KUALA LUMPUR: The number of dengue cases could see a downward trend after the Health Ministry kicked off a programme to release Aedes mosquitoes injected with Wolbachia bacteria in an effort to stamp out the disease.

This follows a pilot project in 2017 carried out in eight areas in Selangor that showed reductions of between 50% and 80% of dengue cases in each location.

Health Minister Datuk Seri Dr Dzulkefly Ahmad said releasing Wolbachia-infected mosquitoes could also reduce dependence on the use of insecticides to control the mosquito population.

"Insecticides may have other side effects," he said at the launch programme at Apartment Sri Rakyat in Bukit Jalil where 35 cases of dengue were detected last year and went through at least three episodes of the disease this year with about 15 cases.

Dr Dzulkefly said in the past five years, 123 cases were detected in the area it in third place of areas with the highest number of dengue cases in the Federal Territories and Kuala Lumpur.

He added that there was a 92.4% increase in dengue cases nationwide in the first six months of 2019.

"There were 62,421 dengue cases between Jan 1 and June 29 this year with 93 deaths compared to 32,435 cases with 53 deaths in the same period last year," he said.

Malaysia is the second country after Australia to use the bio-control strategy.

The programme involves placing release containers containing Aedes mosquito eggs infected with the bacteria at 11 locations in Kuala Lumpur, Putrajaya and Selangor before releasing the hatched insects in phases.

Wolbachia-infected Aedes mosquito eggs will be placed in containers to hatch. – SAMUEL ONG/The Star

The Wolbachia bacteria stops the dengue virus from replicating so the mosquito does not spread the virus when it bites.

When an infected female mosquito mates with an uninfected male, they will produce Wolbachia-infected mosquitoes.

It is the same when both infected mosquitoes mate.

But when a Wolbachia-infected male mosquito mates with an uninfected female, the eggs won't hatch.

The bacteria does not pose any danger to humans.

The Health Ministry is expected to extend the programme to other states in September.