By Glenn Petrie, Ph.D.
Senior Scientific Advisor
ABC Laboratories
Senior Scientific Advisor
ABC Laboratories
www.abclabs.com
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.