Mosquito Control: Toolbox of the Future

Senior research scientist Dr. Karl Malamud-Roam chose a novel way to introduce and explain an important subject: The Mosquito Control Toolbox for the Future and the Barriers to its Growth and Innovation. When the Rutgers University researcher began his presentation at NPMA PestWorld last October, he sang three musical themes from popular Broadway and Hollywood productions. His renditions were “The Impossible Dream,” from Man of La Mancha, “If I Were a Rich Man,” from Fiddler on the Roof, and “The Good, the Bad and the Ugly,” from the spaghetti western film of the same name.

He maintained that total mosquito eradication is still an impossible dream. “There will always be a need for mosquito control because we can never completely get rid of this pest, at least for the next hundred years or so,” he stated. “It’s possible that some of today’s existing technologies or new technologies will lessen the risk of some mosquito-borne diseases, but we’ll probably always need to control disease-carrying mosquitoes.

“As effective as these might be,” he said, “they likely won’t be perfect, because our growing population will include many more people vulnerable to these diseases.” Even today the number of vulnerable people is much higher than it was 100 years ago, he stated. “People now tend to be more urbanized, and modern transportation takes more people around the world, making them even more (likely to be) exposed to disease-carrying mosquitoes.”

The relevance of singing If I were a rich man, he said, lies in the fact that over the past few decades, regulatory requirements involving pesticides have increased, yet private industry has seen inadequate financial incentives to invest heavily in the field.

Costs are high, increasing and unpredictable, he observed. “And while it’s important to ensure pesticide safety and public confidence, high regulatory costs can stifle innovation.” Because of this and the fact that mosquito control is a relatively small market, he maintained that there aren’t nearly enough R&D dollars available to create a new toolbox that the industry should ideally have.

“There’s not enough money for product retention in the face of regulatory requirements, nor is there enough money to buy and use the products we do have. And we certainly don’t have enough dollars available to develop mosquito control tools that carry no human risk, have no environmental impact and completely control this pest species.

“We must realize,” he said, “that in our present situation, financial resources will be very limited, and one of the factors we will need to deal with is carrying capacity — how many tools we will have in our toolbox. For the pesticide industrial sector to stay in business, the costs involved to manufacture mosquito control products, warehouse them, market them and register them is great. So, the reality is there will be a limited number of tools available to you. And the big question is: if you want to bring in new tools, will you have to get rid of some existing tools? Where and how can you find the proper balance between innovation and retention? So where do I see the future of mosquito control? It’s good, it’s bad, and it’s ugly.”

During his speech, Malamud-Roam touched on several important mosquito control techniques: avoidance, sanitation, chemoprophylactics and netting, and discussed the present-day mosquito control status and its outlook.

HABITAT REDUCTION. He explained that the technology in the first half of the 20th century involved reducing the habitats of mosquitoes, utilizing fish to eat mosquito larvae and treating with petroleum hydrocarbon oils, and some simple synthetic and botanical materials. The second 50 years saw new technology come on board, including various classes of synthetic organic chemicals, more effective petroleum oil formulations and IGRs. Synthetic pyrethroids and microbial control agents were developed and utilized. Among these control agents, petroleum oil formulations were effectively used.

“Prior to 1900,” he stated, “people didn’t know a great deal about mosquito-borne disease but many decided not to travel to dangerous, under-developed places, such as third-world nations. They knew that people caught diseases there so they simply avoided these places.”

Good sanitation is also paramount in the control of mosquitoes, he emphasized. “When the Panama Canal was built, the United States — not France — did the job. The reason? Our country’s sanitarians were able to drain standing water from the canal construction sites better than the French, and this protected workers from Yellow Fever. It was a big job, but feasible at the time. Today, draining standing water is more difficult because there are bigger urban populations, and the storm drain and trash removal systems are inadequate to do the job properly.”

FIRST-HAND EXPERIENCE. Malamud-Roam told his audience of an area-wide mosquito control effort he participated in several years ago. “It was a major project in New Jersey that devoted public funds to stopping the Asian tiger mosquito in an urban setting that was in a rainy, warm environment with inadequate trash collection. The first thought was to utilize the old methods of drainage and sanitation. These worked well, but only for a few weeks. It was a good strategy, but it was too labor-intensive to be maintained, and it is unlikely that it would work any better in a poorer nation. You have to understand its limitations.”

Chemoprophylaxis, he said, can be an important prevention tool for mosquito-borne disease, but is also limited. “If you can’t eliminate mosquitoes, you can sometimes stop associated diseases with vaccines, which is a CDC recommendation. Not long ago the U.S. Congress finally approved supplemental dollars for mosquito-borne Zika prevention, and a large amount of that money is devoted to accelerated vaccine development. Of course, that’s a good thing,” he said, “but it won’t be ready for this disease for at least two years.”

OLD TOOLS THAT WORK. “The old tools of mosquito nets and screens are still used as physical barriers and still work,” according to Malamud-Roam, “as does their modern analogy: chemical repellants. These are great tools.”

Will nets and screens work well for Zika protection? “I think screens have a real role in this effort,” he commented. “But I’m not so sure about nets. However, mosquito nets have been proven extremely successful in reducing malaria. Statistics for the 15-year period starting in the year 2000 demonstrated that malaria deaths dropped by more than 50 percent. Malaria is the single most deadly infectious disease in the world and its death rate has been significantly reduced due to our efforts at vector control, and in particular the use of bed nets and indoor residual pesticides. But malaria mosquitoes bite at night, while Zika virus carriers bite mostly during the day, so we don’t expect the same level of success.”

Discussing the utilization of smoke from mosquito coils to keep mosquitoes away, he said that has been around for a long time and is still in the modern mosquito control toolbox.

“I believe vapors will play a large role in the mosquito protection system in the future,” Malamud-Roam said. “People using this protection won’t need netting and won’t need repellants on their skin.”

THE NEXT 25 YEARS. Looking ahead to the next 25 years or so, Malamud-Roam said there are some application and tool innovations now being developed that should be helpful in future mosquito control programs.

“These include deltamethrin aerial applications, which utilize an insect-active pyrethroid; ULV (ultra low volume) larvicide technology; and treated curtains — a cross between bed netting and screens. There are also a number of indoor residual sprays, but research is needed to see which are best to be utilized routinely.”

There are new tools being developed in the ‘attract and kill’ category, he said. “This is a big paradigm for the future. The logic is this: If current pesticides have to find mosquitoes, they may not do a good enough job. But if the mosquito finds its way to pesticides, the likelihood is a reduction of non-target risks. Attract and kill tools include lethal ovitraps, sticky traps, surveillance traps and attractant toxic sugar baits.”

He also noted the development of new tools that involve mating disruption, including genetically modified insects, radiation, chemosterilants and pheromones.

Malamud-Roam also sees a mosquito control future utilizing improved petroleum oil formulations, insect growth regulators and microbial control products, as well as new vaccines and molecular entomology techniques being developed for the market.

The author is a freelance writer based in Milwaukee, Wis., and a frequent editorial contributor to PCT magazine.