Grow flowers to kill Aedes: expert
Veeramohan Supramaniam, a spokesman for the Malaysian Association of Environmental Health (MAEH), said mosquitoes would often become sluggish upon feeding on nectar, making them easy prey to bigger insects, spiders, frogs and lizards.
“We have to re-establish these creatures in the urban landscape with flowering decorative plants rather than palm trees and cactii that don’t flower,” he said.
He said the relevant authorities are moving towards such a change.
Veeramohan, through MAEH, has been conducting field research and epidemiological studies to learn more about the dengue threat and is engaged in advising the authorities on ways to refine the existing prevention programme, which is based on World Health Organization (WHO) guidelines.
He said the WHO guidelines focused on outbreaks at residential units. He acknowledged that programmes based on those guidelines had helped contain the dengue menace, but only to some extent.
With the changing urban landscape of Malaysia, he said, the “old paradigm has to be questioned and re-tested” and a method taking account of new research and data should be applied.
Pioneer methods
He said a dengue outbreak was something “totally preventable”.
One of the programmes he recommends is bio-diversification, and that would include the greening up of urban areas with flowering plants. He said this would have to be implemented by local governments because vacant land and open areas in urban centres are not under the purview of the Health Ministry.
Having already worked with the Kuala Lumpur City Council and having seen great reductions in dengue cases and hot spots, Veeramohan is confident that the pioneer methods that he and his associates advocate will reduce overall cases in a given city or town within weeks.
“We are working towards these new methods of dengue management, which are preventive, by getting rid of the Aedes breeding grounds,” he said.
“Its a simple process. Local authorities will serve a notice to owners of land that might serve as breeding ground, failing which they will clean it up themselves and claim the cost later.”
MAEH seeks to empower the public with education on good practices in fighting dengue. Veeramoham urged citizens to contact the association through their neighbourhood associations to request lectures or seminars.
He said programmes based on the WHO guidelines had resulted in a drastic reduction in dengue cases among people who tended to be confined to the home – the very young, the very old and those with limited mobility.
“Conversely, we found that people who are very mobile, especially school children, are exposing themselves to bites from mosquitoes in the open spaces,” he said.
“These open space mosquitoes are almost never a target of control by the Ministry of Health because open spaces are local authority areas.”
Different species
MAEH has found through research that the new dominant vector of the dengue virus is an outdoor native species called Aedes albopictus, commonly known as the Asian Tiger Mosquito.
“This mosquito is not the species that is emphasized in WHO programmes. They emphasize Aedes aegypti, an important species nonetheless.”
Veeramohan said repeated control measures in residential areas, including fogging had helped lower the Aedes aegypti’s breeding rate due to the fragile nature of the species.
Speaking of Aedes albopictus, he said this species would pick up the dengue virus from healthy human carriers (one or two days prior to showing symptoms) during feeding outdoors in the city, and could pass on the infection to healthy people.
Veeramohan also revealed what he called an “inconvenient truth” from his research – that both the species don’t lay their eggs on water, contrary to popular belief.
“The lay their eggs on the damp inner walls of containers and even on flat surfaces such as on the ground, and then wait for rain water to flood them,” he said.
“The longer the eggs have stayed dry, the faster they hatch when flooded with water. They can stay dried up under vegetation cover and remain viable for two to three years.”
The “double jeopardy”, according to Veeramohan, is that these eggs are also infected with the dengue virus, passed on by the parent mosquitoes. Upon maturing, the mosquitoes that hatch from them would go on to infect new victims.
Originally part of the ecosystem of the tropical rain forest, Aedes albopictus’ population has boomed with the removal of its natural predators resulting from the rapid clearing of forests for residential and commercial development, according to Veeramohan.
On top of that, heavy fogging has also reduced the number of dragonflies, which he says is one of the best predators of mosquitoes, both in water and in the air.
