Vector Borne Diseases

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Slide 1: 

9/24/2013 1 "India lives in its villages"

Slide 2: 

Why we took more than 60 years to realize the value of health of rural India (NRHM ) 9/24/2013 2

EPIDEMIOLOGY OF VBDs : 

EPIDEMIOLOGY OF VBDs Enemy’ size -------------------- potential of its threat 9/24/2013 3

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9/24/2013 4

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9/24/2013 5

YELLOW FEVER : 

YELLOW FEVER 9/24/2013 6

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9/24/2013 7 570 million years 200,000 years 1,170,000 species

SCHEME OF PRESENTATION : 

SCHEME OF PRESENTATION HISTORY BASIC CONCEPTS IN VBDs WHY VBDs SHOULD CONCERN US CLIMATE CHANGE & VBDs CHALLENGES IN VBDS SUMMARY 9/24/2013 8

HISTORY : 

HISTORY WORST SCOURGES OF MANKIND THREAT TO HUMAN SURVIVAL KILLED MORE MEN THAN ALL THE WARS CAHNGED THE COURSE OF HISTORY 9/24/2013 9

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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. 9/24/2013 10

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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 - 9/24/2013 11

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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 9/24/2013 12

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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 9/24/2013 13

MALARIA : 

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 9/24/2013 14

MALARIA & WARS : 

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. 9/24/2013 15

Cause of Deaths in War : 

Cause of Deaths in War 9/24/2013 16

Military Entomology - World War I : 

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. 9/24/2013 17

SCHEME OF PRESENTATION : 

SCHEME OF PRESENTATION HISTORY BASIC CONCEPTS IN VBDs WHY VBDs SHOULD CONCERN US CLIMATE CHANGE & VBDs CHALLENGES IN VBDS SUMMARY 9/24/2013 18

BASIC CONCEPTS : 

BASIC CONCEPTS HIGH TRANSMISSIBILITY. HOST ANIMALS -----VECTOR-----HUMANS VECTORS DON’T BECOME “ILL” 9/24/2013 19

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Phylum Arthropoda :- Bilaterally symmetrical Jointed legs Dorsal heart – open circulatory system CNS (organized central nervous system) Striated muscle 9/24/2013 20

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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. 9/24/2013 21

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Insect Characteristics THREE distinct body regions: - Head (feeding, sensory, CNS) - Thorax (locomotion, respiration) - Abdomen (feeding, reproduction) 9/24/2013 22

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Arthropods & Health Direct Causes of Disease or Distress Vectors or Hosts of Pathogenic Organisms Natural Enemies of other medically harmful insects 9/24/2013 23

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VECTOR-BORNE DISEASE CONCEPT ARTHROPOD VECTOR VERTEBRATE HOST PATHOGEN Environmental factors (temp, rain) age, abundance, daily activity susceptibilty, accessibility, numbers of hosts, daily activity amplification, maturation, maintenance in nature competence for pathogen 9/24/2013 24

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KOCH'S POSTULATES ASSOCIATION SPECIFIC CONNECTION TRANSMISSION BIOLOGICAL GRADIENT INCRIMINATING A VECTOR 9/24/2013 25

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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. 9/24/2013 26

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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. COMPONENTS OF TRANSMISSION CYCLE 9/24/2013 27

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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 9/24/2013 28

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ARTHROPOD ACQUISITION & DEVELOPMENT OF PATHOGENS PATHOGEN+BLOOD INGESTED (ORAL) PATHOGEN MULTIPLIES OR INACTIVATED (GUT) PATHOGEN PASSAGE THRU GUT WALL OR EPITHELIAL LAYER (GUT) PATHOGEN TRANSPORT BY HEMOLYMPH TO TISSUES OF VECTOR (HEMOLYMPH) TISSUE CONCENTRATION (SALIVARY GLANDS, or REPRODUCTIVE SYSTEM) 9/24/2013 29

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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 9/24/2013 30

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Viremia Viremia Days 0 5 8 12 16 20 24 28 Human #1 Human #2 Mosquito feeds / acquires virus Mosquito refeeds / transmits virus Intrinsic incubation period ILLUSTRATION EXTRINSIC & INTRINSIC INCUBATION PERIODS 9/24/2013 31

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PATHOGEN DEVELOPMENT IN BODY OF VECTOR ARTHROPODS Propagative transmission- (e.g. viruses, YF, WNV, EEE, etc.) Cyclo-developmental (e.g. Wuchereria bancrofti-Bancroftian filariasis) Cyclo-propagative transmission-. (e.g. malaria, Chagas) 9/24/2013 32

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PATHOGEN ACQUISITION BY HOST FROM ARTHROPOD CONTAMINATED MOUTHPARTS ESCAPE THROUGH BODY WALL CONTACT WITH CONTAMINATED BODY SURFACES INFECTIVE FLUIDS FROM GLANDS (e.g. tick coxal glands) BACK PRESSURE DIGESTIVE TRACT INFECTED FECES HOST INGESTS OR CRUSHES INFECTED ARTHROPOD 9/24/2013 33

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MODES OF TRANSMISSION VERTICAL TRANSMISSION: Passage of parasites/pathogens from one life stage to next life stage or generation to generation. EGGS LARVAE ADULT PARENTAL GENERATION offspring F1 GENERATION F2 GENERATION OR 9/24/2013 34

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2 TYPES OF VERTICAL TRANSMISSION: Transstadial transmission Transovarial transmission Venereal transmission EGGS LARVAE ADULT 9/24/2013 35

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MODES OF TRANSMISSION HORIZONTAL TRANSMISSION: Passage of parasites/pathogens between vector and host. VECTOR HOST 9/24/2013 36

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“Bridging” “Bridging” mosquito species in yellow fever another infected mosquito species transmits pathogen now to humans PRIMARY VECTOR 9/24/2013 37

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9/24/2013 38 Vectorial Capacity is  thus, a function of the vector's density in relation to its vertebrate host, the frequency with which it takes blood meals on the host species, the duration of the latent period in the vector, and the vector's life expectancy.

FACTORS THAT STRONGLY AFFECT PATHOGEN TRANSMISSION BY VECTORS : 

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 9/24/2013 39

Mosquitoes and Key VBDs : 

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. 9/24/2013 40

Flies and VBDs : 

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 9/24/2013 41

Lice and VBDs – Typhus Fever : 

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 9/24/2013 42

Fleas and VBDs - Plague : 

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 9/24/2013 43

Ticks and VBDs : 

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 9/24/2013 44

VBDs : 

VBDs Why should we be concerned ? 9/24/2013 45

GLOBAL SITUATION : 

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). 9/24/2013 46

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9/24/2013 47

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9/24/2013 48

Filariasis : 

Filariasis 9/24/2013 49

Dengue : 

Dengue 9/24/2013 50

Malaria : 

Malaria 9/24/2013 51

Malaria : 

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

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9/24/2013 53

African Trypanosomiasis : 

African Trypanosomiasis Related trypanosome responsible for African Sleeping Sickness T. gambiense T. rhodesiense Tsetse fly vector Larger than T. cruzi 9/24/2013 54

Yellow fever endemic areas : 

Yellow fever endemic areas 9/24/2013 55

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2000 9/24/2013 56

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2001 9/24/2013 57

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2002 9/24/2013 58

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2005 9/24/2013 59

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2007 9/24/2013 60

West Nile Virus - The most widespread of the JE serocomplex flaviviruses : 

West Nile Virus - The most widespread of the JE serocomplex flaviviruses 9/24/2013 61

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DENGUE AFFECTED AREA

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9/24/2013 64

Vector-borne Disease -Incidence Worldwide : 

Vector-borne Disease -Incidence Worldwide Disease Estimated annual cases Trends 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 ↔ Data from Dr. Norman Gratz, WHO 9/24/2013 65

Why worry about vector-borne diseases? : 

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 9/24/2013 66

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Charrel et al. 2007. N Engl J Med 356;8 9/24/2013 67

VBDs : 

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 9/24/2013 68

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Heymann DL. Emerging and re-emerging infections. In Oxford Textbook of Public Health, 5th ed, 2009, p1266. Selected emerging and re-emerging infectious diseases, 1996-2004 9/24/2013 69

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Malaria, yellow fever, dengue, West Nile virus, chikungunya, WHAT’S NEXT? 9/24/2013 70

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9/24/2013 71

Resistance : 

Resistance Vector resistance Drug resistance of plasmodium 9/24/2013 72

Drug Resistance : 

Drug Resistance Choloroquine Sulpha- Pyremethamine Quinine Mefloquine Artemesinin 9/24/2013 74

How Env change affects VBDs? : 

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. 9/24/2013 75

Human-Driven Ecological Changes that alter Incidence of Mosquito-Borne Diseases : 

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 9/24/2013 76

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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. 9/24/2013 77

Global Climate Change : 

Global Climate Change Interactive map: www.actoncopenhagen.decc.gov.uk Source: Met Office Hadley Centre 9/24/2013 78

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ANTARCTIC OZONE HOLE-2006. courtesy NASA. 9/24/2013 79

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What diseases are the mostclimate sensitive? heat stress effects of storms air pollution effects asthma vector-borne diseases water-borne diseases food-borne diseases sexually-transmitted diseases High Low Sensitivity 9/24/2013 80

Hypothesis: global warming will increase the incidence of vector-borne infectious diseases : 

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. 9/24/2013 81

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Anthroponotic Infections Environment and Exposure Where might Climate Impact? 9/24/2013 82

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Zoonotic Infections Environment and Exposure Where might Climate Impact? 9/24/2013 83

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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 . 9/24/2013 84

Increased Malaria Risk : 

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 85 9/24/2013

FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES : 

FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE 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) 9/24/2013 86

Insects-Bioterrorism ?? : 

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. 9/24/2013 87

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Modified from Sutherst R.W. Clin Micribiol Rev 2004;17:136-73 International commerce and travel Water storage and irrigation Poverty Human behavior and prevention strategies 9/24/2013 88

Changing Epidemiology : 

Changing Epidemiology Areas affected by Malaria – Env change P. falciparum proportion Paradigms – Border, Project, Migrant, Tribal Epidemics of VBDs - Dengue Diagnostics- Microscope to RDTs 9/24/2013 89

Changing Epidemiology : 

Treatment- Chloroquine to ACT Resistance – reported and rising Prevention – IRS to LLINs Vaccine development Control - Eradication - Control MDGs RS & GIS – Surveillance 9/24/2013 90 Changing Epidemiology

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Thank You 9/24/2013 91

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