‘Gene Drive’ to curb malaria raises ethical questions as well

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‘Gene Drive’ to curb malaria raises ethical questions as well

Wednesday, 25 March 2020 | GYANENDRA NATH MITRA

A new technology ‘Gene Drive’ for mosquito control is currently confined to the laboratory since it raises an ethical question, if such a technology could in future be misused to the detriment of humanity.

Malaria control: Ronald Ross (1987) discovered malarial parasites in the stomach of Anopheles mosquitoes and proved that bite of female mosquitoes, transfer these parasites to humans and cause malaria. According to Cumbers (2019) half a million lives are lost annually by malaria. Other mosquitoes causing diseases are dengue, Zika, Chikungunya and yellow fever, each taking their toll of human lives and their livelihoods.

Several methods are used around the world for control of malaria. These include spray of insecticides, fumigation, destroying mosquito habitats, using bed nets for protection from their bites and many other innovations. All of these methods need to be implemented on a massive scale with sustained efforts regularly for protection from malaria. Mosquitoes and the malarial parasites they harbour have increasingly developed resistance to chemicals used for their elimination.

Recently many methods based on genetic control of mosquito population such as, use of sterile males, conditional lethal genes, microbe mediated infertility etc. have been tried but did not give desired results.

Gene drive: Andrea Crisanti and Kyros Kyron (2018), geneticist at the Imperial College, London, have developed a new method called ‘Gene drive’ for mosquito control.

Only female mosquitoes bite humans, to drink their blood as their food and produce eggs. If they are infected by malarial parasites, they pass on the parasites to the bitten person. When other mosquitoes bite the infected person, they are infected with the parasites. They transfer the parasites to other persons, when they bite them   and the chain of infection spreads to a large human population.

Crisanti and Kyron (2018) have developed a CRISPR Cas9 (Pioneer, June 20, 2018) based Gene Drive, which carries a molecular scissor called Cas9 endonuclease and a guide RNA (gRNA), which are essential for cutting the DNA at a specific site within the genome.The gene drive targets fertility genes, essential for development of female mosquitoes.Similar to humans, mosquitoes carry two copies of each gene for every trait on each pair of their DNA’s. They have altered the nucleotide sequences of one of the copies to carry the code of gene drive and a cargo DNA that causes female sterility. The Cas9 endonuclease present in the gene drive cuts the second copy of the DNA and incorporates female sterility gene through an indigenous DNA repair mechanism. When male mosquitoes mate  modified females in a normal population, they produce only sterile female mosquitoes, which cannot bite orproduce offspring. This results in a disproportionate increase in sterile females, which cannot lay eggs.

In course of time there is a collapse of the mosquito population. Their laboratory study showed that they could successfully bring the population of mosquitoes to zero within 6 months.

Theoretically gene drive once released into a fraction of population in the wild may spread nonstop to each individual in that population and beyond it and cause total elimination of the entire race.

Gene drives may also be developed to control household and agricultural pests replacing use of pesticides. It is a powerful technology, which has the potential for misuse by wrong people. With suitable modification it can be used to eliminate an entire race of animals, considered undesirable by human beings.

Gates foundation has invested more than $75 million on gene drive research at the Imperial College, London. The US military is also funding such research possibly to develop it as a biological weapon not to be brow beaten by its enemies (Brossard and others, 2019). There are no laws to prevent such misuse.

The California Cherry Board is funding research on gene drive to control invasive fruit flies that ruin their cherry crops (Regalado, 2017). It is also being considered for rodent control, wherever they have turned into uncontrollable pests.

An interdisciplinary panel discussion was held in November 2017 to examine complexities of Gene Drive application as a part of the Third Sackler Colloquium, in the University of North Carolina, USA. Social scientists, life scientists and journalists discussed the problem from each of their unique perspectives.

Journalism, especially science journalism, has an important role to play in helping the public understand complex and technical subjects, especially those that raise ethical issues. Technical assessment of risks involved in use of such a technology requires responsible decision making by multiple actors(Brossard and others, 2019).

In an article written by Jennifer Kahn in New York Times on January 8, 2020, entitled ‘The Gene Drive Dilemma: We can alter entire species, but should we?’ the author states that ‘Gene Drive’ seems almost tailor-made to tap into our worst fears: a powerful, invisible technology that spreads of its own, carrying out a fundamental transformation of nature. It’s a situation that practically invites us to imagine evil corporations on the move or secret military experiments going amok.

There are several factors which may hinder successful application of Gene Drive. The engineered insects may not survive in harshness of the wild. They may not be attractive to wild mosquitoes for mating.  Gene Drive may have to be designed exclusively for different insects taking into account their speed of multiplication and adaptability to specific environment.

What will be the impact of application of gene drive on environment if an entire species is removed from the eco-system? Several species have already gone extinct due climate change. This needs careful assessment.

However extinct of anopheles mosquitoes may not have much impact since it is one of the 3,000 mosquito species found around the world (American Mosquito control Association, 2020).

Gene Drive needs to be applied rationally for each species taking into account its overall importance to maintain diversity of an ecosystem.

Since gene drive modified organisms can spread of their own in large geographical areas, decisions need to be taken involving countries and communities who are likely to be affected.

(Dr Mitra is a former Professor and Dean, OUAT. References quoted are available in the net. gnmitra@gmail.com)

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