Andy Ransom, CEO of Rentokil Initial, discusses the threat from mosquitoes worldwide and Rentokil’s commitment to protecting people and enhancing lives through our vector control work.
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Mosquito-borne diseases have been recorded in human history for thousands of years as major causes of disability and death. No one, however, realised mosquitoes were vectors of the diseases until the end of the 19th century. The first breakthrough came in 1877 when British doctor Patrick Manson discovered that a Culex species of mosquito could carry the human filarial roundworm.
Over the next two decades he and other researchers from France, Italy, Russia and the USA turned to malaria, a major killer in both tropical and temperate countries. They slowly completed the complex jigsaw of malaria transmission and biology in humans and mosquitoes.
In 1894, Manson persuaded Ronald Ross, a medical officer in the Indian Medical Service, to study mosquitoes as the likely vector of the malaria parasite. After years of fruitless research Ross finally proved in 1897 that Anopheles mosquitoes could carry the malaria parasite. He called the day of his discovery, 20 August, 1897 “Mosquito Day”. The London School of Hygiene and Tropical Medicine later named 20th August World Mosquito Day to mark the significance of his discovery, which is celebrated annually.
This critical link to the Anopheles mosquito also showed that practical measures to prevent mosquito bites and control mosquito populations — vector control — could be used to prevent malaria.
Many mosquito-borne diseases such as malaria, dengue, Zika, chikungunya and West Nile fever have been undergoing a resurgence in recent years. WHO Director General Dr Margaret Chan told UN member states at the Sixty Ninth World Health Assembly in 2016 that: “Above all, the spread of Zika, the resurgence of dengue, and the emerging threat from chikungunya are the price being paid for a massive policy failure that dropped the ball on mosquito control in the 1970s. … Let me give you a stern warning. What we are seeing now looks more and more like a dramatic resurgence of the threat from emerging and re-emerging infectious diseases. The world is not prepared to cope.”
To revitalise vector-control efforts worldwide and emphasise to the world that action needed to be taken urgently WHO developed a new global strategy for vector control in 2017.
Rapid urbanisation, increases in international trade and travel, climate change and changing agricultural practices are all contributing to the increases in mosquito and other vector-borne diseases. History shows that vector control efforts need to be continuously supported by all countries to maintain expertise and capacity. This is essential to detect threats, prevent resurgence of deadly diseases and cope with new outbreaks of diseases.
Read about the wide range of policies and practical measures needed for effective control of diseases such as dengue, malaria and Zika
Malaria is the deadliest mosquito-borne disease. In 2016 there were an estimated 216 million cases and 445,000 deaths in 91 countries, according to WHO. It is mainly a disease of under-developed rural areas with poor public health infrastructure.
Malaria is caused by Plasmodium parasites transmitted by Anopheles mosquitoes. There are five species of the parasite that cause malaria and over 40 species of Anopheles mosquitoes that are important vectors of the disease. Each species of Anopheles has distinct ecology and behaviour, which makes malaria vector control more complex than other mosquito-borne diseases.
Rentokil Initial has actively supported the charity Malaria No More since 2011. The charity supports malaria prevention projects in countries such as Nigeria, Ghana, Botswana, Namibia and Kenya.
Rentokil Initial has raised over £180,000 to date. Colleagues have come up with many ideas to raise funds including bike rides, mountain climbs and cake bakes.
In 2015, to celebrate our 90th anniversary we held an event in the House of Commons in London and presented Malaria No More with a cheque for £30,000.
The Zika virus was first identified in 1947 in a rhesus monkey in Uganda. Up to 2007 it was regarded as a mild disease having only 14 documented cases and no hospitalisations or deaths. In 2007 the first serious outbreak occurred, on the Pacific Island of Yap, then in 2015 it erupted first in Brazil, South America and the Caribbean. By May 2017 84 countries had reported Zika infections and scientists had confirmed a link with serious neurological conditions.
The virus is primarily spread through bites of infected Aedes species of mosquito, including Ae. aegypti and Ae. albopictus, but many regions have local Aedes species that can transmit the virus. The virus can also be transmitted from a pregnant mother to her foetus, through blood transfusions and through sex. The experience of the recent Zika outbreak showed the importance of an integrated approach in controlling the outbreak that should include integrated vector management, risk communication, sexual and reproductive health services, health education and healthcare.
Dengue is considered to be the most important mosquito-borne viral disease worldwide because of its rapid spread in recent decades, resulting in it now being endemic in more than 100 countries. “Explosive outbreaks” are occurring in new areas and local transmission has even been recorded as far north as France and Croatia. The number of cases is vastly underreported because many countries do not have the capability to monitor cases.
Dengue thrives in the poor urban areas of the tropics and subtropics because of poor sanitation and the many sites suitable for breeding. Aedes mosquitoes only need a small quantity of water for the larvae to develop, such as gutters, puddles, drains, bottles, cans, tyres and uncovered water containers.
It is not restricted to those areas, however, as the Aedes vector mosquitoes are well adapted to the human environment and can breed where there is better sanitation and quality of housing if vector-control methods are neglected. Even the most expensive housing areas can have suitable breeding sites such as plant pots and badly draining gutters.
Find out about the wide range of policies and procedures needed to effectively control diseases such as dengue, malaria and Zika