The health ministry may have denied doing so in Negeri Sembilan recently, but the release of Wolbachia-infected mosquitoes has been carried out previously and remains a useful measure to combat dengue.
In February 2017, then health minister Dr S Subramaniam announced his ministry’s plans to release mosquitoes carrying the micro-organism within a confined area to study its impact on dengue cases in the country.
One month later, Keramat AU2 in Kuala Lumpur was chosen for a pilot study on the effectiveness of Wolbachia mosquitoes for dengue prevention. The mosquitoes continue to be released in the area till today.
In recent years, Wolbachia mosquitoes have been released in multiple localities in Selangor, KL, Putrajaya, Penang, Kelantan and Melaka.
FMT looks at what the Wolbachia mosquitoes are and how they combat the spread of dengue.
Wolbachia mosquitoes
Mosquitoes do not naturally carry viruses. Instead, they pick them up by biting infected people. The mosquitoes then transmit these viruses when they bite again, which is how mosquito-borne diseases spread.
Only female mosquitoes bite humans, so they are the ones that transmit viruses. The Aedes aegypti mosquito is the main transmitter of dengue, Zika and yellow fever viruses.
Wolbachia is a micro-organism that lives naturally in the reproductive organs of insects. It is said to be found in about half of the insect species, including mosquitoes, fruit flies, moths, dragonflies and butterflies. The bacteria is not harmful to humans or the environment.
Injecting the Wolbachia bacteria into the Aedes aegypti mosquito eggs is seen as a method to prevent the spread of the dengue virus as the Wolbachia virus inhibits dengue from self-replicating within its carrier.
Combating dengue
Citing data from the national dengue surveillance system, virologist Kumitaa Theva Das of Universiti Sains Malaysia said a comparison of the incidence of dengue between 2013 and 2019 showed on average a 40% decrease in cases at all Wolbachia mosquito release sites.
“In one of the release sites, where dengue cases were high previously despite intensive community engagement and fogging, the Wolbachia mosquitoes successfully reduced dengue cases.
“Fogging by the local health authorities was no longer even considered necessary, indicating the success of this method in Selangor,” she told FMT.
Kumitaa said the strategy of releasing Wolbachia mosquitoes has shown promise and should be considered for implementation on a larger scale.
Expanding programme
On May 30, deputy health minister Lukanisman Awang Sauni said the ministry would be expanding the release of Wolbachia-infected mosquitoes to states that have seen an increase in dengue cases.
He said such mosquitoes had been released in 27 locations in KL, Selangor, Melaka and Penang, adding that the mosquitoes would also be released in Sabah.
Lukanisman said the ministry will continue to monitor the effectiveness of Wolbachia mosquitoes in preventing dengue.
He said the communities residing at release sites must be educated to ensure that the mosquitoes are not killed as their presence is a safe and effective method to combat dengue outbreaks.