Authorities battling virus claim to have turned tide against mosquitoes that carry disease with help of 1.6m fish

This article is more than 6 years old

This article is more than 6 years old

On one side of the battle are the countless swarms of mosquitoes that thrive in Pakistan's steamy summer months. On the other, vast quantities of hungry fish conscripted into a fight against a deadly virus that is reaching epidemic proportions.

Authorities battling the menace of Dengue virus claim to have turned the tide against the mosquitoes that carry the disease with the help of 1.6m fish released this year into pools, puddles, fountains and any other potential insect breeding places they can find.

Punjab has waged an all-out campaign against Dengue – a potentially lethal disease spread by mosquito bites – since a major outbreak in 2011 infected tens of thousands and killed more than 300 people.

Software designers were tasked to make smartphone apps to track outbreaks, the government cracked down hard on anyone who left old tires in areas where they could collect rainwater, and areas of stagnant water were doused with tons of noxious chemicals.

But it's the release of huge numbers of fish, even into water that soon evaporates, that many credit with helping to beat back the disease, which is now surging in other areas of the country.

"It's much better than chemicals that poison the environment," said Dr Mohammad Ayub, the director general of Punjab's fisheries department. "And anyway, chemicals soon get washed away by the rain."

A typical target the Punjab's fish team is an acre of murky water that forms every year in a depression squeezed between a flyover and brick factory in an unlovely outskirt of Lahore.

It is one of the hundreds of glorified puddles that fill during the monsoon season that are of little interest to anyone apart from wallowing water buffalos that make their home there.

Every few months a team led by a white bearded technician in an lab coat return to the pool, test the water and then release up to a thousand voracious tilapia fish from giant plastic bags partially inflated with oxygen.

Immediately on their release the surface of the water ripples with fish rising to gobble insects and the larvae that would otherwise quickly mature into mosquitoes.

The war on mosquitoes has demanded a significant effort by Punjab's fisheries department, which runs hatcheries to breed the vast quantities of fish seed required to keep mosquitoes at bay.

The effect has been dramatic with just over 100 cases reported in Punjab this year, compared with 20,000 in 2011. Officials say it has also curbed other pests, not just the Aedes mosquito that carries Dengue.

"Previously people could not sit outside in evenings on lawns but now they can sit comfortably because there are no mosquitoes," said Ayub.