By Glenn Petrie, Ph.D.
Senior Scientific Advisor
Senior Scientific Advisor
Zika is a disease caused by the Zika virus which is spread to humans primarily through the bite of an infected Aedes species mosquito. The disease can also be by transmitted through sex with an infected partner. The symptoms of Zika are fever, rash, joint pain, and conjunctivitis. The illness is usually mild with symptoms lasting for several days to a week and rarely requires hospitalization. There is no vaccine or specific treatment for Zika virus infection. Treatment is symptomatic and supportive, including rest and the use of acetaminophen to relieve fever.
Federal health officials recently confirmed that the Zika virus causes a rare birth defect and other severe fetal abnormalities, typically, abnormally small heads and severe brain defects. There is also limited evidence of Guillian-Barre’ syndrome and multiple sclerosis being related to Zika infection. The greatest risk is to pregnant women; however the Center for Disease control has recommended that men and women should wait a minimum of 8 weeks after possible exposure before trying to conceive. This period may increase based on the latest findings regarding the latency of the virus.
In a recent article in The New England Journal of Medicine it was noted that Zika is the fourth mosquito-borne illness to infiltrate the Western Hemisphere over the past 20 years, following dengue, West Nile, and chikungunya. There is currently no available vaccines for any of these diseases. According to the World Health Organization (WHO), more than 60 research institutes and companies are working on products to combat the spread of the Zika virus, but a vaccine is likely to take years to develop.
The disease can alternatively be attacked by control of the vector, Aedes aegypti. WHO states that traditional insecticide spraying methods have had no significant impact in decreasing the spread of dengue, implying that these classical methods for battling mosquito borne disease may be equally ineffective for Zika.
There is another possibility for eradicating the Aedes species mosquito over large areas. This involves modification of the mosquitos themselves. This approach has been used successfully in the past for eradication of the screwworm, an insect that was a major cause for livestock deaths in the mid- 20th century. The screwworms were irradiated, sterilizing the male flies. Only the male flies were released, typically sprayed from small planes. The sterile males could not produce progeny, gradually eradicating the species. The technique was an unmitigated success. The last cases of screwworm in the United States were reported in 1982, followed by eradication in Mexico and Central America.
Now, the world is focused not only on the Zika virus, but dengue, chikungunya and yellow fever, all transmitted by Aedes aegypti . A British company, Oxitec, has approached the problem utilizing genetic engineering and inserting a gene that kills the insect. Male mosquitoes containing the gene are released to mate with wild females. The released male mosquitoes have no effect on people because males don’t bite. Offspring die before they reach adulthood, in that way suppressing the population of wild mosquitoes. Small-scale tests conducted in the Cayman Islands, Panama and Brazil since 2009 reduced local mosquito populations by as much as 99 percent.
Last month the federal government tentatively approved a field test (Florida Keys) of genetically engineered mosquitoes that might help slow the spread of the Zika virus. A final approval for the trial will not be made until the FDA receives and assesses comments from the public, which is likely to take months and the plan has faced fierce opposition from some residents in the state.