Basics of Malaria Transmission.pptx

7/27/2019 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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Dynamics of Pre Imago stages

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()

= _ [( + + ) ]

()

=

,

()

=

.


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Basics of Malaria Transmission.pptx