Blackflies are carriers of a worm causing river blindness.
| Photo Credit: SPECIAL ARRANGEMENT
A new study involving DNA barcoding to identify species accurately is expected to lead to better management and control strategies for blackflies, which are carriers of a worm causing river blindness.
The findings by a team from the Diptera division of the Zoological Survey of India (ZSI) were published in Vector-Borne and Zoonotic Diseases, a leading international research journal. The authors of the study are Arka Mukherjee, Oishik Kar, Koustav Mukherjee, Bindarika Mukherjee, Atanu Naskar, and Dhriti Banerjee.
River blindness is a parasitic disease caused by the worm Onchocerca volvulus, transmitted through the bites of infected blackflies that breed near fast-flowing rivers, leading to skin problems and potential blindness.
River blindness follows trachoma as the leading cause of infection-related blindness worldwide. The World Health Organisation (WHO) considers river blindness or onchocerciasis among the most neglected tropical diseases.
The ZSI team collected blackflies or Simuliidae from eight distinct central Himalayan locations around Kalimpong and Darjeeling in West Bengal. These blackflies are locally called pipsa or potu.
A recent world inventory lists 2,424 species of Simuliidae, of which at least 27 species or species complexes are known to transmit Onchocerca volvulus, the causative agent of the disease in humans.
The researchers said the first step in protecting people from this disease was to properly identify and control the vector — the blackfly. Better identification of the disease carrier was thus deemed essential for improved treatment.
“Blackflies of the Simuliidae family are extremely small, barely noticeable to the naked eye. Before one realises it, the fly has already sucked blood and departed. Many species in this family look almost identical externally,” Dr. Banerjee, also the director of ZSI, said.
“In scientific terms, distinguishing between two different species of Simuliidae flies based on external characteristics is quite difficult and time-consuming. Sometimes accurate species identification is not even possible,” she said.
For this reason, the researchers used DNA from four species of blackflies — Simulium dentatum, Simulium digitatum, Simulium praelargum, and Simulium senile — as a means of identification.
“DNA barcoding methods were used to identify the species after preliminary segregation based on external characteristics,” said Dr. Naskar, the officer in-charge and scientist at ZSI’s Diptera division.
The DNA was barcoded after collection from the legs of the blackfly samples. Specific gene sequences were used to distinguish the four species of blackflies as potential vectors.
“Although locals are more vulnerable to these flies, the risk of blindness remains a concern for visitors who frequent places such as Darjeeling and Kalimpong,” Dr. Banerjee said.
Published – April 04, 2025 11:11 pm IST
