Mathematicians Use Computer Simulations to Plot Reduction in Zika Vector Population

As the number of locally-acquired Zika cases rises in Florida, mathematicians are researching a new approach to control vector populations.

The Zika-spreading vector, the Aedes aegypti mosquito, is also known to spread other viruses, such as chikungunya, dengue, and yellow fever. According to a press release, Mac Hyman, PhD, mathematics professor at Tulane University, is collaborating with other scientists in a study funded by the National Science Foundation (NSF) in an effort to devise a plan that will outline a path to fight Ae. aegypti mosquitos with bacteria. His team aims to use Wolbachia bacteria to reduce Zika-vector prevalence.

Previously, Wolbachia was found to block Zika virus transmission in Ae. aegypti mosquitoes. According to Hyman, “The idea is to create a Wolbachia epidemic in A. aegypti mosquitoes so they are less capable of transmitting the virus. Wolbachia already occurs naturally in 25-75 percent of the insect population, but not in A. aegypti. Infecting the mosquitoes with [these] bacteria can reduce their ability to lay viable eggs and shorten their lifespan by a day or two.”

However, this approach may be more complicated than initially perceived. According to the mathematician, if only a small number of Wolbachia-infected mosquitos are introduced into the population, these bacteria-infected mosquitos would essentially be ‘quickly wiped out’. According to Hyman’s research, at least 40% of a vector population needs to be infected with the bacteria in order to “establish a ‘threshold condition’ where the bacteria could take hold in the wider population.”

In an attempt to learn how to overcome this obstacle, Hyman and Ling Xue, PhD, postdoc researcher at Tulane University, created a computer-simulated virtual world where they tested several approaches to sustain the Wolbachia-infected Ae. aegypti population. According to Hyman, they found that they needed to wipe out all Zika-infected mosquitos, larvae, and eggs, before they were able to introduce and sustain the new bacteria-infected vector within the simulation. He noted that, looking back, this approach seems obvious. By using a computer-simulated virtual world, the scientists were able to take more of a trial and error approach to their research, without the cost of a real-world test.

Meanwhile, active Zika transmission has been confirmed in the United States in Miami-Dade County by both the Florida Department of Health (DOH) as well as the CDC. Today, the Florida DOH confirmed that the number of locally-acquired Zika cases has risen from 17 lab-confirmed cases identified, to 22 cases. In addition, Puerto Rico reported its second Zika-related death on Monday.

Given that the Zika virus is known to cause microcephaly and other neurological impairments in fetuses of infected pregnant women, as well as Guillain-Barré syndrome (GBS) in adults, it is imperative that we find a way to combat the virus, and studies, such as Hyman's are bringing us one step closer to reaching this goal.