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PAHO Issues Warning on Vector-Borne Diseases: Time for a Bold Solution?

Mosquito sketch by Zoe Carlton

A recent alert from the Pan American Health Organisation/World Health Organisation (PAHO/WHO) has brought to light alarming statistics.

In 2023, the Americas witnessed the highest surge in dengue cases in recent memory, marking a staggering 300% increase within a year. This dramatic rise underscored the urgency to escalate efforts in combating the Aedes aegypti and the rapidly proliferating Aedes albopictus mosquitoes, the primary carriers of dengue and other deadly vector-borne diseases. 

As the Small Island Developing States (SIDS) conference convenes in Antigua with climate change high on the agenda, the Caribbean and even parts of Europe are grappling with a climate-induced surge in mosquito-borne ailments. With an estimated 390 million dengue cases annually and an upward trend in dengue, zika, chikungunya, and yellow fever incidents, immediate action is imperative.

PAHO Director, Dr. Jarbas Barbosa, has urged for intensified efforts to eradicate breeding grounds, enhance mosquito bite prevention, strengthen healthcare readiness, and educate the public. 

Meanwhile, Andrea Ammon, Director of the European Centre for Disease Prevention and Control (ECDC), has sounded the alarm on invasive mosquito species spreading across the EU/EEA, potentially leading to a surge in cases and fatalities from these vector-borne diseases. The concerning spread of diseases is closely intertwined with climate change, which facilitates the increase of mosquitoes and ticks through warmer temperatures, altered precipitation patterns, and rising sea levels.

The economic toll of these diseases is staggering, with dengue alone costing an estimated US$9 billion annually in 2013 (nearly US$12 billion today), and malaria costing at least US$12 billion per year in Africa alone. Anti-mosquito measures pose both health and financial challenges, with concerns over the toxicity of mosquito coils, limited effectiveness of fogging, and the high cost of mosquito traps. To effectively tackle this threat, concerted action is imperative, including the adoption of innovative techniques such as genetic modification and biocontrol to control mosquito populations.

Solutions?

Dr. Michael Bonsall, a population biologist at the University of Oxford, underscores the grave health implications of mosquito vector-borne diseases. As nations grapple with the daunting challenge of addressing the significant increase in these diseases, Dr. Bonsall highlights that traditional methods such as insecticides carry environmental and health risks and have proved ineffective in reducing vector-borne diseases. There are currently no drugs available for dengue and any vaccine development is likely years away. 

This leaves vector control as the most viable solution. Dr. Bonsall describes genetic modification of mosquitoes as “a tool in the box,” offering a potentially transformative approach to curtailing mosquito-borne illnesses. 

Reflecting on decades of pest eradication efforts, Dr. Bonsall points out the historical use of the pesticide DDT in Brazil during the 1950s, which significantly reduced the mosquito population and consequently dengue cases. The resurgence of cases following the ban on DDT due to its toxic effects underscores the need for more sustainable solutions. Instead of aiming for complete eradication, the focus should be on reducing mosquito populations to manageable levels, thereby alleviating the burden of vector-borne diseases on communities. 

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Genetic modification involves manipulating the DNA of organisms to achieve desired traits. In the case of mosquitoes, scientists have developed methods to render these disease vectors ineffective or drastically reduce their population. Contrary to misconceptions, Dr. Bonsall emphasises that responsible genetic modification does not pose risks to the environment or other species. Instead, it offers a targeted approach to managing mosquito populations without the need for complete eradication.

Prof. Luke Alphey, when at the University of Oxford’s Department of Zoology, pioneered a genetic modification technique that inhibits mosquito reproduction. When released into the wild, these modified males mate with females, and their offspring fail to develop into adults. This results in a targeted and gradual decline in the population of the Aedes aegyptiv and Aedis albopictus species wherever it is introduced. 

The concept, patented in 1999 and developed into a commercial enterprise called Oxitec Ltd in 2002, has been validated through field trials in Florida, Brazil, Malaysia, and the Cayman Islands. In Brazil’s Piracicaba region, the release of Oxitec’s GM mosquitoes led to a remarkable 95% reduction in dengue cases. 

Addressing concerns about ecological impact, Dr. Bonsall points out that as an alien, invasive species in most dengue-endemic countries, the eradication of mosquitoes does not harm the ecosystem and stresses the importance of prioritising human lives over perceived environmental risks. 

A Case for Antigua & Barbuda

This innovative approach holds immense potential benefits for small island states such as Antigua & Barbuda. 

Reducing healthcare costs for mosquito-borne illnesses is economically beneficial, allowing resources to be allocated to other critical areas. Improved public health boosts productivity and well-being. 

The cost-benefit analysis is compelling. A recent comprehensive study by Oxford University on dengue alone, found the average cost per clinical case to be US$793 in the Americas, while annual vector control expenses per person were US$0.765. For a population of 100,000, annual vector control costs would be US$765,000, significantly less than the US$79,300,000 per case. 

Such an initiative would enhance the islands’ appeal as a safe and attractive tourist destination, reassuring visitors concerned about vector-borne diseases. Pioneering this technology would position Antigua as a leader in the Caribbean, signalling a progressive approach to addressing public health challenges in the region. In the face of complex interplays between science, ethics, and public health, embracing genetically modified mosquitoes reflects a forward-thinking strategy, safeguarding the population and advancing regional health initiatives. 

As the global community grapples with the rapidly increasing challenge of vector-borne diseases, Dr. Bonsall’s research highlights the urgency of exploring innovative strategies such as genetic modification, alongside traditional protections, to safeguard public health while balancing ecological considerations.

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In an era of unprecedented health threats, embracing science-driven solutions is imperative to protect vulnerable populations and pave the way for a healthier, more resilient future.

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