Skip to main content
Markkula Center for Applied Ethics

CRISPR: Next-Gen Mosquito Zapper?

Puzzle pieces of DNA

Puzzle pieces of DNA

Madeline Eiken

Madeline Eiken was a Hackworth Fellow for the 2018-2019 school year. She graduated from Santa Clara University in 2019 where she majored in bioengineering and minored in chemistry. She was awarded the Ethics Center Markkula Prize in June 2019. She currently works at Allosource, a tissue bank in Colorado.

Mosquito-borne diseases are a major concern in many parts of the globe. Diseases that spread to people via mosquitos, including Zika virus, West Nile virus, dengue, and malaria, have serious negative impacts on human health.

A company we’ll call Kill-M, has utilized CRISPR technology to create a mosquito that will prevent the spread of mosquito-borne diseases by reducing the number of breeding mosquitoes--fewer mosquitos, fewer bites; fewer bites, less disease. Using CRISPR, male mosquitos are genetically modified so that their offspring die before reaching sexual maturity, thus decreasing the mosquito population.

This technique to reduce the insect population is called the “sterile insect technique,” which ordinarily involves sterilizing insects such as the screw worm and the Mediterranean fruit fly using radiation, not genetic engineering. Radiation is generally quite successful, especially at eliminating invasive insect species. But, radiation kills mosquitoes, so CRISPR technology, rather than radiation, is used to edit mosquito genes.

Ecologists have expressed concern at the use of the sterile insect technique to eradicate local insect populations. Eliminating a species of insect like mosquitoes reduces local biodiversity, which is concerning because it accompanies wider trends in decreasing global biodiversity. The elimination of an insect species can also influence other areas of the environment, such as predators who eat the insects or plant species that need to be pollinated.

Identify the stakeholders impacted by use of the sterile insect technique. Does one group have a larger stake in the potential outcome than others? Should our consideration of stakeholders be restricted to people or include animals and the environment?

Now, consider this: In Brazil, there is an urgent outbreak of Zika, a serious illness with no vaccine for prevention or cure once contracted. The symptoms of Zika are usually fairly mild, and may include fever, muscle soreness, headache and rash. Zika is not deadly, and symptoms will usually clear up in about a week without medical intervention. However, Zika is a concern for pregnant women, because the infection can be passed to her fetus causing severe birth defects including severe brain development issues, notably, microcephaly. Kill-M has been asked by the Brazilian Department of Public Health, SUS, to bring their CRISPR sterile insect technology to Brazil in order to eliminate the mosquito population and stop the spread of Zika.

It is unknown what degree of reduction in the mosquito population is required in order to make a positive impact on human health in Brazil (or elsewhere). In order to ensure success of the project and eliminate the spread of disease to pregnant women, Kill-M plans to release enough genetically modified mosquitoes to wipe out the entire native population of mosquitoes within six months.

Scale is an important consideration for engineers and scientists. Is there an ethical difference between significantly reducing the mosquito population and completely eliminating it, assuming that elimination is significantly more effective at reducing Zika infections than merely decreasing the number of mosquitoes? What are the intended and unintended consequences of the widespread elimination of the native mosquito population?

There is significant uncertainty about the long-term outcomes of releasing a population of genetically modified mosquitoes into the environment in response to Zika in Brazil. Predator species like bats, which are critical to the ecosystem, may be negatively affected by losing a food source. Additionally, mosquitoes are pollinators, so their elimination from the environment may negatively affect native flora and farming in Brazil.

Are the ecological risks and uncertainties associated with using CRISPR technology justified by the potential benefits to human health?

There is a significant amount of uncertainty about the moral status of mosquitoes. Moral status is a concept that determines whether something has intrinsic value, and should be treated with special regard. Humans have very high moral status, while pebbles have much lower moral status.

Do mosquitoes have any moral status in this case? How does their moral status compare to the moral status of the Brazilian people who may be infected with Zika?

Now consider another potential application of the CRISPR technology. A wealthy neighborhood in Florida has decided that they want to hire Kill-M to wipe out the mosquito population in their community. The mosquitoes in this region are not disease vectors, rather, they are simply annoying pests. The residents argue that insect repellants are unpleasant and ineffective. The promise of a mosquito-free vacation will increase the number of visitors to the community, and increase revenue from tourism in addition to increasing the comfort of year-round residents.

Is there any difference in the morality of eliminating the mosquito population in Brazil and Florida, given that both approaches benefit members of the community? Why or why not?

There are several reasons why some people are at greater risk of being bitten by mosquitoes than others. These can include: the bacterial population on the skin, how much someone is sweating, a person’s blood type, and the presence of certain genetic markers. Suppose the FDA has recently approved a pill that makes people completely repellent to mosquitoes. By taking the inexpensive pill once a day, residents and tourists can completely avoid mosquito bites. However, there are some mild, but unpleasant, side effects including a risk of unusual bleeding and a drop in blood sugar associated with taking the pill. People on blood thinners or who are taking insulin for diabetes should use extreme caution in taking this medication for more than a day or two. Environmental activists argue that despite the risks, the town in Florida should take this drug instead of eliminating the mosquito population.

Does the presence of this drug change your thinking about the morality of reducing the mosquito population using CRISPR in Florida? What about in Brazil?

 

Aug 28, 2019