The epidemic has killed some 50 people and hundreds have fallen ill in the past few weeks, and authorities are fighting to control the further spread of the disease. In their effort, health officials are using guppy and gambusia fish that feed on mosquito larvae and are often used in mosquito control.

Thousands of guppies - the small, brightly coloured live-bearing freshwater fish popular in home aquariums - have been released in ponds, lakes, wells and dirty stagnant water bodies - places where mosquitoes breed.

"Guppies eat mosquito larvae and help check the breeding rate of mosquitoes," said Prabhakar Chatterjee, West Bengal's medical services chief.

Dengue, which is transmitted through mosquito bites, is marked by high fever, headache, rash and nausea, and if not treated timely can lead to death. Health volunteers, medical students and voluntary organisations are distributing the fish to be released in water bodies in the countryside.

"Gambusia is a cheap and an easily available fish that can eat daily its own weight in mosquito larvae or pupae," said Amiya Hati, an expert in mosquito-borne diseases. Using gambusia fish is encouraged because mosquitoes have become resistant to many of chemicals like DDT.

WB: 'Dengue outbreak not an epidemic'