Plasmodium falciparum; malaria; surveillance; Anopheles gambiae; Africa; near-infrared spectroscopy
Maia Marta F., Kapulu Melissa, Muthui Michelle, Wagah Martin G., Ferguson Heather M., Dowell Floyd E., Baldini Francesco, Ranford-Cartwright Lisa (2019), Detection of Plasmodium falciparum infected Anopheles gambiae using near-infrared spectroscopy, in Malaria Journal
, 18(1), 85-85.
Replication Data for: Near infrared spectra and calibration for detection of malaria infection in Anopheles gambiae (Keele strain)
||Ferreira Maia, Marta; Kapulu, Melissa; Muthui, Michelle; Wagah, Martin; Ferguson, Heather; Dowell, Floyd; Baldini, Francesco
|Persistent Identifier (PID)
Anopheles gambiae (Keele Strain) mosquitoes were infected in the lab with cultured Plasmodium falciparum gametocytes (PfN54) to generate oocyst and sporozoite infected vectors. Controls, uninfected mosquitoes, were generated by feeding mosquitoes on the same blood after gametogenesis had occurred which was triggered by dropping the temperature in the glass feeders to below 30 degrees Celsius. After feeding, mosquitoes were kept for 7 and 14 days to allow parasite development after which each individual mosquito was scanned with near infrared spectroscopy (NIRS) and stored at -20 until processed by qPCR (quantitative polymerase chain reaction) for confirmation of infection and quantification of parasite load. The data shared is composed of all the spectra that were collected (in .spc format for GRAMS IQ software) labeled with a unique identifier which links to the STATA files where the mean number of parasite genomes and age for each individual mosquito are listed. The files used to generate the calibration through partial least square (PLS) regression on GRAMS IQ have also been shared (.tfdx) along with the calibration file (.cal) for uploading on IQ Predict software. We have also shared the prediction outputs of the independent samples that were predicted with the calibrations here developed.
This proposal requests a follow-up grant for an ongoing study (PMPDP3_164444) investigating if near-infrared spectroscopy (NIRS) can detect Plasmodium falciparum infection in mosquitoes. The technology offers an opportunity for the development of a high throughput testing method which would benefit malaria surveillance programs. So far, I have infected mosquitoes in the lab and collected spectra from both uninfected and infected mosquitoes up to oocyst and sporozoite stage. I have determined infection load of each mosquito samples with qPCR and analyzed the spectra data using cross-validations. I can conclude that NIRS can be used to accurately predict Pl. falciparum sporozoite infection in Anopheles gambiae s.s with over 90% sensitivity and specificity independent of infection load. However, the earlier stages of infection in mosquitoes (oocyst stage) did not provide discernable results, cross validations showed that the NIRS spectra between infected and uninfected mosquitoes were not sufficiently different to tell them apart. Although the results for sporozoite-infected mosquitoes are very promising, the method must still be validated using samples from infections closer to what would be found in the wild. I am in Kenya preparing for this stage of the project. I have received all regulatory approvals needed for the study and community engagement in Kilifi has begun; screening for participants will be done following the on-start of the long rains from mid-April to July. The recruited participants will be asked to donate blood to infect mosquitoes in the lab and a few volunteers will be asked to feed the mosquitoes directly on their arms. Mosquitoes will be allowed to develop parasitic infections up to sporozoite stage after which they will be killed and scanned using NIRS. The spectra collected will be used to validate the calibrations previously generated. Screening has not yet begun because prevalence of asymptomatic carriers in the dry season is expected to be very low. To ensure that the project can reach its objectives and recruit its target number of participants for mosquito feeding assays it is advisable to concentrate field activities following the long rains in order not to exhaust the research funds available before reaching the recruitment target. My current fellowship is scheduled to end in July, the additional funds requested in this follow up proposal would allow me enough time to conclude the field work, summarize and disseminate the main findings