World Mosquito Day on 20th August, marks the historic discovery by British doctor Sir Ronald Ross in 1897 that female Anopheles mosquitoes transmit malaria between humans. It aims to raise awareness about the causes of mosquito-borne diseases and the continuing struggle to eradicate this and other debilitating diseases spread by mosquitoes as more than half of the world’s population live in areas where the mosquito species present can spread disease.
In recent decades some mosquito-borne diseases have seen a resurgence, from Zika, Dengue, West Nile fever to chikungunya. Even malaria, which has had long-term global efforts to eradicate it has held on stubbornly adapting and resisting attempts to eliminate it. Which is why Rentokil UK continues to support our chosen charity Malaria No More UK in their endeavours to end malaria.
Many of these diseases have no specific treatment and the limited medicines available for some are facing resistance. The insecticides used to control these insects are also facing increasingly resistant mosquito mutations as they adapt to survive. So it seems innovations are urgently needed to control old diseases and prevent new ones from spreading.
The science and technology to fight against mosquito-borne diseases.
Scientists in fields as diverse as biochemistry, genomics, entomology, computing, remote sensing, avionics, artificial intelligence, robotics and aerospace engineering are combining their resources to develop new ways to fight mosquito-borne diseases. The hope is that their dedicated research will help to provide a new dawn in the fight against the global threat of mosquito-borne diseases.
Fighting Insecticide Resistance
In recent decades Anopheles and Aedes mosquito populations in many parts of the world have built up resistance to some of the available insecticides and larvicides used for vector control. The IVCC (Innovative Vector Control Consortium) highlights that its been 30 years since pyrethroids were introduced as a radical new anti-malaria insecticide and resistance to pyrethroids in the major vectors of malaria poses the greatest current threat to malaria control. Insecticide resistance can occur at a low frequency for many years until a ‘tipping-point’ is reached, when resistance rises extremely rapidly.
Two new-generation insecticides were approved by WHO in 2017 and are being distributed in malaria areas for use in IRS (indoor residual spray) programmes by the NgenIRS project. Since 2016 the project has supported operations in 12 African countries. Its hoped that by 2019 at least 26 million people in Africa will be protected.
New odours to attract and repel mosquitoes
Mosquitoes find human hosts by sensing the carbon dioxide we breathe out. But when they get close enough they locate the best sites for feeding by detecting volatile chemicals given off by human skin moving toward exposed areas such as ankles and feet.
Researchers at the University of California Riverside discovered that he very receptors the mosquito’s use to detect carbon dioxide are the same ones that detect skin odors as well, thus explaining why mosquitoes are attracted to — smelly socks, worn clothes, bedding — even in the absence of CO2. They used modern chemical screening techniques to test half a million compounds in a chemical database to find those that could trigger mosquito sensing organs.
They chose to concentrate on two compounds that are already in common use, so don’t need lengthy and costly safety testing, to study further:
- ethyl pyruvate – which is a food flavouring with a fruity flavour: this was found to reduce Aedes aegypti attraction
- cyclopentanone – a mint-smelling flavour and fragrance: this was a powerful attractant for Culex quinquefasciatus mosquitoes
By inhibiting the cpA neuron, ethyl pyruvate was found in their experiments to substantially reduce the mosquito’s attraction towards a human arm. Whilst by activating the cpA neuron, cyclopentanone served as a powerful lure (like CO2) attracting mosquitoes to a trap. These ‘mask’ and ‘pull’ strategies could be used in a complementary manner, wherever mosquito-borne diseases are endemic.
Medicines for Malaria Venture (MMV) a leading product development partnership has a network of over 400 pharmaceutical, academic and endemic-country partners across 55 countries developing drugs to protect against malaria. Since its foundation in 1999 the network has brought seven new medicines to market that are already being used to prevent and treat the disease. As recently as July this year the US FDA endorsed tafenoquine (a medicine produced under the programme) which targets the dormant liver stage of Plasmodium vivax and is the first new medicine for 60 years for this type of treatment.
The future fight against mosquito-borne diseases
There is so much effort and dedication in the tireless work towards the future of controlling mosquito-borne diseases, the outlook is more promising as scientific developments across many disciplines are providing new ways of treating diseases and controlling mosquitoes.