This article is the second in a series. Visit the first article to follow along on a day in the life of the entomological collectors who gathered these mosquitoes.
Despite significant achievements in malaria reduction over the past decade, Zambia sees more than 3 million cases annually, with pregnant women and children bearing the heaviest burden.
With funding from the Bill & Melinda Gates Foundation through the Innovative Vector Control Consortium (IVCC), PATH’s Attractive Targeted Sugar Bait (ATSB) project, the Zambia National Elimination Centre (NMEC), and partners are developing and studying innovative vector control tools that accelerate progress towards ending this deadly but preventable disease.
In the last installment in this series, we learned how the team collects data on malaria-carrying mosquitoes from around communities in Kaoma, a town in Zambia's Western Province, and traps them for future study. But what happens to those mosquitoes after the entomological collectors pack the coolers back in their trucks and head home?
That's where the entomology team at the PATH Kaoma Lab step in to continue the work.
"Accurate identification of mosquito species is essential for understanding their role in malaria transmission," says Bongani Muwowo, a PATH entomology lab technician. "The work also gives us insights into mosquito biology, such as their feeding behavior and population dynamics."
The information gathered by the entomology lab team is vital to develop effective vector control strategies to combat malaria transmission in Zambia.
Photo: PATH/Mundia H Masuzyo
Once the entomology collectors finish trapping mosquitoes, they are transported by truck to the PATH Kaoma lab for processing and further study.
Photo: PATH/Mundia H Masuzyo
Upon arrival, the staff sort the coolers by collection site and collection method, then remove the collection cups from the coolers.
Photo: PATH/Mundia H Masuzyo
One by one, the cups are emptied and their contents sorted and identified.
Photo: PATH/Mundia H Masuzyo
The first step is to sort out mosquitoes from any other insects that might have found their way into the trap.
"I use a white background to give me a clear visual," explains Bongani. "It helps me to see the mosquitoes and separate them from the other non-targeted organisms."
Photo: PATH/Mundia H Masuzyo
The mosquitoes are then placed into a petri dish and labeled with all the details about how and where they were caught.
Photo: PATH/Mundia H Masuzyo
The petri dishes are also labeled with a unique QR code that will connect to this petri dishes' information in a central database and enable its data to be recorded digitally.
Photo: PATH/Mundia H Masuzyo
The entomology lab technician then places the mosquitoes under microscope to separate out mosquitoes in the genus Anopheles—the only genus of mosquitoes that can carry and transmit malaria—from other mosquitoes.
Photo: PATH/Mundia H Masuzyo
"The interesting part about this job is that we are able to identify the diverse species and we are part and parcel of a community that is fighting against malaria," says Paul Sakala, an entomology lab technician on the PATH ATSB project.
Photo: PATH/Mundia H Masuzyo
Though the tiny mosquitoes may look identical to the untrained eye, the lab staff are able to not just distinguish Anopheles from other genera of mosquito, but can even tell the different species of Anopheles apart!
They use clues like stripes and markings, wing patterns, antennae, body shape and leg position, and more to identify the species of each Anopheles mosquito on the tray, and record how many of each they found.
"In this ATSB study, I have come across a number of Anopheles species, such as Anopheles funestus, Anopheles gambiae, Anopheles coustani, Anopheles tenebrosus, and Anopheles squamosus just to mention a few," recalls PATH entomology lab technician Mwaba Manda.
Photo: PATH/Mundia H Masuzyo
Though as many as 40 Anopheles species can carry and spread malaria, some of the most common in Africa include include An. gambiae s.l., An. funestus s.l., and An. arabiensis.
Photo: PATH/Mundia H Masuzyo
Finally, mosquitoes are sorted by male and female. Only female Anopheles mosquitoes take blood meals from hosts, so only they—and not males—transmit the malaria parasite.
How can they tell which is which? "The difference between a female and a male Anopheles mosquito is that males have bushy, hairy antennae, while the antennae of females have few hairs," explains PATH entomology lab technician Mercy Mukopole.
Photo: PATH/Mundia H Masuzyo
After taking careful notes on the mosquitoes' appearance, species, and—in the case of female mosquitoes—whether or not they have blood fed, the entomology lab technician places the mosquitoes in a tube for preservation.
Photo: PATH/Mundia H Masuzyo
"We put mosquitoes in an Eppendorf tube containing cotton wool and silica gel, which acts as a preservative by absorbing moisture, thereby preventing decay," says PATH entomology lab technician Christopher Malundu.
Photo: PATH/Mundia H Masuzyo
Once they're ready for storage, each tube is labeled with a unique sample ID QR code, and its data are input into the central database.
Photo: PATH/Mundia H Masuzyo
Later, an entomology lab technician will be able to scan the QR code on the tube to access information on that mosquito.
Photo: PATH/Mundia H Masuzyo
Finally, once all of the tubes are labeled, data recorded, and QCs complete, the mosquitoes are placed into a freezer for future molecular analysis.
Photo: PATH/Mundia H Masuzyo
So many mosquitoes come through the lab—how does the staff make sure that they are recording high quality data? It's simple—they check each others' work!
Photo: PATH/Mundia H Masuzyo
Quality control specialists like PATH entomologists Patricia Mambo and Benjamin Chanda are on the team to do spot checks. They ensure that data recorded in the field are reported accurately and mosquitoes are identified correctly.
Photo: PATH/Mundia H Masuzyo
"Angela, it seems you have a lot of mosquitoes here! Which mosquito is this?" asks PATH entomologist Benjamin Chanda.
"That's an Anopheles funestus," replies entomology lab technician Angela Tobolo, who performed the initial identification of the mosquitoes.
"Thank you. How do you know it's not Anopheles gambiae?"
"Anopheles gambiae has speckled legs and one pale spot on the 2nd and 3rd main dark areas. Funestus has only one pale spot on the 2nd main dark area and solid, dark legs. I also confirmed using a key that this is funestus."
"Excellent! I agree with you that this is Anopheles funestus."
Members of the PATH Kaoma Lab team show off the tools of their trade. Left to right: Entomology lab technicians Memory Chikwanda, Asah Kalemba, Angela Tobolo, Mwaba Manda, and Mercy Mukopole. Photo: PATH/Mundia H Masuzyo
Thanks to the talented entomology team at the PATH Kaoma lab, PATH technical experts and the Zambia National Malaria Elimination Centre have critical information they need to better understand malaria in Zambia!
With a partnership spanning across disciplines—from the entomology collectors in the field, to technicians and modelers in the lab, all the way to decision makers and implementers at the Ministry of Health—this group effort is helping drive progress towards a malaria-free Zambia.
