Mosquitoes: friend or foe?

They kill more people on a yearly basis than any other animal. They are public enemy number one, with 2 million victims per year. They are mosquitoes, and we do everything in our power to reduce their numbers.

In this light, every weekday at 07:00 a bus drives to the south-eastern Brazilian city of Piracicaba with a special load: mosquitoes. More than 100.000 of these animals are released and go in search of mates.

But these are no regular mosquitoes. They are genetically modified in order to pass on a deadly genetic trait to their offspring who die before ever reaching adulthood.

This approach has been tested in small batches and it seems to reduce the spread of mosquitoes by over 80%. This might sounds like good news, but it might also be dangerous to disturb the balance of nature, as we do not know what the negative consequences could be. I think of the teachings of Silent Spring, in which Rachel Carson showed the detrimental effects of indiscriminate pesticides on insects, and their predators, the birds, which consequently turned that spring into a “Silent Spring”. But what alternatives do we have?

What are the alternatives to genetic modification?

New efforts still need to prove their worth and it will take years before they can be measured at meaningful level. In addition, any alternative against mosquitoes, such as a vaccine against the disease that they carry, including Zika, is not expected in the short term.

As a consequence, experts say that the best solution is the use of traditional methods to avoid mosquitoes. In other words: reduce the risks of being bitten by wearing long sleeves and using repellents. Unfortunately, the latter can be very harmful to the skin and the environment – the same accounts for the DDT pesticide which is forbidden in many, but not all countries due to causing ecological and irreparable damages.

It seems that on issues related to mosquitoes, human interests, as opposed to animal and environmental interests, are considered more important. Mosquitoes have certainly never been in a privileged position. But then again, they carry many deadly diseases, such as the Zika virus.

The Zika virus (ZIKV)

There are around 20 different types of mosquitoes in the Netherlands. The majority feed only on nectar and pollen. From the species that bite us, only the female mosquitoes feed on human blood. At present, it is just annoying to be stung in the Netherlands. In Latin America and in other countries there are bigger issues when it comes to mosquitoes bites; it is the risk of disease.

The main mosquito that transfers ZIKV, dengue fever, chikungunya fever, and yellow feveris is the Aedes aegypti, an exceptionally cunning foe. It gives preference to urban areas and primarily stings humans, which increases the spread of diseases amongst humans. In addition, Aedes aegypti feeds during daytime and breeds in small wet spots, such as flowerpots, cans, and tires that collect (stagnant) rainwater.  In order to combat these mosquitoes, it is essential to stop their reproduction, which can be done by minimizing the amount of breeding sites.

Currently, most diseases spread by mosquitoes are hard to treat. Women in Zika infected areas are even encouraged to avoid getting pregnant, as the virus is heavily linked to babies being born with deformations of the head and brains, which is called microcephaly. In a cruel paradox way, it seems that nature is balancing itself out: human populations are reduced by the increased spread of deadly diseases carried by mosquitoes, which are increasing in numbers due to climate change, which is instigated by humans. Thus, might Rachel Carson be right again? Are we to expect another Silent Spring, if we cannot find alternative ways to combat the mosquito?

Silent Spring

Silent Spring (1962) by the late Rachel Carson is one of my favorite books. Her goal was to make the public aware that nature is vulnerable to human intervention. Carson radically suggested that technological advances need to be contained as they are fundamentally in breach with the natural processes.

The threats, as portrayed by Carson (contamination of the food chain, cancer, genetic disorders, and the extinction of entire species) were, at that time, too frightening to be neglected. For the first time, it was generally accepted that it was necessary to regulate the industry in order to protect the environment, and consequently environmental activism was born. I think that this book should again start occupying a prime position on people’s reading lists. Furthermore, I believe we need to take notice of the threats mentioned by Carson. We need to avoid another Silent Spring, not only for the benefit of the mosquito but in the interest of all animals – ourselves included.