UNDERSTANDING MOSQUITO BEHAVIOR TO STOP MALARIA

Updated: Mar 24


mosquito feeding by arm (previous technique)
The establishment of an entomology laboratory at CISM, its challenges and perspectives

25 years ago, the Manhiça Health Research Center (CISM) was created with the aim to 1) make a contribution to the fight against malaria, which was considered one of the main public health problems in the country, and 2) develop research programs that contribute to the advancement of public health knowledge with the idea to inform national but also global policies working e.g., with the World Health Organization (WHO).


At the start, CISM´s malaria research focused more on malaria epidemiology, largely ignoring the mosquito vectros. However in 2014, with the initiation of the MALTEM Program, funded by the Bill and Melinda Gates Foundation and "la Caixa" Foundation, the Center had the opportunity to introduce a new area of knowledge: Entomology.


In general, entomology is the study of insects. At the Center, the entomology laboratory unit focuses on the role of different mosquito species and their behavior in disease transmission to humans, and monitors the effectiveness of vector control tools. This involves surveillance of malaria vectors with the goal of assessing composition, density, feeding and resting behavior (when and where mosquitoes bite and rest), and susceptibility to public health insecticides. In turn, monitoring the effectiveness of vector control tools involves evaluating for example the effectiveness of house spraying as well as insecticide-treated bed nets after they are implemented by the National Malaria Control Program (PNCM) and partners.


Activities other than the aforementioned collection of "entomological intelligence" include (i) the evaluation of complementary vector control tools, such as the impact of larvicides or housing improvements on mosquito abundance, and (ii) the testing of new active ingredients that could be used in the next generation of vector control tools.

Dr. Krijn Paaijmans, Entomology PI, meeting with the team

The Center's entomology team, which currently consists of 28 workers, has been coordinated by Krijn Paaijmans since 2014. He is the Principal Investigator of the unit (also affiliated to ISGLOBAL) and currently an assistant professor at Arizona State University.


"The installation of this unit was challenging, due to the fact that there are few references of laboratory units in our country, but also because, in the Center itself, there was neither place nor adequate equipment for rearing mosquitoes”, reveals Albino Vembane, field supervisor in the entomology area. He adds that "once minimally installed, we also had insufficient inputs for the feeding of the mosquitoes themselves, since we had no artificial feeding systems for mosquitoes, having to feed them ourselves (Dr. Carlos Chaccour and I) using our arms.”


"The lack of specific training for entomologists in Mozambique is another challenge that this area faces, and that led CISM to invest in the training of several employees of the unit so that they can tackle national challenges. I´m one of those who benefited from these trainings at various levels, from short courses to obtaining my masters degree" refers Mara Máquina, the current manager of entomology. Máquina adds that it was good to have training, because due her acquired experience, she can now not only actively contribute to the expansion of entomology capacities in other sites, as was the case with the setting up of an entomology laboratory in Mopeia, Zambézia Province, but also to the training of personnel of the NMCP and partners and the creation of entomology laboratories in CISM partner organizations.


However, despite the remarkable growth of this unit, which has now established its relevance for the course of malaria studies in the country, not everyone really understands its meaning. As Luís Jamú, current entomology project assistant at CISM, tells us, “It is normal that others do not understand, because when you talk about malaria, often what comes to mind is only the mosquito that bites and causes the disease, that is, they have more information about the disease, and little information about the disease vector. And most only have the information that we capture and breed mosquitoes and accommodate them in a comfortable environment with air-conditioning and CERELAC porridge. But what research we exactly do inside our insectaries, only few know."


The establishment of any research activity within communities with its members can have its challenges, commonly regarding misinformation or misperception of the study. Albino Vembane says, "we have been misinterpreted several times by the community. For example, when we introduced the use of tents, we set traps at the entrance of the tents, and recruited adult males to spend the night inside (protected from bites by an inner tent). It was a time when there was talk of human organ trafficking, and this activity raised rumors in the community: Their wives said that we wanted to create an opportunity for organ harvesting at night. We ended up sleeping in the tents ourselves, and the next day we were able to show the mosquitoes that had been caught in our traps. Little by little the communities started participating."


Sebastião Machava, Albino Vembane and Mara Máquina

Jacob Ingaja is one of the participants who slept in a tent as part of the REACT 2 study, who revealed that "sleeping in the tent was not an easy experience due to the lack of comfort, which sometimes caused me back pain, as well as the fact that I was staying away from my family. Despite this, I could count on my family who understood the value of our participation in this study" said the participant residing in the Matutuine district.


Celso Melembe, one of the technicians of the Entomology unit insectary, argues that "gradually the community is understanding the value of our studies and methodologies, because we have contributed to the reduction in malaria cases. For example, look at the district of Magude under the Maltem project, where we contributed to the reduction of malaria by 86%. In addition to the positive feedback we receive from the community, we feel honored when research articles are published, and our data contribute to new policies and tools, as we contribute to all studies. “

Celso Melembe, Insectary Technician

"With persistent malaria transmission in several areas of Maputo province being a challenge for malaria elimination, we need to find out which mosquitoes are responsible and how to target them effectively. This includes understanding the behavior of community members, when they go indoors at the end of the day and when they go to bed, so that we can match their behavior with mosquito bite patterns", mentions the leader of the entomology team, Dr. Krijn Paaijmans. Faced with this challenge, the team believes it has the qualified infrastructure and personnel necessary to respond swiftly to challenges. "We routinely monitor mosquitoes in all three provinces in southern Mozambique, maintain a line of susceptible mosquitoes to test vector control tools, routinely perform insecticide susceptibility tests under WHO-specified conditions (27°C and 70% RH), and have the insectary and bench space to rear and identify the thousands of mosquitoes we collect annually" says the principal investigator.


"TO UNDERSTAND MOSQUITOES, WE HAD TO LEARN TO LOVE THEM"
Mosquito breeding process
“"Granted mosquito can transmit disease, but they are just the vehicle. Mosquitoes don’t make you sick, but the pathogens they carry do. But mosquitoes are intriguing insects. If you look under the microscope, many species are simply beautiful with their different spots, colors, and stripes. The same for the immature larvae: their antennae, skin and hooks are also something special, and we actually use all these features to identify them" says Krijn Paaijmans.

Due to this "love" for mosquitoes, the team has in recent years been able to deliver measurable results, most notably by adopting new approaches such as matching mosquito behavior with human behavior, which led to the discovery that many mosquito bites already happen before someone goes to bed, both outdoors or indoors. And in another study led by Dr. Mercy Opiyo, CISM’s new postdoctoral fellow, the team found that community members sometimes actively remove insecticides from their walls after the insecticide spraying teams leave. In addition, due to the local socio-economic development, new houses or new rooms are constantly being built. This leads to mosquitoes having refuges available to them, where they can avoid exposure to insecticides. This work has contributed to the awareness of the need for 1) alternative vector control tools to target mosquitoes that bite before people use a bednet, and 2) working closer with communities to make sure that they actually use bed nets and do not modify their wall surfaces shortly after IRS campaigns.


Finnaly, in recent years it has become clear that we are very close to eliminating malaria in southern Mozambique, but this goal has not yet been reached. To this end, the team will focus on the following lines of research:


1. Residual malaria transmission: It will be critical (and interesting) to find out what is happening from an entomological point of view. Do we see changes in vector species behavior or different vector species compositions after vector control? And how do we study this in pre-elimination areas, where mosquitoes are very hard to find? And if we know which mosquitoes are responsible for the ongoing persistent malaria transmisson, how do we target those residual vectors that cannot be killed with nets or indoor residual spraying?


2. New tools for surveillance and vector control: Since the end of MALTEM, the entomology unit has expanded its entomological infrastructure with an experimental hut area in Palmeira. Now there are many ongoing international efforts to develop and test new chemicals for vector control, CISM hope to play a critical role in their evaluation.


3. Other vectors present in Mozambique: Mozambique has experienced dengue outbreaks in the past, and both Aedes aegypti and Aedes albopictus have been found in Maputo province. Diseases such as dengue, zika, chikungunya, and yellow fever may be transmitted locally by these species, or perhaps this is already happening but we have not been able to detect it. "As we need to move towards integrated vector management (i.e., the rational decision-making process to optimize the use of resources for vector control), we need to rethink how we sample and control a variety of different vector insects simultaneously" comments Dr. Krijn.


Finally, mention that efforts will be maintained to continue with the training of the next generation of Mozambican entomologists. “Because we need to train the next generation of leaders in entomological research at CISM. They will be able to support CISM, or work at other national and or international research institutions. Or maybe they will be the next leaders at the Ministry of Health, the WHO, or other (inter)governmental organizations”.

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