Estimating the extrinsic incubation period of malaria using a mechanistic model of sporogony

During sporogony, malaria-causing parasites infect a mosquito, reproduce and migrate to the mosquito salivary glands where they can be transmitted the next time blood feeding occurs. The time required for sporogony, known as the extrinsic incubation period (EIP), is an important determinant of malar...

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Bibliographic Details
Published in:PLoS computational biology 2021-02, Vol.17 (2), p.e1008658
Main Authors: Stopard, Isaac J, Churcher, Thomas S, Lambert, Ben
Format: Article
Language:English
Subjects:
Algorithms
Animals
Anopheles
Biology and Life Sciences
Blood
Blood cells
Computer Simulation
Culicidae
Disease transmission
Erythrocytes
Gametocytes
Humans
Incubation
Infections
Infectious Disease Incubation Period
Laboratories
Larvae
Life expectancy
Life span
Malaria
Malaria, Falciparum - transmission
Medicine and Health Sciences
Membranes
Models, Theoretical
Mosquito Vectors - parasitology
Mosquitoes
Oocysts
Parasites
Plasmodium falciparum
Population
Prevalence
Red blood cells
Salivary Glands - parasitology
Sporogony
Sporozoites
Sporozoites - metabolism
Temperature
Time Factors
Vector-borne diseases
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Summary:During sporogony, malaria-causing parasites infect a mosquito, reproduce and migrate to the mosquito salivary glands where they can be transmitted the next time blood feeding occurs. The time required for sporogony, known as the extrinsic incubation period (EIP), is an important determinant of malaria transmission intensity. The EIP is typically estimated as the time for a given percentile, x, of infected mosquitoes to develop salivary gland sporozoites (the infectious parasite life stage), which is denoted by EIPx. Many mechanisms, however, affect the observed sporozoite prevalence including the human-to-mosquito transmission probability and possibly differences in mosquito mortality according to infection status. To account for these various mechanisms, we present a mechanistic mathematical model, which explicitly models key processes at the parasite, mosquito and observational scales. Fitting this model to experimental data, we find greater variation in the EIP than previously thought: we estimated the range between EIP10 and EIP90 (at 27°C) as 4.5 days compared to 0.9 days using existing statistical methods. This pattern holds over the range of study temperatures included in the dataset. Increasing temperature from 21°C to 34°C decreased the EIP50 from 16.1 to 8.8 days. Our work highlights the importance of mechanistic modelling of sporogony to (1) improve estimates of malaria transmission under different environmental conditions or disease control programs and (2) evaluate novel interventions that target the mosquito life stages of the parasite.
ISSN:1553-7358
1553-734X
1553-7358
DOI:10.1371/JOURNAL.PCBI.1008658