Photo diary: A day in the life of Malaria mosquito collectors

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.

To do this successfully, the researchers need to trap mosquitos. This helps them study mosquitoes' abundance, biting frequency, and more. PATH's ATSB entomological surveillance team is responsible for collecting mosquitoes that can transmit malaria.

Most entomological—or "ento"—collections are conducted between 6 PM and 6 AM. However, data from the ATSB Trial in Kaoma in Zambia's Western Province showed that malaria mosquitoes were still active before and after normal ento collections. Knowing that malaria rates remain high in Kaoma despite strong coverage with bed nets, the team wanted to study whether daytime biting could be occurring outside the normal mosquito collection window. If so, it would have important implications not only for research studies, but also for the effectiveness of existing vector control tools.

This is why PATH's ATSB ento surveillance team conducted a series of collections spanning a full 24 hours rather than the usual 12.

We tagged along for one of the 24-hour ento collections to learn more about what goes into this important and unusual job.

There is much work to be done before the collections can begin. All the supplies for the 24 hours of collections for 10 collection teams—including Centers for Disease Control and Prevention ultraviolet (CDC UV) light traps, aspirators, sample cups, and tablets for entering data—must be assembled into coolers, loaded into trucks, and brought to the central meeting point.

Before going out to collect mosquitoes, all ento collectors must take a malaria rapid diagnostic test, or “RDT.” Those who are found to be malaria-free receive antimalarial medicine to protect them while they are in the field. Those who are found to have a malaria infection receive treatment to clear the disease and are not eligible to participate in mosquito collections in that month.

The ento collectors then divide into pairs and head to their assigned households to gather consent to participate in the study from the families who live there. Each household has been randomly selected to participate in the study.

Meet Joseph Chola Sainent and Amazing Kiyaka. They are the ento collection pair who will be working the night shift for this collection. Joseph and Amazing introduce themselves to the homeowner, explain the study, and ask for consent to collect mosquitoes inside and outside their home.

"Hello! We are coming from PATH to do our collections of mosquitoes," says Joseph. "According to our map, this house has been picked for Human Landing Catch."

Now that the homeowner has agreed to participate in the study, the pair can begin setting up their gear for the collections. They label the sample cups that will hold each hour's set of mosquitoes and ensure the traps are clean and intact.

The team will compare collections made simultaneously using two commonly used methods both inside and outside the home: CDC UV light traps and the Human Landing Catch (HLC).

CDC UV light traps are used to trap mosquitoes in and near households, as well as at locations away from homes. CDC UV light traps allow for collection of indoor and outdoor host-seeking mosquitoes with minimal exposure risk to the collector. Mosquitoes are attracted to odor cues from household residents and a UV light on the trap and are sucked into the collection cup by a fan as they approach the trap.

The ento collectors hang the CDC UV light traps inside and outside the home so that the trap’s fan is about 1.5 meters off the ground.

The second method, Human Landing Catch, or HLC, is the gold-standard method for collecting human host-seeking mosquitoes. In each pair of ento collectors, one is responsible for collecting mosquitoes by HLC indoors, and one collects outdoors.

During HLC, the collector waits and watches carefully for mosquitoes attracted by their odor and body heat to land on their exposed lower legs. In order to prevent bites on places other than the lower leg, all ento collectors are required to wear closed-toed shoes, shorts or loose trousers rolled to the knee, and a long-sleeved shirt.

As soon as a mosquito lands, before they can bite...

the collector sucks the mosquito into the aspiration tube,

and transfers it to a collection cup.

"So what I'm doing here is that I'm waiting for mosquitoes to land on me and then aspirate them. Then when I put them in my aspirator, I'll need to put them in my collection cup."

The ento collectors use their tablet to record GPS coordinates and altitude of the collections, collection methods used, and the status and functionality of the equipment being used.

"The time is 19:45. It is another time to enter data into the Comm Care [tablet]," says Amazing. "I enter data at every 45th minute of every hour throughout the whole collection."

Periodically throughout the collection, the team changes the HLC collection cup. The collection cup on the UV light trap is replaced every two hours during daytime collection. The cups are left in place throughout nighttime collections, though are spot checked twice during the night.

Once they have been used, collection cups are stored in humidified coolers.

Once an hour, the team takes a short break to stretch and drink tea or coffee. "The challenge we find with this job at night is that we catch mosquitoes using an aspirator all night without sleeping."

The caffeine and sugar help them stay alert through the early hours of the morning.

Throughout the night, PATH entomology staff stop by to visit Joseph and Amazing, double-checking that collections are adhering to the study protocol and standard procedures and that the equipment is operating correctly.

Over the course of the night, the cups in the cooler fill with mosquitoes...

...until the night shift comes to a close and their cups have all been filled.

Joseph and Amazing begin the process of getting the collection site ready for the day shift team to arrive.

"The night shift has come to an end, so I'm putting the day shifts' cup up."

They scan the labels on the coolers with their tablet to ensure their samples are connected to the data they input over the course of the last 12 hours.

Then the day shift arrives to take over for the next 12 hours.

“Hello. I'm Nawa Kayangula I'm with my fellow ento collector, Kuzwayo Tembo. This is 6 AM and we will be working through the day, up to 6 in the evening.”

Joseph and Amazing head back to the field stations to return their equipment and mosquito-filled coolers and load their samples into the truck to be sent to the laboratory for further processing. It's now time for them to get some well-deserved rest!

In the meantime, Nawa and Kuzwayo are back at the collection site, continuing to collect mosquitoes inside and outside the home.

During the day, the team has the opportunity to speak more with the house's residents about their work.

"The good part of this job is that it has helped me know people that I have never met and teaching people how malaria is transmitted," said their fellow ATSB ento collector, Michelo Moosho.

"How do you feel about this CDC light trap? How are they working?" asks Nawa.

"I feel it is working," says the resident. "Since the time it was put here, you can see mosquitoes in that cup. So, I feel it is working."

"In the places we go to work people ask us, ‘These CDC light traps you put in our homes, won't they make us have bad dreams?’ We tell them no, that they catch mosquitoes near your homes," said ATSB ento collector Brian Lukonde.

"Yes, we tell them we come to put the light traps so that mosquitoes can follow the light inside and enter in the cup," agreed Michelo.

Nawa and Kuzwayo continue to collect mosquitoes during the day by HLC and with the CDC UV light trap, periodically stopping for a well-deserved tea break.

Nawa and Kuzwayo replace the collection cups in the CDC UV light trap every two hours. Before changing the cup, the ento collectors ensure that all the mosquitoes are on the bottom of the trap and tie the neck of the collection bag. This prevents mosquitoes from escaping and being damaged when the bag is removed from the trap.

Mosquitoes may bite less frequently during the late morning and afternoon, but it's just as important that the day shift team and entomology staff stay vigilant, checking traps and recording accurate, timely data every two hours.

"I’m getting the GPS location so I have that information for the hourly form for HLC."

Sometimes the equipment needs maintenance to ensure it's working properly.

"I'm here for spot check. This is 11:52 AM and I've noticed that the battery isn’t running. So I'm changing the battery!"

As soon as the battery is replaced, a whirring noise begins and the CDC UV light trap is functioning once again.

Another team member brings Nawa and Kuzwayo lunch at noon, and the team takes a break to eat.

"Yes ma guys! [Hello guys!]"

"Enisha! [Hey!]"

"Musebezi uzayamaya cwani? [How is the work going?]"

"Uzayamaya fela hande, luitumezi! [The work is going well, thanks!]"

Daytime field supervisors stop by throughout the day to conduct more spot checks, checking samples and equipment outside and inside the home.

"It is 2 PM and both HLC and CDC collections are in progress. Afternoon collections are important!"

At 6:00 PM, the day shift ends. The team packs up the equipment and thanks the homeowner for their participation.

"Bye! Thank you so much for your hospitality and for your company."

"It has been a pleasure having you people at my home. I enjoyed it so much. My perception is this is a very good approach towards malaria prevention. Thank you."

The day shift logs their final data and regroups with the rest of the ento collection teams to turn in their equipment and samples for processing.

"This job is important because we catch mosquitoes, and they are taken to the laboratory. Then people from the laboratory work on them so a decision can be made to reduce malaria," said ATSB ento collector Brian Lukonde.

And with that, the 24-hour ento collection in Kaoma is finished, but the ento collectors will still have more work to do to complete their study! To get a full picture of when and where the mosquitoes are biting, they will also need to perform collections in public places like schools and the market, as well as in rural areas further away from concentrated groups of people.

Keep your eye out on the path.org and @PATHMalaria to continue following along with the ento collectors’ work to end malaria in Zambia!

Special thanks to Mundia H Masuzyo, Patricia Mambo, Chama Chishya, Benjamin Chanda, and the whole ATSB team.