Download - Basics of Malaria Transmission.pptx
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Basics of Malaria Transmission
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2/3/2012 2
Malaria Transmission Cycle
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Malaria:Epidemiological Triangle
Environment
Analogy: Development of pathogens in insect vectors
is affected by climatic conditions
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Comparison of
male and female
Anophelines vs.CulicinesCulicine
Anopheline
females
males
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Distribution of vectors of malaria in India
Spatial extension of vectors may be affected; Role ofAn. subpictus and An
Annularis need to be assessed
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MALARIA Parasites
Plasmodium vivax*
Plasmodium falciparum*
Plasmodium ovale Plasmodium malariae
* most common
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Environment
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10 11 12 13
Minimum temp. for
parasite development
Maximum temp.
for mosquito
survival
Optimum
temp.
14 15 16 17 18 19 25 26 27 40 oC
Relative Humidity 40 60 70 80
Relationship of Temp. & RH with Malaria
Parasite and Mosquito Development
Minimum T required for transmission
P vivax: 14.5-16 C Pfalciparum:16-18 C
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Effect of Rise in Temperature on Disease
Vectors
Rate of development (from egg toadults) will be faster
Rate of digestion of blood meal willbe faster.
Frequency of feeding will be faster
Frequency of egg laying willincrease. Density of mosquitoes will increase. Survival affected by RH. Gonotrophic cycle and Longevity for
sporogony reduced at highertemperature Death of mosquitoes at 40C
Gonotrophic cycle, daily survival and man biting rates are
crucial factors for vectorial capacity of vectors
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Climatic Determinants for P. vivax
Development and Transmission
Categories Temperature
range (oC)
Relative
Humidity
(%)
No. of days
to develop
Class I 15-20 >60 and 60 and 60 and
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Average duration of sporogony of human
Plasmodia
Parasite species No of days requiredfor sporogony at
differenttemperatures
200 C 250 C
P falciparum 22-23 12-14
P vivax 16-17 9-10
P malariae 30-35 23-24
P ovale - 15-16
At 16 C , 55 days are required for completion of sporogony
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Coupling of Three Models
Transmission of malaria in Human
Transmission of malaria in Vector population
Modeling the pre imago stages of Vector.
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Classification of Human population
Suceptible (HUS)
Infectious (HUI)
Infected (HUF)
Immune (HUM)
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Transmission of Malaria in host
population
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()
= +
=
[](+) ()
= []+ ,
()
= + VC= Vectoral Capacity
kin= Primary exo erythrocytic schizogony (days)
ker= Erythrocytic Scizoghony (days)
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Susceptible Human
Population
Birth rate
Immunity
Death Rate
VC
Infected HumanPopulationDeath Rate
VC
time-(ker+kin)
InfectiousHuman
Population
Death Rate
Recovery
rate
time-(ker+kin)
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Classification of vector population
Susceptible (VS)
Infectious (VI)
Infected (VF)
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Susceptible Vector
Population
Emergence rate from
Pupa
Death Rate
Mosquitoes which havebitten infectious Human
Infected VectorPopulationDeath Rate
Mosquitoes which have bitten
infectious Human.
Time taken for sporogonic cycl
InfectiousVector
PopulationDeath Rate
Time taken for sporogonic cycle
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Transmission of Malaria in Vector
population
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+
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=
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=
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Dynamics of Pre Imago stages
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()
= _ [( + + ) ]
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=
,
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=
.
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