New Delhi: Dengue is the most widespread mosquito-borne disease in the world, and is caused by dengue viruses, which is spread to people through the bite of an infected Aedes species (Aedes aegypti or Aedes albopictus). These mosquitoes also spread Zika, chikungunya, and other viruses, according to the Centers for Disease Control and Prevention (CDC). The transmission of dengue between humans is mediated by the bites of female Aedes aegypti mosquitoes.

About four billion people in the world live in areas with a risk of dengue. About 400 million people get infected with dengue each year. To date, there are no medical treatments for people suffering from this disease. 

The dengue virus causes symptoms ranging from high fevers to severe bleeding and shock, and can be life-threatening. Most common symptom of dengue is fever with nausea, vomiting, rash, or aches in the eyes, muscles, or joints. The disease presents an enormous burden on health systems. 

An international team of researchers has recently developed a mathematical model for the virus. The study was published on April 19 in Chaos: An Interdisciplinary Journal of Nonlinear Science. This is a journal by American Institute of Physics (AIP) Publishing. 

In 2009, scientists discovered that mosquitoes carrying Wolbachia bacteria lessen the chances for the dengue virus to affect humans.

However, mosquitoes do not acquire Wolbachia bacteria in their natural environment. The bacterium must be introduced in vitro in mosquitoes’ eggs, a statement issued by the American Institute of Physics said. The eggs are later released in areas affected by dengue transmission.

Wolbachia-Infected Mosquitoes Prevent Vector-Borne Diseases

Over the last decade, the release of Wolbachia-infected Aedes aegypti into the natural habitat of the mosquito species has become the most sustainable and long-lasting technique to prevent and control vector-borne diseases such as dengue, Zika, or chikungunya, the authors noted in the study. However, the limited resources to generate such mosquitoes and their effective distribution in areas dominated by the Aedes aegypti vector present a challenge for policymakers, according to the researchers. 

How Is The New Mathematical Model Beneficial?

Hence, the study authors have introduced a mathematical framework for the spread of dengue in which competition between wild and Wolbachia-infected mosquitoes, and other crucial factors have been combined. 

According to the study, the framework allows the researchers to identify the most effective areas for the release of Wolbachia-infected mosquitoes to achieve a large decrease in the global dengue prevalence.

Mosquitoes which have been infected with Wolbachia bacteria naturally take over the local mosquito population.

For the new study, the researchers used real data on human and vector activity, in order to understand the epidemiological situation. Epidemiology is the study of the distribution and determinants of health-related events, including disease. 

The researchers collected the data to identify the geographical areas with greatest vulnerability, creating a ranking of areas that prioritises those where Wolbachia-carrying mosquitoes can have the strongest and most beneficial impact on the spread of the dengue virus.

According to the statement, Jesus Gomez-Gardenes, who co-authored the study, said one might think that the most populated areas are those in which Wolbachia release would be most beneficial. However, this is not always true, he said.

The researchers observed that once they immunise the most vulnerable geographical area, the ranking of the remaining areas is affected. This gives rise to a new scenario that tells them where they should concentrate resources in the second instance and beyond, according to the study. 

The theoretical framework offers policymakers an alternative to effectively release Wolbachia-infected mosquitoes by identifying the most epidemiologically vulnerable areas. In this way, they can concentrate on the use of limited resources available for better control of dengue transmission, the authors noted in the study.

Significance Of The Study

The World Mosquito Program, which is currently releasing Wolbachia-infected mosquitoes to protect the global community from diseases such as dengue, chikungunya, yellow fever, and Zika, will find the results beneficial, the statement said.

Gomez-Gardenes said that data-driven models have also proven useful to tackle the evolution and mitigation of other diseases such as Covid-19. He hopes that the framework developed for dengue can be further generalised for tackling the control of other vector-borne diseases.

The use of mosquitoes infected with Wolbachia bacteria has emerged as a sustainable and long-lasting way to prevent and control dengue, because the bacterium nullifies the ability of mosquitoes to transmit the dengue virus.