Friday, January 29, 2016

Zika crisis - danger and opportunity

Aedes Aegyptiae mosquito

Zika virus is causing a lot of justifiable concern right now. It is reasonable to call it a crisis.

Crisis means danger and opportunity.

The danger is that it can cause a huge number of people with microcephaly mainly in tropical regions, but it also presenjts us with the opportunity to eradicate the mosquito that carries it.

The virus was first identified in 1947, as the cause of a mild flu-like illness, often with a rash, but it has recently been associated with a birth defect - microcephaly, or small brain - in women who get Zika in the first 3 months of pregnancy. It is also linked with a high number of cases of Guillian-Barre syndrome, where weeks of near-paralysis follow a virus infection.

Initially the virus was limited to tropical Africa, but has recently spread rapidly to many countries that host the Aedes aegyptii  mosquito. Note that this is different species from the Anopheles that carries malaria.

Two factors lie behind this explosion of Zika - air travel, and climate change. The warming global climate will inevitably increase the mosquito habitat. It is possible that the virus has mutated.

This map shows the countries which are vulnerable to Aedes mosquito, and therefore to Zika virus.

Note that Florida and the South Eastern USA are potentially affected. This changes everything. The disease is not there yet, but it is only a matter of time, and when it arrives it will motivate the US Government to do something to neutralise the mosquito threat.

Note also that it threatens the success of the Brazil Olympics. Any woman (and her partner) who is pregnant, or contemplating pregnancy, should stay away as things stand now.

These factors will push for a quick solution to the problem.

There are two approaches on offer: attack the virus, or attack the mosquito that spreads it.

Attack the virus? A vaccine will take a year or so to develop, and there are no antiviral treatments (except one success with the impossibly expensive interferon).

So we are left with the anti-mosquito approach, which is much more promising and interesting.

We know a lot about mosquito control, because they carry no less than 16 diseases: not just malaria (which causes 200 million cases a year and 440,000 deaths) but also 

  • dengue fever
  • yellow fever
  • West Nile virus
  • Saint Louis encephalitis virus
  • Eastern equine encephalomyelitis virus
  • Everglades virus
  • Highlands J virus
  • La Crosse Encephalitis 
  • Ilheus virus
  • filariasis (elephantiasis)
  • Rift Valley fever
  • Wuchereria bancroft
  • Japanese Encephalitis
  • chikungunya
  • Murray Valley encephalitis

    That it one hell of a lot of illness, suffering, grief, burden on health services and economic loss.

  • Why do we put up with it?

    Maybe because up to now the mosquito has been a pest that affects poor tropical countries. 

    Rich visitors can cope by taking measures (see below), so it tends to get ignored.

    We now have an opportunity to mobilise public opinion, motivate politicians and control, or even eradicate, the mosquito.

    Mosquito Control
    Control starts with the personal.
    In areas with mosquito-borne disease, 
    • take anti-malarials (I personally know of the case of a young couple who died of malaria because they refused to take "Western Medicines")
    • use mosquito nets soaked in insecticide
    • apply insect repellent if outside of the net, especially at dawn and dusk (though the Zika virus can be transmitted during the day too).
    • keep the house clear of mosquitoes with screens and insecticide .

    Outside fumigation with insecticide is dubious, because it kills beneficial insects and raises the chance of resistance developing.

    Mosquito traps  may have a role.

    The main attack outside the house is more interesting: denial of habitat. 
    This is great, because it is low-tech, creates work, and is aesthetically pleasing.

    The aim is to eradicate any pools of standing water. This means
    • modernising open sewers
    • draining or filling puddles
    • tidying up litter (water can pool in any concave surface in discarded plastic, tyres etc)
    • clearing and filling nooks and crannies
    • more here
    This means that Rio and other Olympic cities should be clean and tidy, sparkling for its visitors in August, and the population will be pleased because they will all have been in work and therefore less poor. The abolition of open sewers would be a huge step forward from every point of view - aesthetic, medical, economic, political.

    Marshes and other watery areas can be managed. Bio-control involves introducing fish or other things that eat mosquito larvae, but this can be ecologically disruptive.

    All of this denial of habitat will create a huge number of jobs, so is a boon to the poor and the unemployed. Because there is such a good return on investment, funding should not be a cause of delay.

    There is even a case to be made for governments to create the money needed to pay for the work directly. Money is created mainly by banks through debt, but governments give them the power to do this, and therefore governments also have the power to create money directly, and this is a very reasonable thing to do if it brings future savings of expenditure, and is good for the health of the people, which is after all, the purpose of government.

    Last but not least, we have a promising new treatment - release of sterile male mosquitoes.

    Oxitec is an Oxford based company which is producing millions of genetically modified male mosquitoes. These can mate with female mosquitoes, producing young which die before they can reproduce. The product has been approved and trialled and is already in use in Brazil.

    Some may be surprised that a Green blogger and activist is backing this GM technique. The point here is that the technique is for the good of humanity, that the GMOs we are talking about here are intrinsically not self replicating beyond their own immediate progeny. Greens are not against genetic modification per se, but because of  specific problems arising from some applications. 

    The GM approach, combined with the other measures mentioned above, should be able to reduce or even eliminate the threat by the time of the Olympics if everyone concerned including the politicians does their work efficiently.

    Assuming we win a famous victory over the virus for the Olympics, we will have a model that can be rolled out in the rest of the world. If pursued to the end, we could eliminate the mosquito from the face of the planet.

    Would it matter if the mosquito were driven to extinction? They do provide food for birds, insects and bats, but they are not wholly reliant on them, and even the mosquito fish can live on other larvae.

    It is possible if not probable that another insect will move into the niche, but we can inspect that situation when it arises. It is unlikely that it will be worse than the mosquito.

    Here is an article in Nature about the effects of mosquito extinction. It suggests the worst outcome would be - an increase in the human population.

    There may be unknown effects from mosquito eradication, but it would be unreasonable to oppose eradication of a known major problem on grounds of some future unspecified possibility.

    Over the next few months, we need to have a big debate about whether we want to make some or all species of mosquito extinct. The question has been raised by Dr Olivia Judson here.

    So, in summary:
    • Zika is a major problem
    • It can be contained by attacking the mosquito population
    • A combination of low tech job-creation and high tech GM techniques can beat the problem, given the political will


    David Flint said...

    An excellent approach Richard. I have no problem backing the release of male GM mosquitoes as part of a wider strategy. It provides a quick hot whilst we mobilise for the habitat denial work.

    I'm much less happy about eliminating a species. I'd want to see lots of research and trials before saying yes.

    DocRichard said...

    Hello David, nice to see you here. I am studying (slowly, with a wet towel wrapped around my head) the question of whether the transposon used in creating the GM mosquito is incapable of affecting the virus itself. Oliver Tickell is worried. I think more research is needed.

    As to elimination, best to kick that into the long grass at present, as it is an emotive subject. The main job at the moment is to push Aedes etc away from humans, and reduce mosquito numbers.

    I was going to say you can't do a trial of elimination, because it is all or nothing. But you could do a trial on an island. And if for some reason they are missed - well, nothing would be easier than to re-introduce the little bastards.