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Arvind Kushwaha

This document discusses vector-borne diseases (VBDs) and their history, epidemiology, and impact. It notes that VBDs represent 17% of the global disease burden and cause millions of cases and deaths annually from diseases like malaria, dengue, and filariasis. The document covers the basic concepts of VBD transmission cycles and how environmental factors can influence disease spread. It outlines the roles of mosquitoes, flies, lice, fleas, and ticks as disease vectors. The history of medical entomology and associations between vectors and major diseases are also summarized.

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"India lives in its villages" 2/6/2014 1
 Why we took more than 60 years to realize the value of health of rural India (NRHM ) 2/6/2014 2
EPIDEMIOLOGY OF VBDs  Enemy’ size -------------------- potential of its threat 2/6/2014 3
2/6/2014 4
2/6/2014 5
YELLOW FEVER 2/6/2014 6
570 million years 200,000 years 1,170,000 species 2/6/2014 7
SCHEME OF PRESENTATION  HISTORY  BASIC CONCEPTS IN VBDs  WHY VBDs SHOULD CONCERN US  CLIMATE CHANGE & VBDs  CHALLENGES IN VBDS  SUMMARY 2/6/2014 8
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
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
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
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
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
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
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
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
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
SCHEME OF PRESENTATION  HISTORY  BASIC CONCEPTS IN VBDs  WHY VBDs SHOULD CONCERN US  CLIMATE CHANGE & VBDs  CHALLENGES IN VBDS  SUMMARY 2/6/2014 18
BASIC CONCEPTS  HIGH TRANSMISSIBILITY.  HOST ANIMALS -----VECTOR-----HUMANS  VECTORS DON’T BECOME “ILL” 2/6/2014 19
Phylum Arthropoda :• Bilaterally symmetrical • Jointed legs • Dorsal heart – open circulatory system • CNS (organized central nervous system) • Striated muscle 2/6/2014 20
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
Insect Characteristics THREE distinct body regions: - Head (feeding, sensory, CNS) - Thorax (locomotion, respiration) - Abdomen (feeding, reproduction) 2/6/2014 22
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
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
INCRIMINATING A VECTOR KOCH'S POSTULATES  ASSOCIATION  SPECIFIC CONNECTION  TRANSMISSION  BIOLOGICAL GRADIENT 2/6/2014 25
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
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
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
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
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
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
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
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
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
2 TYPES OF VERTICAL TRANSMISSION: EGGS •Transstadial transmission LARVAE •Transovarial transmission ADULT •Venereal transmission 2/6/2014 35
MODES OF TRANSMISSION HORIZONTAL TRANSMISSION: Passage of parasites/pathogens between vector and host. VECTOR 2/6/2014 HOST 36
“Bridging” mosquito species in yellow fever another infected mosquito species transmits pathogen now to humans “Bridging” PRIMARY VECTOR 2/6/2014 37
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
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
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
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
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
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
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
VBDs  Why should we be concerned ? 2/6/2014 45
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
2/6/2014 47
2/6/2014 48
Filariasis 2/6/2014 49
Dengue 2/6/2014 50
Malaria 2/6/2014 51
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
2/6/2014 53
African Trypanosomiasis  Related trypanosome responsible for African Sleeping Sickness  T. gambiense T. rhodesiense  Tsetse fly vector  Larger than T. cruzi 2/6/2014 54
Yellow fever endemic areas 2/6/2014 55
2000 2/6/2014 56
2001 2/6/2014 57
2002 2/6/2014 58
2005 2/6/2014 59
2007 2/6/2014 60
West Nile Virus - The most widespread of the JE serocomplex flaviviruses 2/6/2014 61
vector borne diseases-ASK
DENGUE AFFECTED AREA
2/6/2014 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
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
2/6/2014 67 Charrel et al. 2007. N Engl J Med 356;8
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
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
Malaria, yellow fever, dengue, West Nile virus, chikungunya, WHAT’S NEXT? 2/6/2014 70
2/6/2014 71
Resistance  Vector resistance  Drug resistance of plasmodium 2/6/2014 72
vector borne diseases-ASK
Drug Resistance  Choloroquine  Sulpha- Pyremethamine  Quinine  Mefloquine  Artemesinin 2/6/2014 74
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
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
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
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
ANTARCTIC OZONE HOLE-2006. courtesy NASA. 2/6/2014 79
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
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
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
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
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
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
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
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
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
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
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
Thank You 2/6/2014 91

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vector borne diseases-ASK

  • 1. "India lives in its villages" 2/6/2014 1
  • 2.  Why we took more than 60 years to realize the value of health of rural India (NRHM ) 2/6/2014 2
  • 3. EPIDEMIOLOGY OF VBDs  Enemy’ size -------------------- potential of its threat 2/6/2014 3
  • 7. 570 million years 200,000 years 1,170,000 species 2/6/2014 7
  • 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. BASIC CONCEPTS  HIGH TRANSMISSIBILITY.  HOST ANIMALS -----VECTOR-----HUMANS  VECTORS DON’T BECOME “ILL” 2/6/2014 19
  • 20. Phylum Arthropoda :• Bilaterally symmetrical • Jointed legs • Dorsal heart – open circulatory system • CNS (organized central nervous system) • Striated muscle 2/6/2014 20
  • 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. Insect Characteristics THREE distinct body regions: - Head (feeding, sensory, CNS) - Thorax (locomotion, respiration) - Abdomen (feeding, reproduction) 2/6/2014 22
  • 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. 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. INCRIMINATING A VECTOR KOCH'S POSTULATES  ASSOCIATION  SPECIFIC CONNECTION  TRANSMISSION  BIOLOGICAL GRADIENT 2/6/2014 25
  • 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. 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. 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. 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. 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. 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. 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. 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. 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. 2 TYPES OF VERTICAL TRANSMISSION: EGGS •Transstadial transmission LARVAE •Transovarial transmission ADULT •Venereal transmission 2/6/2014 35
  • 36. MODES OF TRANSMISSION HORIZONTAL TRANSMISSION: Passage of parasites/pathogens between vector and host. VECTOR 2/6/2014 HOST 36
  • 37. “Bridging” mosquito species in yellow fever another infected mosquito species transmits pathogen now to humans “Bridging” PRIMARY VECTOR 2/6/2014 37
  • 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. 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. 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. 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. 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. 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. 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. VBDs  Why should we be concerned ? 2/6/2014 45
  • 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
  • 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
  • 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. Yellow fever endemic areas 2/6/2014 55
  • 61. West Nile Virus - The most widespread of the JE serocomplex flaviviruses 2/6/2014 61
  • 65. 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
  • 66. 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
  • 67. 2/6/2014 67 Charrel et al. 2007. N Engl J Med 356;8
  • 68. 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
  • 69. 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
  • 70. Malaria, yellow fever, dengue, West Nile virus, chikungunya, WHAT’S NEXT? 2/6/2014 70
  • 72. Resistance  Vector resistance  Drug resistance of plasmodium 2/6/2014 72
  • 74. Drug Resistance  Choloroquine  Sulpha- Pyremethamine  Quinine  Mefloquine  Artemesinin 2/6/2014 74
  • 75. 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
  • 76. 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
  • 77. 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
  • 78. 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
  • 79. ANTARCTIC OZONE HOLE-2006. courtesy NASA. 2/6/2014 79
  • 80. 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
  • 81. 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
  • 82. 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
  • 83. 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
  • 84. 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
  • 85. 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
  • 86. 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
  • 87. 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
  • 88. 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
  • 89. 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
  • 90. 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

Editor's Notes

  • #4: Can you see something on the screen. Enemy’ size (Vector & microbes they carry) may not determine the potential of its threat always.
  • #5: Vectors shouldn’t be thought of as mere dumb vessels or flying hypodermicneedles. It is helpful to think of them as tiny, well-programmed robots.
  • #6: The Black Death, decimator of Europe, killer of tens of millions worldwide is the work of a tiny flea vectoring the bacilli that cause bubonic plague from rats to people.
  • #8: The arthropods are by far the most successful phylum of animals, both in diversity of distribution and in numbers of species and individuals. They have adapted successfully to life in water, on land and in the air.
  • #13: Malaria parasites in human blood - Laveran, 1894- Ross, 1897Transmission of bird malaria by Culex mosquitoes - Ross, 1898Complete development of human malaria parasite in mosquitoes - Grassi, 1898Transmission of human malarial parasite by mosquitoes - Sambon and Low, 1899Only Anopheles mosquitoes transmit human malarial parasites - Watson and Christophers, 1899
  • #14: History of VBDs continues to evolve not only due to new agents being discovered but also due to Changing epidemiology of VBDs and adaptation and evolution of the vector due to ecological pressures.
  • #15: Malaria has shaped the course of history for millennia. It has always been part of the ups and downs of nations; of wars and of upheavals. Kings, popes, and military leaders were struck down in their prime by malaria.Alexander the Great, conqueror of many nations, was vanquished by the bite of a tiny mosquito bearing malaria parasites in the marshes of what is now called Iraq.  
  • #17: These aresome statistics from different wars highlighting the contribution made by VBDs to the burden of Non- Battle casualties. The Malaria and typhus fevers being major problems of the soldiers. The history of many campaigns would have been different but for malaria.
  • #19: Now we shall see some basic concepts related to VBDs.
  • #20: The defining characteristic of a vector-borne infection is its high transmissibility.Vectors help pathogens bridge the gap from a diverse array of host animals (mice, rats, monkeys, birds, prairie dogs, pigs, etc.) to humans.Vectors generally don’t become “ill” from carrying their various viral, protozoan and nematode infections. They might accrue some damage to their tissues, but in some cases this “damage” actually makes them more likely to transmit and infect. A mosquito with problems in its feeding apparatus will need to take additional bites to complete a blood meal. A flea with a gut clogged with plague bacteria will regurgitate more.
  • #21: Most vectors are arthropods which have the characteristics as given on slide.
  • #23: Head is a multifunctional unit in insects responsible for feeding, sensory inputs and nervous system.
  • #26: ASSOCIATION Demonstrate feeding or other effective contact with host.2. SPECIFIC CONNECTION A convincing biological association in time and/or space of suspected arthropod and host with occurrence of clinical or subclinical infection of host.3. TRANSMISSION Ability to transfer infectious agent under controlled conditions.4. BIOLOGICAL GRADIENT Low and high populations of suspect vector results in low and high cases in susceptible hosts, respectively.
  • #27: When can an Arthropod function as a vector.
  • #28: Blood meals provide an arthropod with nutrients necessary for the metabolism, metamorphosis, and reproduction
  • #29: The reproductive cycle of an arthropod is called its gonotrophic cycle.
  • #33: Propagative transmission-organism undergoes a change in its numbers, i.e. amplification only in the body of the vector. (e.g. viruses, YF, WNV, EEE, etc.)Cyclo-developmental transmission-organism undergoes cyclical change but does not multiply. (e.g. Wuchereriabancrofti-Bancroftianfilariasis)Cyclo-propagative transmission-organism undergoes a cyclical change and multiplies.(e.g. malaria, Chagas)
  • #36: Transstadial transmission:sequential passage of parasites from one life stage to next when it occurs from adult to egg called: transovarial transmissionalso termed transgenerationalvenereal transmission: occurs as a result of passage of parasites between male and female vectors. RARE
  • #46: In an era of NCDs like CHD, DM, HTN which our colleagues in the clinics so fondly talk of, why should we in the field of Public Health be harping on VBDs. Malaria has reduced, Typhus has come down, so many infections can now be prevented by a shot of vaccine. There are a number of reasons to explain our concern.
  • #47: The toll from other vector-borne diseases like trypanosomiasis, leishmaniasis, Japanese encephalitis, onchocerciasis and yellow fever add more millions of cases each year.
  • #49: If only mortality due to VBDs was not enough, these VBDs can put humans through lifelong suffering.
  • #50: Filariasis is one such disease. Can you name another dreaded disease though not a VBD ------Leprosy.
  • #51: The Dengue virus continues to spread its area of influence relentlessly, thanx to our indiscriminate urbanisation and use of disposable containers which we tend to throw around so carelessly.
  • #52: Malaria was, is and will continue to be with us for ages to come. Malaria has reminded us of our limitations in our abilities to combat this tiny but very powerful adversary in hsitory of Public health.
  • #63: The National Vector Borne Disease Control programme (NVBDCP) is providing 100% centralassistance to the seven North Eastern states for malaria control activities including provision ofmanpower, bed nets and spray wages. The Enhanced Malaria Control Project (EMCP) with WorldBank assistance was implemented during 1997-2005 in 100 districts of eight high malaria incidencestates. The World Bank is assisting the programme again through the National Vector BorneDisease Control Project (2008-2013) which was launched in September 2008. The IntensifiedMalaria Control Programme (IMCP) funded by Global Fund to Fight AIDS, Tuberculosis and Malaria(GFATM) is in operation since 2005 in 106 districts of 10 states. These projects provide special inputs in these areas in the form of Rapid Diagnostic Tests (RDTs), Artesunate CombinationTherapy (ACT), Insecticde Treated Bednets (ITNs) and Health Systems Strengthening (HSS).
  • #73: Insecticide resistance has been a problem in all insect groups that serve as vectors of emerging diseases. Although mechanisms by which insecticides become less effective are similar across all vector taxa, each resistance problem is potentially unique and may involve a complex pattern of resistance foci. The main defense against resistance is close surveillance of the susceptibility of vector populations.
  • #75: Ever since the discovery of the first case of chloroquine resistance along the Thai-Combodian borderin the late 1950s, Southeast Asia has played an important role as a focus for the development of drugresistance in Plasmodium falciparum. Molecular markers for antimalarial resistance have been identified, including pfmdr-1 and pfcrt polymorphisms associated with chloroquine resistance and dhfr and dhps polymorphisms associated with SP resistance. The dihydrofolatereductaseinhibitors include proguanil, chloroproguanil, pyrimethamine and trimethoprime and sulfa drugs like dapsone, sulfalene, sulfamethoxazole and sulfadoxine. In India chloroquine resistance was first detected in 1973 in Karbi-Anglong district in Assam19 and in 1974 in Nowgong district of Assam. Gradually it has spread towards the west and south, covering almost the entire country. Resistance to SP was first described from theThai-Cambodian border in 1960s. Resistance in P. falciparum to SP combinationwas first detected in Delhi in 1987. Mefloquine resistance was first observed in late 1980snear the Thai-Cambodian border It is frequent in some parts of Southeast Asia. Resistance in P. falciparum to mefloquine in India was detected in Surat district in Gujarat state. .
  • #79: This slide shows the change in temp all over the world. Different lines represent isotherms.
  • #86: IPCC, 2007: Climate Change 2007: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.
  • #88: Stockholm International Peace ResearchInstitute (SIPRI) published a meticulous analysis of themost likely pathogens to be developed as biologicalweapons (Geissler, A New Generation of BiologicalWeapons) [15].