaviral Disease Most arboviral diseases 83
  82. 82. increases in global temperatures, + more frequent extreme weather events, + warmer winters and evenings + Other cofactors (biodiversity loss, urbanization) = opportunity for increased distribution, expanded breeding, prolonged mosquito incubation period . 2/6/2014 84
  83. 83. Increased Malaria Risk  The IPCC has noted that the global population at risk from vector-borne malaria will increase by between 220 million and 400 million in the next century  While most of the increase is predicted to occur in Africa, some increased risk is projected in Britain, Australia, India and Portugal 2/6/2014 85
  84. 84. FACTORS CONTRIBUTING TO EMERGENCE OR REEMERGENCE OF INFECTIOUS DISEASES  Resistance of the vectors of vector-borne infectious diseases to pesticides.  Immunosuppression of persons due to medical treatments or new diseases that result in infectious diseases caused by agents not usually pathogenic in healthy hosts.(e.g. leukemia patients) 2/6/2014 86
  85. 85. Insects-Bioterrorism ?? Of the 22 prime candidates, half were arthropod-borne viruses. Lockwood JA. Six-Legged Soldiers: Using Insects as Weapons of War. Oxford University Press, Inc., New York, 2009, pp 400. 2/6/2014 87
  86. 86. International commerce and travel Land use and deforestation Climate change and variability Human behavior and prevention strategies Vector-borne diseases Water storage and irrigation Human population growth Poverty Modified from Sutherst R.W. Clin Micribiol Rev 2004;17:136-73 2/6/2014 88
  87. 87. Changing Epidemiology  Areas affected by Malaria – Env change  P. falciparum proportion  Paradigms – Border, Project, Migrant, Tribal  Epidemics of VBDs - Dengue  Diagnostics- Microscope to RDTs 2/6/2014 89
  88. 88. Changing Epidemiology  Treatment- Chloroquine to ACT  Resistance – reported and rising  Prevention – IRS to LLINs  Vaccine development  Control - Eradication - Control  MDGs  RS & GIS – Surveillance 2/6/2014 90
  89. 89. Thank You 2/6/2014 91

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