Entomology Today

Genetically Engineered Mosquitoes Reduce Dengue Transmitters by 95 Percent

2006 Prof. Frank Hadley Collins, Dir., Cntr. for Global Health and Infectious Diseases, Univ. of Notre Dame This 2006 image depicted a female Aedes aegypti mosquito as she was obtaining a blood-meal from a human host through her fascicle, which had penetrated the host skin, was reddening in color, reflecting the blood’s coloration through this tubular structure. In this case, what would normally be an unsuspecting host was actually the CDC’s biomedical photographer’s own hand, which he’d offered to the hungry mosquito so that she’d alight, and be photographed while feeding. As it filled with blood, the abdomen became distended, stretched the exterior exoskeletal surface, causing it to become transparent, and allowed the collecting blood to become visible as an enlarging intra-abdominal red mass. Dengue is a viral disease transmitted by urban Aedes mosquitos, principally A. aegypti, a species found living in close association with humans in most tropical urban areas. Mosquito biting activity is greatest in the morning for several hours after daybreak and in the late afternoon for several hours before dark. It may feed all day indoors, in shady areas, or when it is overcast. This mosquito breeds in artificial water containers, such as discarded tires, cans, barrels, buckets, 55 gallon drums, flower vases, and cisterns, all frequently found in the domestic environment. Since 1980, the incidence of dengue has increased dramatically in tropical countries worldwide, with endemic and/or epidemic virus transmission documented in most countries of the Caribbean Basin, Central and South America, the Pacific Islands, Asia, and Africa; many countries have had multiple outbreaks. Epidemics are frequently not reported because of inadequate disease surveillance.

The results of a trial of genetically engineered mosquitoes intended to reduce their ability to transmit dengue fever have been published in the journal PLOS Neglected Tropical Diseases.

The mosquitoes, commonly known as “Friendly Aedes aegypti” mosqitoes in Brazil where the trial took place, were developed by a company called Oxitec.

The results of the trial showed that the numbers of the mosquito (Aedes aegypti) that spreads dengue fever, yellow fever, chikungunya, and zika virus were reduced by more than 90%.

“The fact that the number of Aedes aegypti adults were reduced by 95% in the treatment area confirms that the Oxitec mosquito does what it is supposed to, and that is to get rid of mosquitoes,” said Dr. Andrew McKemey, head of field operations at Oxitec. “According to published mathematical models reviewed and recommended by the World Health Organization (WHO) working group on dengue, it would also reduce the number of biting mosquitoes below the disease transmission threshold. The next step is to scale up to even larger studies and run mosquito control projects on an operational basis.”

The study, which took place in the Itaberaba neighborhood of Juazeiro city in Bahia State, was led by the University of São Paulo and Moscamed, a company that specializes in environmentally friendly pest control. The treatment area included a population of approximately 1,800 people.

How it works

This method of control is species-specific. The Oxitec male mosquitoes are released to mate with the pest females, and their offspring die before they can transmit the disease or reproduce because of a self-limiting gene. The mosquitoes also carry a color marker for monitoring, and the insects and their genes do not persist in the environment.

Mosquito control in Brazil

“This invasive mosquito and the diseases it carries is a real challenge,” said Professor Margareth Capurro of São Paulo University. “Aedes aegypti is developing resistance to insecticides, and even when we remove breeding sites they continue to reproduce and transmit diseases because they live in areas that are difficult to treat. This is why we need new tools. We knew that the Oxitec mosquito was a promising tool, so we wanted to independently evaluate its effectiveness here in Brazil.”

Dengue, chikungunya, and zika virus are debilitating diseases. There is currently no vaccine or specific medication for any of them. According to the WHO, the only way to combat dengue at present is to control the mosquitoes that spread the disease.

Read more at:

Suppression of a Field Population of Aedes aegypti in Brazil by Sustained Release of Transgenic Male Mosquitoes