Study the different patterns of malaria epidemiology (human & vector)to understand why they are resilient to current control strategies, has three majors components:
Cross sectional survey:
Repeated surveys to assess temporal and spatial changes in the prevalence of P. falciparum infection in a Dynamic Cohort of Children â‰¥ 6 months of age and adults: At the catchment areas of Dangassa, Dioro and Sirakorola, we will estimate the rates of asymptomatic P. falciparum infection based on two Cohort-based surveys each year, one at onset (May/June l) and one at the end of the rainy season (October/November). During the cross sectional, the ICEMR team will work closely with local guide to search for and identify all participants of the study cohorts within each village. The investigation team will work at the community health center for 12 to 14 days. Selected children and adults will be examined clinically to detect symptoms associated with malaria (fever, history of fever, spleen index, and anemia). Approximately 500Âµl of peripheral blood will be dropped from participant by finger prick. Collected blood will be used to assess the presence of parasite by blood smears, the RBC polymorphisms detection (HbS, HbC, HbF, G6PD deficiency, Î±-thalassemia, ABO blood groups), Hb level measurement, and two spots on filter paper for parasite and human DNA extraction to assess genetic diversity, pharmacogenomics and malaria drugs resistance markers.
Passive Case Detection (PCD):
Incidence of uncomplicated and severe malaria in a Dynamic Cohort of Children â‰¥ 6 months of age and adult: At the Health Center for each site, passive case detection (PCD) will be performed all year-long. Study cohort members will be encouraged to attend their local Health Clinic if they are febrile, where they will be examined by study physicians. A rapid diagnostic test (RDT) for P. falciparum malaria will be performed, blood smears will be taken on slides and filter papers for microscopy and parasite genotyping. Treatment of malaria will be provided free of charge for all participants by the local health officer following the MoH guidelines.
Pyrethrum Spray Catches (PSC):
Using ArcGis, we will employ grid sampling at each site, with random selection of 90 houses within grid sectors that overlap the areas from which samples will be collected for human epidemiological studies. Houses within grid sectors will be selected at random, stratified by alternative house-roof types (thatch roof vs. metal roof) and by house compounds. The idea is to guarantee appropriate coverage of different types of rooms and to prevent selection of multiple rooms within single compounds (aggregations of rooms). Collections will be conducted in each catchment according to human epidemiological surveys (at least two weeks earlier) schedule in September-October (end of the transmission season) and March/April (dry season). Mosquito collection will be made every two days (30 rooms per collection day) and three PSC collection per village per survey. Each survey a team of 3-4 entomologists will spend twelve days on each study site to conduct both day (spray-catch) and night catches (HLC). During that stay, all selected houses will be sprayed. Spray operations will be conducted between day times. The number of persons having slept the previous night in the room will be recorded as well as the type of the house based on the roof (thatch, metal or wood/mud). The name of the owner of the room and that of the chief of the family (compound) will be recorded as well. Presence of other species of mosquito and hanging ITNs/LLINs will be recorded. The very same selected houses will be sprayed at each time point. The number of Anopheles gambiae and Anopheles funestus will be counted per house and recorded according to their abdominal stage phenotype (i.e., fed, unfed, half-gravid and gravid). Individual specimens will be dissected into abdomen and head/thorax and conserved in microtubes into 80% ethanol or silica gel. The microtubes will be labeled to indicate collection site, the room ID number and the collection date. Both tubes for a given mosquito will have the exact same label. Microtubes will be grouped according to head/thorax and abdomen. The group will also be labeled to indicate the collection date and site, the species, the number of samples, the tissue type (head/thorax or abdomen). They will be held at room temperature for 24 hours and then stored at -70 or -80ÂºC until needed. The spraying itself will be conducted using bomb insecticide available on local markets. They usually contain pyrethroids and some type of organophosphate.
Human Landing Catches (HLC)
In each catchments area, three HLC will be performed (one every two days). In each village 6 collection sites will be identified to reflect the ecology of the villages. Collection will be done inside and outside human dwelling from 6 PM to 6 AM. The HLC will be done during PSC session in each village. in each collection site. These mosquitoes will be morphologicaly identified and dissected on the field for age grading. The assessment of blood sources and sporozoitic rate will be performed in lab4.2.8 CDC light traps (only in Koula) CDC light traps will be used to sample the active portion of the mosquito population. The sentinel collection site will be selected as described in the HLC section. A CDC light trap will be set up at each collection point at 5-6 feet from the ground in each sampling site. Each trap will be set with a dry ice supplement (quantity of 2.0 to 2.5 lbs). The dry ice will be hung directly above, or adjacent to and slightly below, the lid of the CDC trap to draw mosquitoes as close as possible to the collection fan. Trap will be set out from at least one hour prior to dusk until one hour after dawn. In the morning mosquitoes will be identified to species and a subsample will be dissected to determine the parous rates. The remaining tissue will be used to determine the species ID by molecular means and the P. falciparum infection rates by ELISA. Larval and/or adult collection for insecticide resistance test One resistance test will be done per year in each site. Larvae collected on the field and reared at the insectary in the lab will be used. However, in case there is no sufficient larvae, F1 adult obtained from wild adult mosquitoes collected on the study sites will be tested.
|AIM #1 : Assess temporal and spatial changes in the prevalence of P. falciparum infection in a dynamic Cohort in relation to ongoing malaria control interventions.||Hypothesis #1: Wide deployment and continuous control interventions may reduce the intensity of malaria transmission (asymptomatic P. falciparum infection, gametocyte carriage and malaria related anemia).|
|AIM #2: Determine the incidence of uncomplicated and severe malaria in a dynamic cohort in relation to ongoing malaria control interventions.||Hypothesis #2: Control interventions targeting specific age groups may change the age structure of malaria epidemiology (age shift, rebound effect)|
|AIM #3a: Determine seasonal changes in malaria transmission pattern in vector population in relation to ongoing malaria control interventions.||Hypothesis #3a: High coverage and usage of vector control intervention (LLINs & IRS) may reduce entomological inoculation rate over time.|
|AIM #3b: Monitoring insecticide resistance to determine the prevalence of insecticide resistance and its effect on malaria transmission using WHO standard tubes test and molecular assays.||Hypothesis #3b: Long-term usage of indoor vector control intervention (LLINs & IRS) may change vector biting and resting behavior and susceptibility to insecticides|