As Hawaii Island’s dengue fever outbreak marches on, some isle residents have been critical of efforts by state and county agencies to contain the mosquito-borne virus.
As Hawaii Island’s dengue fever outbreak marches on, some isle residents have been critical of efforts by state and county agencies to contain the mosquito-borne virus.
Public health officials argue the Big Island poses unique challenges to their control efforts. With its large geographic area and spread-out populations, spraying insecticides and larvicides is only successful in controlling mosquito populations within limited areas on the island. Much of their control plan relies heavily on the public making a concerted effort to avoid contact with mosquitoes, which often is easier said than done.
But imagine if there were a way to let Mother Nature help with mosquito-control efforts. That’s the idea behind research being done by professor Scott O’Neill of Monash University in Melbourne, Australia, and professor Scott Ritchie of James Cook University in Cairns, Australia.
In 2014, the pair published the results of their work in the scientific journal of the Australian Entomological Society. “Rear and release: a new paradigm for dengue control” presents a new method for dengue control that focuses on rearing Aedes aegypti mosquitoes that have been infected with a bacteria called Wolbachia, and then releasing them into the wild, as opposed to widespread spraying to reduce their population.
It might seem counterintuitive to release more mosquitoes, but the research showed that within just a few years the Wolbachia virus spread to nearly 100 percent of the mosquitoes in test areas. And that’s a very good thing, Ritchie explained during a Monday afternoon phone interview.
“Using our Eliminate Dengue approach, you’re not getting rid of the mosquito. You’re introducing bacteria which reduces its capacity to carry the virus so they won’t be very good vectors,” he said.
Aegypti mosquitoes, which health officials identified as one of two likely carriers of the disease in Hawaii, are infected with Wolbachia and the dengue fever virus is then not able to spread to human hosts, thus effectively stopping the life cycle of the disease, which relies on hopping back and forth between humans and mosquitoes to propagate.
Beginning in 2010, Ritchie’s and O’Neill’s Eliminate Dengue research program released male aegypti mosquitoes into neighborhoods near Cairns and watched as the Wolbachia bacteria rapidly spread among the local populations of mosquitoes. Within just a few months, many locations reached levels of Wolbachia infection near 100 percent.
Since then, there have been no outbreaks of dengue fever in the areas where Wolbachia infected mosquitoes are established, Ritchie said. During a normal wet season, those areas are highly prone to outbreaks.
The scientist, who earned the childhood nickname “Itchy Ritchie” because of his fascination with mosquitoes, said he couldn’t be sure how the process might work in Hawaii, as there are so many factors that must be taken into account.
“I’m not there on the ground, so I’m not sure what the situation is, and what the mosquito-human-dengue ecosystem is like there,” he said. “But if aegypti is the vector spreading dengue, I think you guys should do whatever you can do to try to take care of the aegypti situation.”
Currently, there is a lot of exciting research being done around the world regarding mosquitoes and dengue fever, and the Wolbachia solution is just one possible approach, he said.
“Rear and release, that’s got legs. There are various different ways of rearing mosquitoes for release to control viruses,” Ritchie said.
The Wolbachia method could be an attractive one on the Big Island, especially for people opposed to widespread spraying of insecticides or those afraid of methods that make use of genetically modified mosquitoes.
“I will say this, it’s more natural in the sense that you are using only the mosquito to fight the mosquito,” he said. “You’re not using pesticides or anything else to go with it. It’s a more green technology.”
Meanwhile, the state Department of Health reported Monday no new confirmed dengue fever infections on Hawaii Island.
As many as three confirmed cases remained infectious, having experienced onset of the illness Jan. 8. A total of 220 confirmed cases are no longer infectious, with illness onset ranging between Sept. 11, 2015, and Jan. 7.
Email Colin M. Stewart@hawaiitribune-herald.com.