Atelier Paludisme 2007 Institut Pasteur de Madagascar 19 Février - 30 Mars Vincent ROBERT Institut de recherche pour le développement (IRD) UR 077 Paludologie afro-tropicale Muséum national d’histoire naturelle (MNHN) USM-504 Biologie fonctionnelle des protozoaires L’hétérogénéité de la transmission doit être prise en compte dans les recherches vaccinales contre le paludisme
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Transmission heterogeneity has consequences on malaria vaccine researches
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Atelier Paludisme 2007
Institut Pasteur de Madagascar
19 Février - 30 Mars
Vincent ROBERTInstitut de recherche pour le développement (IRD) UR 077 Paludologie afro-tropicale
Muséum national d’histoire naturelle (MNHN) USM-504 Biologie fonctionnelle des protozoaires
L’hétérogénéité de la transmission
doit être prise en compte
dans les recherches vaccinales contre le paludisme
Transmissionvectorielle
Transmission des Plasmodium
Anopheles
Aedes
phlébotomes
Bio-écologie
Gamétocytes
Santé publique
Antipaludiques
RésistancePrévention de
l’impaludation
Lutte
antivectorielle
Insecticides
Résistance
Sahara Sahel
Savane Forêt
Madagascar
Villes
Guyane
Transmission des arbovirus
Enseignement
professionnel
supérieur
enfants
Epidémiologie
Evolution
Génétique
Immunologie
VaccinsMoustiquaires
Répulsifs
Plasmodium
animaux
Apicomplexa Piégeage Diagnose Laboratoire
Sporogonie
Mesure de la transmission
Atelier Paludisme
Institut Pasteur de Madagascar
February 29, 2007
Transmission heterogeneity has
consequences on malaria vaccine researches
1 /18
Three modes of transmission :
Transmission • vectorial
• transfusion
• placental
2 /18
MOSQUITO-HUMAN
TRANSMISSION
MOSQUITO
HUMAN
The transmission
HUMAN-MOSQUITO
TRANSMISSSION
? or the two transmissions ?
Vaccines
Inhibition of sporozoite invasion
Inhibition of merozoite invasion
Inhibition of infected red blood cells cyto-adherence
Immunity regulation
Inhibition of sporogonic development
Transmissionblocking vaccines
3 /18
transmission morbidity mortality
the malaria in one slide
Human
uninfected
Human
infectedHuman
sick
Human
dead
natural immunity
- --vector controlprevention of
infection
drug treatment
--- - -
and / or vaccines
4 /18
Transmission and natural immunity are highly linked
If the vaccine would have nothing to deal with the stimulation of natural immunity and only induces new
immunological mechanism of protection (fully different from natural situations), one may speculate :
- the induction of protective immunity by a vaccine is not linked to transmission intensity,
- but the duration of protection might be.
Transmission intensity has important consequences for the
artificial induction of protective immunity by a vaccine
Transmission may act positively, as additional boosters
New infections may act negatively, overwhelming the protective immunity
The development of the vaccine must document transmission intensity,
(except during phases testing safety), as soon as the first phases
testing immunogenicity and efficacy in endemic zones
Infants do not constitute a special issue
5 /18
The measure of The measure of PlasmodiumPlasmodium transmissiontransmission
≠≠ number of inoculation of number of inoculation of PlasmodiumPlasmodium
per person : ordinary, an adultper person : ordinary, an adult
per unit of time : night, month, year, lifeper unit of time : night, month, year, life
Definiti
on
E I R : Entomological Inoculation Rate
EIR = ma x sma = biting rate
s = sporozoite index
Unit : Nb of bites of infected anopheline per human and per unit of time
6 /18
Does EIR measure transmission ?
• Mean on a sample of persons : what about individual variations
for an adult human ?
in a mean environment ?
• Mean on a period time : what about the temporal variations ?
==> specify if transmission is seasonal or permanent,
(duration of season without transmission)
• Measure established from awaked voluntaries
• Give the Nb of bites of infected anophelines
(about double of the Nb of bites that induce blood parasite infection )
EIR is a proxy of malaria transmission
7 /18
8 /18
Incidence of Incidence of P. falciparumP. falciparum simple malaria attackssimple malaria attacks
in relation to age and intensity of transmissionin relation to age and intensity of transmission