Defining malaria transmission dynamics in the Gambia
The objectives of this proposed research program are both to understand the dynamics of malaria transmission in a context of high coverage of standard control interventions, and to provide the tools to identify the residual reservoir of infection.
The specific objectives are:
- To evaluate the impact of Mass Drug Administration (MDA) on clinical malaria
- To determine the impact of two single annual MDA rounds on P. falciparum infection
- To determine the seasonal dynamics of asymptomatic infections, gametocytaemia and subpatent infections before and after MDA
This proposed research program to be carried out in The Gambia aims at providing sub-Saharan African National Malaria Control Programs with the necessary knowledge and tools to move farther towards malaria elimination. The Gambia is the ideal place to carry out the proposed research program because (i) The country has been extremely successful in reducing the malaria burden and aims at reducing it further, and (ii) The MRC laboratories have the required expertise, the advanced technological platform and the necessary international collaborations to achieve the program's objectives. The combination of these two factors is unique in West Africa and offers a golden opportunity to carry out a research programme that can have a profound influence on the way elimination efforts will be implemented in sub-Saharan Africa.
Activities are divided into two parallel and complementary sections: one section aims at understanding the dynamics of malaria transmission and the reasons why this can substantially differ within few kilometres; the other section will aim at improving diagnostic tests able to identify malaria-infected but otherwise healthy people (malaria carriers).
For the former, the populations of 12 villages will be intensively followed up for 3 transmission seasons to understand who the malaria carriers are and how the infection spreads across the populations. Information on the vector population, including the presence of insecticide resistance, and on the human behaviour will be collected to partly explain the likely differences between the study villages.
At the end of the study, we will have a better understanding on how the malaria parasites spread and what are the important determinants that maintain transmission from one year to the other, despite the high coverage of preventive and curative measures.
Concerning diagnostic tests, the currently available tests that can be used in the field cannot detect a proportion of infected people that contribute to maintaining transmission. Two approaches will be tried, one aiming at developing an easy-to-use molecular test that can detect most infected individuals, and the other looking at "markers" of infection by detecting parasite's or host's proteins that can be found only in infected individuals. The latter could provide the knowledge necessary to develop a more sensitive test.
- Drug & regimen: Two yearly rounds conducted at the start of the transmission seasons in June 2014 and May 2015 with dihydroartemisinin-piperaquine (weight-based dosage) through DOT mode of delivery
- Concomitant interventions: LLIN (coverage 73-81%), sensitization meetings, annual IRS in moderate transmission areas (eastern region of the country)
- Inclusion criteria: All residents over 6 months old in 2013 and individuals willing to remain in the village for at least 6 months
- Exclusion criteria: Pregnant women (but ensured they received sulfadoxine-pyrimethamine for IPTp), infants below 5 kg, individuals above 75 years old (*But all were included in the surveys)
- Outcome measures:
- (Primary outcome) P. falciparum infection Incidence and prevalence determined by PCR
- (Secondary outcomes) Clinical Malaria incidence and prevalence (passive detection), adverse events, gametocytes determined by QT NASBA and microscopy
- Time of follow-up: 6 months
Allocation: Non- Randomized
Intervention model: Single group assignment
Masking: None (open label)
Primary purpose: Treatment