Slide 1
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"India lives in its villages"
Why we took more than 60 years to realize the value of health of
rural India (NRHM )
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EPIDEMIOLOGY OF VBDs
Enemy size -------------------- potential of its threat
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Can you see something on the screen. Enemy size (Vector &
microbes they carry) may not determine the potential of its threat
always.
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Vectors shouldnt be thought of as mere dumb vessels or flying
hypodermicneedles. It is helpful to think of them as tiny,
well-programmed robots.
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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.
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YELLOW FEVER
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570 million years
200,000 years
1,170,000 species
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.
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SCHEME OF PRESENTATION
HISTORY
BASIC CONCEPTS IN VBDs
WHY VBDs SHOULD CONCERN US
CLIMATE CHANGE & VBDs
CHALLENGES IN VBDS
SUMMARY
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HISTORY
WORST SCOURGES OF MANKIND
THREAT TO HUMAN SURVIVAL
KILLED MORE MEN THAN ALL THE WARS
CAHNGED THE COURSE OF HISTORY
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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:1700s - Microscope -
Leeuwenhoek1800s - Infectious Disease - Koch et al.
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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 -
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History of Medical Entomology :Laveran MP in blood1896- 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
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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
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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 1940sTicks and
Lyme disease - Spielman, early 1960s
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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.
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MALARIA
>10000 years ago Malaria in Africa19th Century AD-Malaria
almost all over the globeEarly 20th Century AD- Millions die of
malaria almost all over the worldEarly 1950s -Malaria almost
disappears from North America and from almost all of Europe; deaths
mainly in Africa1960-70s: Malaria strikes back with vengeance
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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.
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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 bookThe Prevention of
Malaria.
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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
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These are some 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.
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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.
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There is little information on what the entomologist did during
WWI, although it is known that they did not supervise the drainage
of mosquito breeding areas in the southern training areas.
Poor living conditions & mobile population of soldiers were
faced with threat of epidemic typhus and malaria.
SCHEME OF PRESENTATION
HISTORY
BASIC CONCEPTS IN VBDs
WHY VBDs SHOULD CONCERN US
CLIMATE CHANGE & VBDs
CHALLENGES IN VBDS
SUMMARY
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Now we shall see some basic concepts related to VBDs.
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BASIC CONCEPTS
HIGH TRANSMISSIBILITY.HOST ANIMALS -----VECTOR-----HUMANSVECTORS
DONT BECOME ILL
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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 dont 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.
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Phylum Arthropoda :-
Bilaterally symmetrical
Jointed legs
Dorsal heart open circulatory system
CNS (organized central nervous system)
Striated muscle
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Most vectors are arthropods which have the characteristics as
given on slide.
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Phylum Arthropoda
Class Crustacea - lobsters, crabs, etc.Class Chelicerata -
spiders, mites, ticks, scorpions, etc.Class Diplopoda - millipedes
Class Chilopoda - centipedesClass Insecta - beetles, flies, moths,
mosquitoe.
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Insect Characteristics
THREE distinct body regions: - Head (feeding, sensory, CNS) -
Thorax (locomotion, respiration) - Abdomen (feeding,
reproduction)
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Head is a multifunctional unit in insects responsible for
feeding, sensory inputs and nervous system.
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Arthropods & Health
Direct Causes of Disease or DistressVectors or Hosts of
Pathogenic OrganismsNatural Enemies of other medically harmful
insects
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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
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KOCH'S POSTULATES
ASSOCIATION
SPECIFIC CONNECTION
TRANSMISSION
BIOLOGICAL GRADIENT
INCRIMINATING A VECTOR
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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.
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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.
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When can an Arthropod function as a vector.
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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
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Blood meals provide an arthropod with nutrients necessary for
the metabolism, metamorphosis, and reproduction
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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
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The reproductive cycle of an arthropod is called its gonotrophic
cycle.
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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)
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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
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Viremia
Viremia
Extrinsic
incubation
period
Days
0
5
8
12
16
20
24
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Human #1
Human #2
Illness
Mosquito feeds /
acquires virus
Mosquito refeeds /
transmits virus
Intrinsicincubationperiod
Illness
ILLUSTRATION EXTRINSIC & INTRINSIC INCUBATION PERIODS
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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)
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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. Wuchereria bancrofti-Bancroftian
filariasis)Cyclo-propagative transmission-organism undergoes a
cyclical change and multiplies. (e.g. malaria, Chagas)
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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
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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
offspringF1 GENERATION
F2 GENERATION
OR
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2 TYPES OF VERTICAL TRANSMISSION:
Transstadial transmission
Transovarial transmission
Venereal transmission
EGGS
LARVAE
ADULT
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Transstadial transmission:sequential passage of parasites from
one life stage to next
when it occurs from adult to egg called: transovarial
transmission also termed transgenerational
venereal transmission: occurs as a result of passage of
parasites between male and female vectors. RARE
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MODES OF TRANSMISSION
HORIZONTAL TRANSMISSION:
Passage of parasites/pathogens between vector and host.
VECTOR
HOST
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Bridging
Bridging mosquito species in yellow fever
another infected mosquito species transmits pathogen now to
humans
PRIMARY VECTOR
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Vectorial Capacity is thus, afunctionof
the vector'sdensityinrelationto itsvertebratehost,
thefrequencywith which ittakesbloodmealson the
hostspecies,thedurationof thelatent periodin the vector, and the
vector'slife expectancy.
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 hostPopulation abundance
of vector & hostsDiurnal feeding habits of vectorPathogen
replication in host Host feeding preferencesVector
longevityPrecipitation flooding & droughtTemperatureProximity
of vectors/reservoirs to human populations
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Mosquitoes and Key VBDs
Responsible for a great VBD burdenMalaria parasiteYellow fever
virusDengue fever/hemorrhagic fever virusOther viral feversWest
Nile, Rift Valley, BunyamweraFiliariasis helminthEncephalitis
virusesWestern Equine, Eastern Equine, St. Louis, etc.
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Flies and VBDs
African sleeping sickness african trypanosome parasite tsetse
fly biteEnteric bacteria diseases houseflies food
contaminationVibrio cholerae (cholera), typhoid fever (Salmonella
typhi), Shigella spp. (bacterial dysentery)Onchoceriasis (river
blindness) helminth black fly biteSandfly Kala azar, oriental sore,
sandfly fever
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Lice and VBDs Typhus Fever
Agent: Rickettsia prowazeckiiVector: body lice (Pediculus
humanus corporis)
Other louse-borne diseasesTrench fever Bartonella quintana
(bacterium)Relapsing fever Borrellia recurrentensis
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Fleas and VBDs - Plague
Plague: Pasteurella (now Yersinia) pestisHistorically, a cause
of major epidemics and pandemicsNow readily controllable with
antibioticsConcern as a bioterrorism agent
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Ticks and VBDs
Rocky Mountain Spotted Fever Rickettsia rickettsi Lyme disease
spirochete bacterium Borrelia burgdorferi Ehrlichiosis - Ehrlichia
chaffeensis a bacteriumQ fever: Coxiella burnetti ricketsia -
zoonoticTularemia Francisella tularensis zoonoticCCHF reports from
Gujarat
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VBDs
Why should we be concerned ?
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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.
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GLOBAL SITUATION
These diseases represent 17% of the global disease burden
300 million malaria cases (WHO, 2009a), 50100 million dengue
cases (WHO, 2009b), 120 million filariasis cases (WHO, 2000).
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The toll from other vector-borne diseases like trypanosomiasis,
leishmaniasis, Japanese encephalitis, onchocerciasis and yellow
fever add more millions of cases each year.
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If only mortality due to VBDs was not enough, these VBDs can put
humans through lifelong suffering.
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Filariasis
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Filariasis is one such disease. Can you name another dreaded
disease though not a VBD ------Leprosy.
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Dengue
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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.
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Malaria
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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.
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Malaria
Every year, 500 million people become severely ill with
malariacauses 30% of Low birth weight in newborns Globally.>1
million people die of malaria every year. One child dies from it
every 30 seconds40% of the worlds population is at risk of malaria.
Most cases and deaths occur in SSA.Malaria is the 9th leading cause
of death in LICs and MICs11% of childhood deaths worldwide
attributable to malariaSSA children account for 82% of malaria
deaths worldwide
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More than one million people die of malaria every year, mostly
infants, young children and pregnant women and most of them in
Africa Approximately, 40% of the worlds population, mostly those
living in the worlds poorest countries, are at risk of malaria.
Every year, more than 500 million people become severely ill with
malaria. Most cases and deaths are in sub-Saharan Africa.
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We read in our UG days about Chikungunya as a disease occuring
somewhere in Africa. We now have this debilitating infection
amongst us deeply entrenched.
India is shaded in green (Asian genotype) as outbreaks from 1963
to 1965 and 1973 were confirmed to have been caused by members of
the Asian clade; however, reports from India during 20052007
indicate this outbreak was caused by the same CHIKV strains
detected during the Indian Ocean outbreaks (Central/East African
genotype). Asterisk indicates a location from which CHIKV was
isolated (courtesy: Powers and Logue 2007).The precise reasons for
the re-emergence of chikungunya in the Indian subcontinent as well
as the other small countries in the southern Indian Ocean are an
enigma. Although, it is well recognized that re-emergence of viral
infections are due to a variety of social, environmental,
behavioural and biological changes, which of these contributed to
the re-emergence of chikungunya virus would be interesting to
unravel. Genetic analysis of chiungunya viruses have revealed that
two distinct lineages were delineated,[12] one containing all
isolates from western Africa and the second comprising all southern
and East African strains, as well as isolates from Asia.
Phylogenetic trees corroborated historical evidence that the virus
originated in Africa and subsequently was introduced into Asia
African Trypanosomiasis
Related trypanosome responsible for African Sleeping SicknessT.
gambiense T. rhodesienseTsetse fly vectorLarger than T. cruzi
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Though not yet reported from our country, conditions exist for
this disease to gain ground in future, if we are not vigilant. I
had read an article in which they reported a similar illness
somewhere in Maharashtra, Thank God, it was not proved
conclusively. But this disease is reported in community based
outbreaks during long academic sessions. ( That was on the lighter
side.)
Yellow fever endemic areas
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Another disease we must be alert since all conditions favourable
exist less the agent. Let us keep it off, else it will be a
disaster.
2000
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This is to show how rapidly VBDs can get established and spread
in very short span of time.
2001
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2002
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2005
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2007
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West Nile Virus - The most widespread of the JE serocomplex
flaviviruses
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Id like to start with a few words about the historical
distribution of West Nile.
Even before its expansion into the western hemisphere, in fact
not long after it was first identified in 1937, West Nile virus was
recognized as one of the most widespread of the flaviviruses, with
a distribution that included much of Africa, significant portions
of Europe & Asia, & Australia & parts of southeast Asia
if we include the West Nile virus subtype, Kunjin Virus.
During the 10 years WNV has been active in the Western
hemisphere, its spread has been dramatic, stretching the East to
West breadth of North America, & from central Canada, southward
through portions of the sub-tropics & tropics, to Argentina.
This huge distribution is due to the ability of WNV to survive in a
diversity of ecosystems.
It has been isolated from just over 100 different mosquito
species, 64 in the United States alone, & over 300 bird
species.
Its distribution stretches in both Eastern & Western
hemispheres from the equatorial tropics & subtropics where
transmission can occur year round, to northern climates with short
but very intense transmission seasons punctuated by overwintering
survival of the virus & its vectors.
There are probably few invasive species that are more successful
than WNV in adapting to different ecosystems.
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).
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DENGUE AFFECTED AREA
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Vector-borne Disease -Incidence Worldwide
DiseaseEstimated annual cases TrendsMalaria 300,000,000
Filariasis 120,000,000 Dengue/DHF20,000,000
Onchocerciasis18,000,000 Chagas disease16-18,000,000 Leishmaniasis
12,000,000 Sleeping sickness 300-400,000 Yellow fever 200,000 Lyme
disease100,000s West Nile Virus100,000s Japanese encephalitis50,000
Tick-borne encephalitis10,000Ehrlichiosis10,000s Plague3,000 Rift
Valley 1,000s Venezuelan Equine encephalitis 1000s Typhus
louse-borne100s
Data from Dr. Norman Gratz, WHO
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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
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Charrel et al. 2007. N Engl J Med 356;8
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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
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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
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Emerging Infectious Diseases
Detels - 11 Oct 2010
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Malaria, yellow fever, dengue, West Nile virus,
chikungunya,WHATS NEXT?
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Resistance
Vector resistance
Drug resistance of plasmodium
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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.
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Drug Resistance
CholoroquineSulpha-
PyremethamineQuinineMefloquineArtemesinin
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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 dihydrofolate reductase inhibitors 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. .
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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.
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Human-Driven Ecological Changes that alter Incidence of
Mosquito-Borne Diseases
DeforestationLarge-scale water projectsGlobal climate
changeUrbanizationIndustrial agriculture practicesIndustrial animal
husbandry practicesWidespread use of pesticidesWater
pollutionIntroduction of exotic speciesTendency towards
monoculture
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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.
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Global Climate Change
+ 8 - 16 C
+ 5 - 7 C
+ 3 - 8 C
+ 4 - 8 C
Interactive map: www.actoncopenhagen.decc.gov.uk
Source: Met Office Hadley Centre
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This slide shows the change in temp all over the world.
Different lines represent isotherms.
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ANTARCTIC OZONE HOLE-2006. courtesy NASA.
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What diseases are the mostclimate sensitive?
heat stresseffects of stormsair pollution
effectsasthmavector-borne diseaseswater-borne diseasesfood-borne
diseasessexually-transmitted diseases
High
Low
Sensitivity
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Hypothesis: global warming will increase the incidence of
vector-borne infectious diseases
RATIONALEBugs like warmthVector-borne diseases dont occur much
in winter, or in the Arctic or Antarctic, or on high mountains.
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Anthroponotic Infections
Direct Exposure
Indirect Exposure
Humans
Humans
STDsMeaslesHepatitis B
Vehicle
Humans
Humans
Vehicle
MalariaDengueRoundworm
Environment and ExposureWhere might Climate Impact?
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Zoonotic Infections
Direct Exposure
Indirect Exposure
Vehicle
Vehicle
Animals
Animals
Humans
Lyme DiseaseHantaviral DiseaseMost arboviral diseases
Animals
Animals
Humans
AnthraxEbola (?)CJD
Environment and ExposureWhere might Climate Impact?
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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 .
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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
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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.
85
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)
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Emerging Infectious Diseases
Detels - 11 Oct 2010
86
Insects-Bioterrorism ??
Of the 22 prime candidates, half were
arthropod-borneviruses.
Lockwood JA. Six-Legged Soldiers: Using Insects as Weapons of
War. Oxford University Press, Inc., New York, 2009, pp 400.
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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].
87
Modified from Sutherst R.W. Clin Micribiol Rev
2004;17:136-73
Vector-borne diseases
International commerce and travel
Climate change and variability
Land use and deforestation
Water storage and irrigation
Poverty
Human population growth
Human behavior and prevention strategies
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Changing Epidemiology
Areas affected by Malaria Env changeP. falciparum proportion
Paradigms Border, Project, Migrant, TribalEpidemics of VBDs -
DengueDiagnostics- Microscope to RDTs
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Treatment- Chloroquine to ACTResistance reported and
risingPrevention IRS to LLINsVaccine development Control -
Eradication - Control MDGsRS & GIS Surveillance
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Changing Epidemiology
Thank You
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