NEW APPROACHES FOR FIGHTING EMERGING DISEASES
Frequently Asked Questions
Question 1: How important is dengue fever?
Two-thirds of the world’s population is at risk of contracting dengue fever. There are 50-100 million cases of dengue fever each year. Approximately 500,000 thousand cases of the more serious DHF/DSS occur. For more information about dengue fever, please consult the CDC website (http://www.cdc.gov/ncidod/dvbid/dengue/).
Question 2: What causes dengue fever and how is it transmitted?
Dengue fever (DF) and dengue hemorrhagic fever (DHF) are caused by dengue viruses (genus Flavivirus; family Flaviviridae). Dengue viruses are small, single-stranded, positive-sense RNA viruses. There are four antigenically-related but distinct serotypes, dengue 1, dengue 2, dengue 3 and dengue 4. Humans manifest dengue fever after being infected by the bite of an Aedes mosquito carrying any one of the serotypes. The primary infection is a severe, usually non-fatal disease. Subsequent infections with a different serotype can be much more serious. Dengue viruses are transmitted in a cycle between humans and mosquitoes. The mosquito species that is most responsible for transmitting the viruses is Aedes aegypti. There is no human to human (or mosquito to mosquito) transmission of the virus.
Question 3: What are Genetically Modified Organisms (GMO’s)?
A GMO has been defined as an organism, with the exception of human beings, in which “the genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination.” While this definition of a GMO effectively highlights the fact that the DNA is altered in a way that does not occur naturally, the definition should not be confused with the fact that the introduced DNA will is not synthesized completely de novo. Genetic material derived from natural sources is spliced together in ways that allow for the expression of gene sequences that have a desired effect. A good example of this involves the plan to express a portion of the dengue virus genome itself to activate an anti-dengue anti-viral immune response in mosquito cells.
Question 4: How will you modify the mosquitoes?
Naturally-occurring mosquitoes will be trapped from the area around the field cages and taken into the laboratory where the potentially useful genes will be introduced into them.
Question 5: Will it work?
While the researcher involved in this work are enthusiastic and optimistic about the proposed strategies, this project has the answer to this question as its primary goal.
Question 6: What are the risks involved? Is it dangerous?
The largest material risk involved in this project is that its may not succeed. Because of this, project goals of this size and scope have not been funded by government agencies and have been left to be funded by private sources.
In terms of the science, the recognized hazards have little or no risk. The types of genetic modification that will be taking place in the laboratories have been going on for decades without incident.
Scientists have come to a consensus that there is nothing inherently risky about splicing genes from one organism into another. For example, GMOs have been used for years to produce an enzyme required for processing cheese. More recently, genetically engineered rice that has the potential to eliminate vitamin A deficiencies in some human populations has been met with widespread acclaim.
Although some scientists have expressed concern about GMOs, an expert committee established by the Food and Drug Administration concluded that the safety of a food depends upon its properties, not the process used to produce it. Using this definition as a guide, the safety of any GMO must be—and is—considered on a case-by-case basis.
Question 7: Will you release any genetically modified mosquitoes into the environment?
This project does not involve the release of any genetically modified mosquitoes into the environment.
Question 8: How can you insure that modified mosquitoes won’t escape?
The large field cages used in this project are designed for maximum containment. Enclosures will be examined daily for any damage that might allow the mosquitoes to escape. Efforts include active surveillance to detect escaped mosquitoes in the immediate and adjacent areas where the cage studies are conducted. Aedes aegypti is particularly amenable to collection because it resides with humans and will readily lay its eggs in water traps (containers holding small amounts of water). Once a week, while cage studies are in progress, we will conduct a thorough survey of an area with a radius of at least 500 meters around the field station and cages. Collections will be made from structures where adult Aedes aegypti are likely to rest. Water traps will be collected once a week and any mosquito eggs collected will be tested. We will systematically remove or cover all other standing water where eggs could be laid to minimize competition for our traps from natural egg laying sites.
Question 9: What will you do if some do escape?
We will immediately conduct a control campaign to eliminate modified mosquitoes from the community. One of the criteria for an appropriate site is that it has a degree of isolation, be it geographical (e.g. an island) or ecological (surrounded by habitat inhospitable to Aedes aegypti). This will help by limiting the area where the mosquitoes could spread. An active response will include diverting project resources to implement broad-scale insecticide applications in conjunction with the local vector control personnel that will encompass at least 1 km radius around the field station. Furthermore, we will establish monitoring in adjacent communities, cities, and ports of exit from the study area/island using the techniques described above (Ques. 8). At some sites, environmental hazards (e.g. hurricanes, etc.) could threaten the integrity of containment by outdoor enclosures. If a storm or any other environmental insult threatens the field station we will depopulate the cages to prevent release of genetically-modified mosquitoes.
Question 10: How will you tell the modified mosquitoes from wild ones?
Total genomic DNA extracted from pooled mosquitoes will be tested by DNA amplification for introduced gene sequences. In preliminary studies, we will determine empirically the sensitivity of our DNA amplification screen to ensure that we are able to detect the introduced gene sequences even at low frequencies.
Question 11: Will the genetically modified mosquitoes reduce the spread of other diseases like Yellow fever or malaria?
The answer to this question varies depending on the site, disease, and genetic strategy in question. We are pursuing multiple genetic strategies to control the spread of dengue virus. Some strategies are designed to have the affect of reducing Aedes aegypti population densities and could therefore affect the transmission of other diseases for which Aedes aegypti is a vector. However, most areas have more than one species of mosquito and therefore, the reduction of Aedes aegypti population densities may have no effect on diseases that can be spread by the other endemic mosquito populations.
Genetic strategies that are designed to specifically reduce the ability of the mosquito to transmit dengue virus will not have an influence on the mosquito’s ability to transmit other diseases.
Question 12: Will genes from the genetically modified mosquitoes cross over to other organisms? Can the genes from a genetically modified mosquito get into animals, including humans, or other insects?
The spread of genetic information that is inherited would occur if the Aedes aegypti species were to breed with another mosquito species; however, the Aedes aegypti mosquito is a distinct species which can not breed with other mosquito species.
The spread of genetic information that is not inherited (or horizontal transfer) was a serious consideration in each of the genetic strategy designs. Each strategy was designed to mitigate even the most remote possibility of this chance occurrence.
Question 13: Why is this research not being done in the USA?
For the work to have meaning it must be shown to be effective where it would be employed. To do the field experiments in the USA and not in the dengue virus endemic country would mean that the results may not apply to the conditions in the field.
Question 14: How will you get consent from the community at the test site?
Community engagement and consultation with local persons at candidate field sites as well as with persons responsible for regulating transgenic-insect research, will be combined with limited aspects of capacity-building to enable appropriate mechanisms of informed consent and community consent for field trials. The two-way process of community engagement is designed to enhance the local communities understanding of the scientific, cultural, and ethical aspects of the proposed research. Further considerations will be addressed regarding possible future options for disease control, and to also ensure that the control strategies have regard for local and national values.
Question 15: Who is responsible for GMO policy in each country?
This depends on the country. In the United States, several agencies are involved: The USDA Animal and Plant Health Inspection Service (APHIS) regulates the field-testing of genetically-engineered plants and certain microorganisms. The Department of Health and Human Service’s Food and Drug Administration (FDA) governs the safety and labeling of drugs and the nation’s food and feed supply, excluding meat and poultry. The Department of Health and Human Service’s National Institutes of Health oversees guidelines for the laboratory use of genetically-engineered organisms. The guidelines are generally voluntary, but are mandatory for any research conducted under federal grants. These are widely followed by academic and industrial scientists around the world and are part of this project.
A short list of agencies in the countries of some of the potential field sites of this study are: in Mexico, the Offices of the Secretary of Health, in Peru, the Peruvian Institute of Health and in Trinidad, the Ministry of Health and the Caribbean Health Research Council Ethics Committee, among others.
Question 16: What research is the project carrying out on risks of GMOs before they are released into cages?
The cage testing of all of the proposed population replacement and reduction experiments with GM mosquitoes will be done in three phases. The first two are in the laboratory and are designed to determine if the genetic modifications work as planned under small-scale controlled conditions. These phases will have to be successfully completed before the mosquitoes will be placed into the field cages.