Zika virus infection 2015-16 Epidemic
April 12, 2016 Update
Paul Herscu ND, MPH
Herscu Laboratory
The Time is NOW for Some
Mosquitoes to Go
This article deals with only one aspect of prevention of
Zika virus caused disease, and is the fourth of a series. For previous writings
on the subject and to contextualize this writing, see: http://www.paulherscuepidemics.blogspot.com/
When my older son was entering middle school, he and I
attended several Bioblitz events, which are 24-hour inventories of all species
in a certain area. We got into the concept, after he read a book written by
E.O. Wilson, Consilience. He later met Dr. Wilson, exchanged
correspondence, joined the Explorer's Club and eventually gave lectures on the
concept of the bioblitz. He also had the idea of connecting the E.O. Wilson's Encyclopedia
of Life (http://eol.org) project with the Bioblitz
events that occur in the National Parks of the USA. If you want to read about
how the Bioblitz concept began, please see this link:
The reason I highlight this concept is to say that my family
is and has always been very environmentally friendly. We have worked for and
continue to work towards a stable, robust biodiversity, not only for trophy,
keystone, or umbrella species, but for all species. Diversity is essential for
our own species to survive and thrive.
That said, and as an environmentalist, I believe the time
has arrived for us, as a species, to drive into functional extinction a few mosquito species or species groups. The
reasons are compelling, rational, ethical, and scientific. I would like to
place this topic in context.
First, I am not suggesting we attempt to get rid of all or even most mosquito species, only a few which act as vectors of diseases that haunt humanity, and represent less than 1% of mosquito species. The best, or most troubling example of this is the Anopheles gambiae group, which is a collection of several very similar mosquitoes that are the primary vectors of malaria. There are perhaps 40 subspecies of Anopheles that carry the Plasmodium falciparum parasite, which is primarily responsible for malaria. In other words, more than half a million men, women, and children die annually of malaria in sub-Saharan Africa because of bites from these mosquitoes. It is often said that half of all people who have ever lived died due to the mosquito being the vector of disease. That is a huge impact! This may seem abstract for people, but if you come from or travel to an area impacted by malaria, it becomes very clear, very quickly the price our species pays because of malaria.
For a closer example of another mosquito, we have the Aedes aegypti species that likely
carries Yellow fever, Dengue fever, Chikungunya, and Zika virus, leading to
many thousands of human deaths per year, let alone all the many millions of
infections and hospitalizations.
A single species of mosquito makes many individuals ill
and is more dangerous to our species than most things we worry about like seat
belts, food additives, non-organic foods, gun violence, or any other threatening species. Yes, these are all
important, but nothing comes close to the misery that a few species of
mosquitoes cause humanity. It may be that the reader has felt immune from these
issues, because of where they live, but the problem is very real.
There are well over 3,000 mosquito species, with only a
small handful being vectors for human disease or diseases of animals important
to us. I am suggesting leaving over 99% of those species alone and only
addressing the main species that harm us.
Here is an ethical argument. By not acting, we let many millions of people die of malaria. In fact
from the time I finish writing this short essay until the time it is published,
thousands of people will die from malaria. Which is not to say that a great
many other interventions are not occurring or working. But even with these effective interventions,
we still have so much preventable morbidity & mortality; half a million
people will still die this year.
Here is another ethical argument, for the mosquito's
sake. People kill mosquitoes in most cultures around the world. We swat at
those that land on our bodies, realizing that they are going to bite us; action
and reaction. However, in many cultures, we also fumigate areas to kill all surrounding mosquitoes, even ones
that do not interact with humans. This is done inside the house, but also a
great deal outside the home, with high, low, or ultra-low volume (ULV)
applications (spraying) of neighborhoods, from trucks, cars, and planes. Given
that we do this, currently, around the world, we are killing many, many
millions of mosquitoes belonging to species that are not vectors of human
disease, killing ones that do not even bite us. I have an ethical problem with
this, as we are killing living beings that are not a problem for us. This means
that there is an ethical argument to change the current status quo. Help me
save 99% of the mosquitoes out there.
In every calculation, these few species of mosquitoes are
not modeled to be missed from the web of life. In other words, since we are not
getting rid of all mosquitoes, there will be no large crash of a food web. Bats
will continue to eat; pollination will continue to take place. I began this
writing by saying functional
extinction. By which I mean we can keep remaining mosquitoes of those species
in closed quarters. This means that for the rest of the world, the species is
missing, yet it is still in a lab, much as smallpox exists in a lab but not in
the outside world. Then if and when we ever want to release them again, we can.
I have a hypothesis about time sensitivity. Early on, the
viruses are carried by one vector. If we let the viruses spread without
specifically addressing their life cycle, an ever-increasing number of species
will act as vectors carrying these viruses. This seems to have been a pattern
of spread through the web of life. This is my way of saying that the very best
time to stop the spread of these illnesses is now! Time works against us in this
instance. We have seen this already in the migration of Zika virus from one
mosquito in Asia to another one in the Americas.
Also relevant is the vaccine challenge. Sooner or later
we will have to address a simple reality around the current vaccine concept, so
let's do it now. When we thought that there was just one infectious agent that
we had to vaccinate against, things theoretically worked out well enough. Then
the one infectious agent and one vaccine became 2, 5, 10 different agents
requiring ten different vaccines. Consider the following trajectory. We are
very early on in our ability to identify which viruses and bacteria exist and
how they impact us. In other words, there is an ever-increasing list of viruses
and bacteria that we are discovering that cause disease, and potentially,
epidemics. If we continue at the current rate of infector discovery followed by
the creation of a vaccine, and adding that vaccine to our vaccine programs, we
are going to end up with hundreds of vaccines for each of us. Sooner or later
this approach is unsustainable, both practically and economically. While it may
not seem obvious now, soon we are going to have to rethink the vaccine concept.
I am not even addressing here efficacy failures, such as the annual influenza
vaccine that often fails, or other issues associated with vaccines. Simply put
the general population, including the medical profession is going to have to
develop a different method of protecting the general population, different from
species-specific vaccines we have now. More on this exciting topic another
time.
The point I am making here is a simple one: there is one
mosquito species, the Aedes aegypti species,
that may well be carrying Yellow fever, Dengue fever, Chikungunya, or Zika
virus. It is conceivable that removing one mosquito species may mean that we
may have to give 4 less vaccines (once they are fully developed). An added
benefit is that we would not have to contend with issues of efficacy or adverse
events of any one vaccine. The public relation mess of the Lyme Disease Vaccine
LYMERix is a case in point. And whether it caused adverse effects in reality,
and whether it protected a greater number than 78% of those vaccinated is not
the issue, as much as a complete mess that this caused and had to be withdrawn
from the marketplace. We could skip all these headaches if the vector carrying
these bugs did not exist, and thereby making it less likely for humans to be
exposed to these viruses.
The how to. Sadly, or fortunately, our species has gotten
increasingly more efficient at driving other species to extinction. We now have
a mechanism that can do this fairly well, relatively cheaply, and without
harming the environment, in a targeted fashion against a species that is
harming us, as conceived by Raymond Bushland and Edward Knipling (https://www.worldfoodprize.org/en/laureates/19871999_laureates/1992_knipling_and_bushland/).
One main problem is that it is really misunderstood and conflagrated with other
similar sounding mechanisms that are truly toxic to the environment and for our
species. And here, before understanding the full enormity of human suffering, I
think people are going to raise incredible objections to, confusing this with
very real issues of GM food. Here I speak of Sterile Insect Technique (SIT).
The concept is a pretty simple one. Release many, many sterile male mosquitoes
such that there is no next generation after mating. A related method RIDL
(Release of Insects Carrying Dominant Lethal) where the males have been
genetically modified such that when they mate with a female, the next
generation does not survive (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062711). These groups of males outcompete the wild type
counterparts, making there be a smaller next generation and thereby the
population diminishes. Repeating this process several times, you can imagine
how the population would decline. The strength of this sort of program is that
it is species specific, not harming food or other species, sidestepping
fumigation and the toxicity it brings, halting larvicidal sprays and
applications and the potential harm they bring to all mosquitoes, even the ones
that do not harm us.
To most of us this seems both inhuman behavior and not
likely to work. However, a closer look at our history shows that we have
already used these approaches. Medfly in Chile, Screwworm fly in the USA, or
the Tsetse fly in Zanzibar have all been dealt with using one of these
techniques. We have saved lives, limited disease, and gotten rid of a fly that
was decimating the livestock in the southern USA and Mexico. I highlight only a
few examples of this approach, even malaria being a work in progress.
And I know these biological strategies seem complex and
confusing. In fact, we are at the point that some people actually think that
Zika virus has spread in Brazil because of this strategy being used this past
year. They may not fully understand the biological strategy fully, or the life
cycle of mosquitoes, as for example thinking that these modified males are
biting people and spreading the disease, not realizing that males do not bite
people.
In summation, every single year there are hundreds of
thousands of people dying and many millions of others becoming gravely ill from
illnesses that are preventable by getting rid of a few species of mosquitoes.
It does not seem that these few species add much to the web of life, yet cause
us a great deal of misery, in morbidity and mortality as well as national
economic hardships depriving survivors of a stable future.
Back to my introduction. What might be surprising, or
enlightening, is that many of the most prominent entomologists, biologists, and
environmentalists, have taken the same position. Here I would give as an
example E.O. Wilson, who helped coin the term biodiversity, who's love of
insects is not just infectious but has raised to our awareness the full import
that insects play within the web of life. He would like to see these particular
species of mosquitoes gone. All you have to do is take a proper appraisal of
the human misery such illnesses produce to arrive at this conclusion.
If you have concerns about biodiversity, pick a species
that we already know provides benefits to the environment and to people. I am
sure there is a species near you that needs help. But if you would like to pick
mammals nearing extinction you can pick a project such as the one attempting to
double the number of wild tigers, for the benefit of the species, of people,
and as an umbrella species for the region.
For equal time and full disclosure. Zika virus is coming
to the USA. One of the main ways to contend with this Zika virus is to contend
with the mosquitoes. The FDA is currently evaluating safety and efficacy of one
such process. If allowed, at least one company will be releasing these types of
mosquitoes in the USA as a way to reduce the population of the species. If you
have any comments or concerns about the technology, pro or con, consider
writing the FDA by following the link:
