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Science is Helping Fight the Zika Virus (and the “deadliest animal in the world”)

Brazil is on the front lines of the mosquito-borne Zika virus epidemic. Last May saw the first confirmed case of Zika in Brazil. Now millions are believed to be infected in Brazil and the virus has spread to 22 other countries and territories. With the evidence suggesting that the virus could also cause a devastating birth defect, the World Health Organization (WHO) declared the outbreak in the Americas a public health emergency.

WHO claims that the pathogen, which was virtually unheard of in the region a year ago, is spreading so fast that it could infect as many as 3 million to 4 million people within 12 months.

The virus is now making the headlines on every major channel.  Airlines are refunding fares to reluctant travelers, while efforts to develop a vaccine are underway. There’s even talk about the need to cancel the 2016 Olympics in Rio.

The Cause

Zika is spread by the Aedes aegypti mosquito, which is also known to transmit diseases such as Dengue, yellow fever, and Chikungunya. Key to dealing with the Zika epidemic will be tracking and forecasting the spread of the mosquito population, and then getting rid of the pests.

Eliminating the Carrier

When I started investigating how science is aiding in the battle against the Aedes aegypti mosquito, I frequently encountered the term “vector management”.  So off to Wikipedia, which succinctly explains:

“In epidemiology, a vector is any agent (person, animal, or microorganism) that carries and transmits an infectious pathogen into another living organism.”

Many municipalities have vector management systems in place, in which they aim to reduce the population of the “vectors” through reducing the habitat (standing water) and applying pesticides. The problem with the Zika mosquito is that large, area-based spraying may prove less effective, since these mosquitoes prefer to inhabit indoor spaces, such as closets and under beds.

Right now, a myriad of approaches are being used to prevent Zika, from emptying standing water to wearing long sleeves and using insect repellent.  But as long as the carrier mosquitoes remain, so does the risk. Carlos Marcondes, an entomologist who studies disease-carrying insects at the Federal University of Santa Catarina in Brazil, shared his advice for stopping the epidemic: “Preventing breeding is the only way.”

There are two main ways that preventative breeding can be effective,  by either eliminating the population or changing the population so that it cannot carry the virus.

Researchers (with MATLAB) Taking Aim at the Aedes Aegypti Mosquito

Brazil is trying an approach to cut wild mosquito populations by genetically engineering and releasing mosquitoes that can’t reproduce. Scientists reduce the populations of virus-carrying mosquitoes by introducing male mosquitos into existing population that cause the next generation to die before reaching maturity.  The reason male mosquitoes are used is simple: male mosquitos don’t bite and therefore cannot further spread the disease.

Combined with other measures, this could be key to stopping the epidemic. Looking to science, there is much work being done on this issue:

  • Optimization of the Aedes aegypti Control Strategies for Integrated Vector Management, by Marat Rafikov, Elvira Rafikova, and Hyun Mo Yang, looked at three techniques of mosquito population management, chemical insecticide control, sterile insect technique control, and environmental carrying capacity reduction. The goal was to obtain the most sustainable strategy to reduce the mosquito population. MATLAB was used to simulate a control problem where the main goal is to minimize the fertile female mosquito population.

Another approach that has shown promising results is intentionally infecting male mosquitoes with a bacteria called Wolbachia. Wolbachia is found in in most insects, but not mosquitoes. When it is injected into mosquitoes, it prevents them from becoming infected with viruses such as the Dengue, Chikungunya, and Zika arboviruses.

  • In the study Extreme Divergence of Wolbachia Tropism for the Stem-Cell-Niche in the Drosophila Testis by Michelle E. Toomey, Horacio M. Frydman, the authors state, “Because Wolbachia promote insect resistance against human diseases transmitted by mosquitos, Wolbachia are becoming a valuable tool in the control of several diseases, including Dengue and malaria.” This study uses MATLAB for image processing for density determination.
  • Another study, New insight into Wolbachia epidemiology: its varying incidence during the host life cycle can alter bacteria spread by P. Martínez-Rodríguez, R. Granero-Belinchón, F. Arroyo-Yebras, and J.L. Bella, used MATLAB to simulate the transmission of Wolbachia through 4000 generations after introduction.

So going back to the title of this post, How Science is Helping Fight the Zika Virus (and the “deadliest animal in the world”),
you’ve probably guessed by now that mosquitoes truly are the deadliest animal in the world.  According to the Gates Foundation, sharks kill fewer than a dozen people per year, but mosquitoes kill over 725,000. If you listen to the TED Talk by Bill Gates from 2009, you will hear him call for action from communicators, governments and scientists.  Finding ways to eliminate mosquitoes remains a critical issue across the globe (ok, except for Antarctica and Iceland!), and the Zika virus will bring even more attention to the efforts in the next years.

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