Study shows dengue virus turns virulent under higher temperature

THIRUVANANTHAPURAM: A team of researchers at the Rajiv Gandhi Centre for Biotechnology (RGCB) here has found that dengue, a recurring tropical disease that witnesses an outbreak in the monsoon, becomes more severe and hostile in animal models when its virus (DENV) while being grown in mosquito-derived cells is exposed to higher environmental temperature.

The research, which can phenomenally help in predicting and mitigating the severity and virulence of dengue, has assumed critical importance as it seeks to establish the impact of global warming on the disease, with an estimated global disease burden of 390 million cases per year (WHO).

The study was recently published in The Federation of American Societies of Experimental Biology (FASEB) journal of America.

Dr Easwaran Sreekumar, who led the research team, said: "The body temperature of mosquitoes is not constant as in higher animals and it increases or decreases with the environmental temperature... So far it is not known whether the higher temperature growth condition will affect the virulence of the virus. For the first time, our recent study points that there is such a possibility. DENV cultured at a higher temperature in mosquito cells was significantly more virulent than the virus grown at a lower temperature."

Besides Sreekumar, other members of the research team included Ayan Modak, Srishti Rajkumar Mishra, Mansi Awasthi, Sreeja Sreedevi, Archana Sobha, Arya Aravind, and Krithiga Kuppusamy.

"In seasons of enhanced environmental temperature, with intermittent rainfalls promoting mosquito growth, there is a chance of emergence of more virulent dengue virus and severe disease conditions. In the dengue outbreaks happening in various parts of the country, this aspect has never been looked into. Our study alludes to the growing implications of global warming and its possible effects on infectious disease dynamics," the researchers added.

It was earlier observed that a relatively higher environmental temperature shortens the incubation period of the virus in mosquitoes, resulting in an increase in human transmission.

RGCB Director Prof Chandrabhas Narayana said that the researchers have been making efforts to understand why dengue becomes serious at times. "But even after decades of research, there are still no effective vaccines or antivirals to control or prevent the recurring disease. This study has major implications in predicting severity of dengue outbreaks."

The study was conducted in a mouse model, where the virulent strain obtained from the higher temperature growth caused enhanced presence of viruses in the blood, hemorrhage, severe tissue changes in vital organs such as heart, liver, and kidney, which are the hallmarks of the disease, and even death.

Dengue is a viral infection caused by DENV and transmitted to humans through the bite of infected mosquitoes.

Globally, the incidence of dengue is on the rise over the years, with a corresponding increase in the disease severity and fatality. While in majority of the patients, the disease is mild and self-limiting; in some patients, it causes life-threatening thrombocytopenia (extremely low platelet count in blood) and shock syndrome.