The Zika virus is far more prevalent in Southeast Asia than many nations are willing to admit, according to a leading Australian scientist. Scott O’Neill, dean of science at Monash University in Melbourne, said Asian nations might be in denial regarding concerns that Zika could threaten their tourism revenue.
O’Neill, an expert on insect interactions with bacteria and their potential use in controlling mosquito-transmitted diseases, is in charge of a global collaboration working on eliminating the threat of the Zika-carrying mosquito Aedes aegypti.
“It’s telling that the World Health Organization congratulated Thailand for coming out and announcing the first case of microcephaly from Zika just recently,” he added. “It was a pretty pointed comment to the other countries in the area that are all trying to ignore it and not say anything about it, because they’re worried about tourism.”
First identified in Uganda in 1947, Zika has spread around the world with surprising speed in recent years. At least 73 countries and territories have reported evidence of mosquito-borne Zika virus transmission since 2007, and last year the disease erupted in South America.
In October 2015, Brazil reported a connection between Zika and microcephaly — a condition characterized by abnormally small heads and incomplete brain development at birth. More than 3,000 microcephaly cases have been confirmed in Brazil alone.
Even babies born with seemingly normal brains to Zika-affected mothers may suffer from future complications. In early October, it was reported that Brazilian babies who at first seemed to have escaped Zika-connected microcephaly, and whose heads were of normal size, were found to have delayed neuro-development.
Elsewhere, Thailand in September reported the first confirmed cases of microcephaly connected to Zika in Southeast Asia, a day after U.S. health authorities warned pregnant women to postpone non-essential travel to 11 Southeast Asian nations.
“Thailand’s diligence underscores the commitment of health authorities to the health and well-being of the Thai public, and provides a positive example to be emulated,” the WHO’s regional director, Poonam Khetrapal Singh, said in a statement. He urged other Asian nations to strengthen measures intended to detect and prevent the transmission of the Zika virus.
Zika is carried by the Aedes aegypti mosquito, an insect responsible for spreading a number of diseases, including yellow fever — a virus that killed more than 350 people in Angola this year. The mosquito can also transmit dengue and chikungunya — fevers that can be debilitating but are rarely fatal. Aedes aegypti is prevalent in tropical regions around the world, from Asia, Africa and South America, and even into the south of the U.S. and Australia’s far north.
O’Neill and his team at the non-profit “Eliminate Dengue” international research program at Monash have used naturally occurring bacteria called Wolbachia to prevent the Aedes aegypti mosquito from transmitting dengue and chikungunya, and more recently Zika.
First successfully tested in the lab, the Wolbachia method has worked in field trials that began in 2011, and trials have since been conducted in Brazil, Vietnam, Indonesia and Australia.
Mosquitoes carrying Wolbachia are released over a number of weeks to mate with the wild mosquito population. As the bacteria are passed from generation to generation, the percentage of mosquitoes carrying Wolbachia grows until it remains high without the continual reintroduction of Wolbachia mosquitoes.
Long-term monitoring has found that Wolbachia can sustain itself in wild mosquito populations, and in those areas where mosquito populations have high levels of Wolbachia, there has been no local transmission of dengue, and, it is assumed, no transmission of the other diseases carried by the insect, including Zika.
The “Eliminate Dengue” program is also testing methods for large-scale use of the Wolbachia method, which would roughly cost $1 per person, making it as affordable as possible. In March this year, the WHO recommended pilot deployments of the “Eliminate Dengue” program’s approach.
“We’ve had two scientific papers published showing that Wolbachia blocks Zika,” O’Neill said, adding that, even so, many Zika-affected nations have failed to express interest and take action in introducing the Wolbachia approach. “We find it interesting that a lot of affected countries really aren’t that switched on to what their various options are at the moment. I’m always surprised by that.”
Unlike other methods, for instance one that uses genetically engineered mosquitoes, the Wolbachia method is self-sustaining. Mosquitoes pass the bacteria on to their offspring, hence eliminating the need to continually pay for more of them to keep the viruses in check.
O’Neill described the genetically engineered mosquito method as similar to a subscription service for which communities have to keep paying, adding such a commercial approach “makes a good business model.”
Growing populations of people and mosquitoes, and increasingly easy and inexpensive travel, leads to the circulation of people who are moving viruses around, O’Neill explains.
Zika was relatively obscure until last year, when the virus began spreading rapidly in South America. O’Neill among other scientific experts warns that another, and potentially more dangerous virus, could appear and take hold in a similar manner in years to come.
“We know that there are a number of viruses this mosquito (Aedes aegypti) can transmit, some of them quite obscure,” O’Neill said. “I definitely think that in the future, there’s every potential for other Zika-like diseases to emerge.”