Sunday, January 31, 2016

Economic opportunities in responding to the Zika Virus threat

The WHO is deeply concerned about the rapidly evolving Zika Virus (ZIKV) situation for 4 main reasons:
  • the possible association of infection with birth malformations and neurological syndromes
  • the potential for further international spread given the wide geographical distribution of the mosquito vector
  • the lack of population immunity in newly affected areas
  • and the absence of vaccines, specific treatments, and rapid diagnostic tests

The situation is urgent not just because of the immediate medical threat, but also a threat to the economy of Brazil. If fear of ZIKV deters people from attending the Olympics, scheduled for August 2016, this could negatively impact the economy of Brazil, which is already in a downturn. If Brazil goes into full recession as a result of a disappointing Olympics, this would be a factor pushing the global economy into recession.

For these reasons it it vital that the threat from ZIKV be neutralised.

There are two main lines of defence:

Measures against the virus
There are no antivirals available against the ZIKV at present.
A vaccine may take about a year to come on line - though Indian researchers are claiming they have a vaccine already (Feb1).
Medical research and technology will go ahead, and will no doubt be productive, but not in a time frame that can affect the situation in August 2016.

Measures against the vector
There are a range of measures that we can take against the mosquito that carries the virus, Aedes Aegyptii.

At the high tech end, the UK firm Oxitec have been releasing millions of Aedes male mosquitoes which are genetically modified so that 97% of their progeny do not reach adulthood. This technique has produced promising results in the Cayman Islands, Malaysia and Brazil, with reductions in mosquito numbers of around 90% reported.

However, it was found that in the presence of tetracyclines, (which are plentifully available in agricultural effluent) up to 15% of the progeny may reach adulthood. The effects of this have been studied, and the conclusion is that the levels of tetracycline in the environment where Aedes Aegyptiae likes to lay its eggs are not high enough to affect the Oxitec process.

There are fears that the operative bit of the genetic engineering, the transposon element, may affect the virus itself. However, the transposon is designed to work on DNA, and will not affect the virus, which works on RNA. 

Also there are suggestions in social media that since the microcephaly problem emerged in the same place as an Oxitec roll out of GM mosquitoes, the GM may in some way have caused the microcephaly. In fact the epicentre of the outbreak is many kilometers from the place where GM mosquitoes were released .

Although the fear that the GM caused the outbreak are without evidential foundation, it may well have an effect on the popular view of the GM solution, and cooperation with the authorities.

Whether or not GM methods are used to control mosquito populations, there is still a need for more conventional defences.

Pesticides do have a place in the system of defence. The best application is in pesticide-impregnated mosquito nets. These are very precise; they kill female mosquitoes that are seeking blood, attracted by the CO2 and odours emitted by humans. Next comes indoor spraying, onto walls and in closets and dark spaces, which are preferred nurseries for Aedes Aegyptiae.

At the other end of the scale of acceptability is general outside fumigation with pesticide. This may have a place in extreme scenarios, but the approach is inefficient and harmful to the health of humans and beneficial insects. Pesticides have a limited working life as resistance is inevitable, and the more they are used, the quicker resistance will develop. [updated]

Mosquito Habitat Source Reduction (SR) is the classical and proven defence against mosquitoes. It means removing their habitat – stagnant water – as far as is reasonably practical. This means emptying any potential of water – litter, tyres, containers gutters, puddles, hollow trees and especially open sewers.

The task is simple. Accomplishing the task, and making a permanent habit of it is extremely challenging, but not impossible.

A successful source reduction programme would look something like this:

Each neighbourhood would have one or more Source Reduction Officer (SRO) appointed.
This would be a paid post.
The officers would be chosen from the neighbourhood.
They would be trained to know why SR is so important, and able to pass on their knowledge to their neighbours.
People would be expected to cleanse their own properties voluntarily, but work carried out in common areas should be paid for.
Anyone in receipt of state benefits would be paid for their work in addition to their benefits. Neighbourhoods would be inspected periodically from outside, incentivised by rewards and compliments for success, and in the event of failure, the SRO may be replaced.

Favellas and other poor communities would need additional help in setting up their programme.

The programme of sewer modernisation would provide a significant economic stimulus, which is particularly welcome in a recession.

Politicians and economists must see the SR programme as the excellent investment that it is.
Lack of money must not be offered as an excuse for inaction.

In addition to SR, the Government will make sure that every citizen has access to pesticide impregnated mosquito nets, screens and any other relevant materials and knowledge.

The rewards of success of this programme are as follows

  1. Comfort and amenity for all
  2. Costs of disease avoided
  3. Costs of disability (microcephaly) avoided
  4. Demand reduction on local health services
  5. Employers would find that sick leave is less.
  6. Work opportunities for Brazil's 7% unemployed, with reduction in income inequality in the country.
  7. Improved visual amenity as litter disappears, which would boost tourism.
  8. General morale will benefit as people get the satisfaction of realising that they themselves have helped to defeat the mosquito and the disease it causes.
  9. This sense of empowerment may encourage formation of similar programmes.
  10. Roll-out of successful programmes can provide an effective model for other mosquito-affected countries.

The challenge of ZV gives us an opportunity of transforming community life economically and in other ways by engaging ordinary people in the fight against disease.

Dr Richard Lawson MB BS, MRCPsych

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