On World Malaria Day (25 April) we acknowledge and celebrate all those who are committed to tackle malaria. This day also reminds us that malaria is transmitted by mosquitoes, the world’s deadliest animal. Despite this, the study of mosquitos – their identification, susceptibility and behaviour – has lacked focus on the science that helps us understand them: entomology.
The problem is there are few field-based medical entomologists, likely because the specific technical training is not as attractive as other streams of work. It is also a labour intensive, field-oriented career that is not suitable to everyone. But without entomology and entomologists, it is difficult to ensure that interventions are correctly targeted to have maximum effect.
The lack of investment in training a new generation of medical entomologists has been widely recognised and has been, in some cases, identified as a bottleneck towards the control and elimination of malaria and other vector-borne diseases.
Some countries particularly struggle to find qualified personnel with basic knowledge in entomological surveillance and data analysis, which is essential for informing authorities with vital information to guide decision making.
Did you know that there are over 50 species of mosquito that are known to transmit malaria? Each have their ecological niche. Among them different species prefer to breed in different places, such as clean or dirty water, small containers, ruts in the roads or lakes, and some even in estuarine / brackish water.
Some species of mosquito will prefer to bite during the day, others in the evening or deep in the night, rest indoors or outdoors, prefer biting certain animals over humans. We also now know that these preferences change over time and a species may become more or less prevalent as urbanisation or climate change alter environments. Each of these factors need to be considered when deciding on interventions, so that they can be targeted effectively as it takes just one bite from an infected mosquito to transmit malaria.
Most crucially we need to know what insecticide the mosquitos are susceptible to, as insecticide resistance is now a major problem for malaria control programmes particularly in Africa. It is vital to know about the species of mosquito in target areas, and what insecticide or intervention(s) will be best at reducing the mosquito population and have an epidemiological effect on malaria cases.
Training medical entomologists and increasing entomological capacity is not only a need, but also a duty of care. Poor entomological information leads to bad vector control decisions, leaving people unprotected and wasting limited resources.
In Angola there are less than a dozen trained and skilled medical entomologists in a country with nearly 36 million people at risk, and an estimated 8 396 000 malaria cases in 2022 – the fifth highest number globally. Here, under the Global Fund grant MENTOR is collaborating with the National Malaria Control Programme (NMCP), UNDP and World Vision to support training programmes aimed at engaging Ministry of Health (MoH) staff from provincial and municipal levels in malaria entomology surveillance efforts.
The training places a significant emphasis on providing technical capacity for field work implemented by the Malaria, Neglected Tropical Diseases and Epidemiological surveillance municipal focal points. Simultaneously, they inspire potential students to pursue advanced studies in medical entomology in regional or international reference centres.
There are good examples of the creation of medical entomological capacity in Africa. Establishing key entomological units across Africa like CREC/LSTM, has seen a major shift in entomological capacity in Africa. Qualified medical entomologists have been trained through highly specialised training then brought that capacity to countries of origin.
Reference centres have also been key to improve on time molecular and genetic analysis of mosquitoes, improving the quality of research and decentralizing laboratory analysis from global north reference centres. But such capacity needs to be expanded and transferred to other countries as such level of analysis can be done and processed at country level.
Current malaria entomological capacity is at a crossroad. While significant capacity has been created across Africa in high quality reference centres, some countries still struggle with minimal entomological surveillance. These countries still struggle to collect the most elemental data for good surveillance at scale because of a lack of technical, operational, and financial capacity – largely due to funding priorities going elsewhere.
Entomological surveillance capacity is even harder to find (and build) in conflict affected settings where entomologists are even scarcer and the sampling, collection, and analysis of mosquitoes can be neglected. This is dangerous. Unknown mosquito behaviours and susceptibility patterns often result in the inadequate and ineffective deployment of malaria control tools. Exactly what is not needed in an emergency!
In the northern province of Cabo Delgado, Mozambique, the quality of indoor residual spraying was successfully assessed despite local insecurity, thanks to a collaborative effort with the NMCP and provincial health authorities. Watch a video of this work on our Youtube channel.
The advent of machine learning models and artificial intelligence can help overcome some of the capacity gaps. Some interesting tools have been piloted to improve identification of breeding sites such as ZZAPP Malaria, to reduce the labour intensive and highly specialised work of mosquito morphological identification such as VectorCAM, or provide real time data through Smart Mosquito Traps.
These are positive developments particularly in regions where entomological capacity is almost non-existent.
But the malaria community should not look at these developments to disinvest (even more) from creating high quality entomology capacity at country level. Even the best identification models and tools cannot make day to day decisions. For this there needs to be a high level of technical entomological understanding from qualified entomologists.
In brief, more quality entomological capacity is needed in several countries, particularly in those with severe gaps of qualified entomologists. Malaria cannot rely only on satellite sciences that enable adequate diagnosis, treatment, and surveillance. Neglecting (good) entomology is neglecting the core of malaria transmission. Without it, malaria control and elimination are virtually impossible.
Caption: Surveillance training with the Ministry of Health in Angola