Identifying children with excess malaria episodes after adjusting for variation in exposure: identification from a...

Area of Science:

• Epidemiology
• Infectious Disease Research
• Genetics

Background:

• Clinical malaria episodes in children are over-dispersed, with some experiencing more than expected by chance.
• Micro-epidemiological variations in Plasmodium falciparum exposure are evident in endemic areas.

Purpose of the Study:

• To identify children with excess malaria episodes after controlling for individual malaria exposure levels.

Main Methods:

• A zero-inflated negative binomial model was used to analyze malaria surveillance data from 2,463 children.
• Covariates included age, weighted local infection prevalence (exposure index), and calendar time.
• 100 simulations were run to establish a baseline for expected malaria episodes.

Main Results:

• 212 children (8.6%) were identified with "excess malaria" (EM) exceeding the 95th percentile of simulations.
• The EM group exhibited higher parasite densities during asymptomatic infection and clinical malaria.
• Children with excess malaria were less likely to possess the haemoglobin AS genotype.

Conclusions:

• The zero-inflated negative binomial model best described clinical malaria distribution, considering age, exposure, and time.
• A subset of children experiences excess malaria episodes beyond predictions, indicating unmeasured factors.
• An epidemiological framework is needed to investigate the causes of excess malaria in identified children.