By Marlee Tichenor
With Zika cases anticipated to increase in the Northern Hemisphere as mosquito season hits soon and with the recognition of World Malaria Day on April 25th, it is important to think about how addressing the mosquito and its entanglements with humans is crucial to global health efforts. Many, including Bill Gates, have called the mosquito the deadliest animal in the world due to the diseases it can carry, which include dengue, yellow fever, West Nile virus, and chikungunya beyond the two mentioned above. These diseases kill an estimated 750,000 people per year. Additionally, there is a certain amount of urgency due to climate change, as the mosquito’s dominion is set to expand without effective control efforts.
Fighting Zika has required two major efforts: mosquito control and investment in case tracking. US funding is running low for both. In September 2016, the US Congress approved a $1.1 billion public health package to fight the Zika epidemic that had by then spread to much of the Americas. Within that public health package, nearly $400 million was earmarked for the Center for Disease Control to help state public health departments track microcephaly and Zika cases, $397 million to develop a vaccine, $394 million to control Zika-carrying mosquitoes, and $145.5 million to support global vector control programs. Much of this health care package was expected to last four years but is running out after eight months. A Senate panel has approved a bill for an additional $100 million for mosquito control, an important first step in filling this gap, but it must now go to the House and Senate for a vote.
Malaria was endemic in the southern states of the US until 1954. A large component of the 1947-51 National Malaria Eradication Program of the Office of Malaria Control in War Areas (which would become the CDC) was spraying homes and residential areas with insecticides like DDT, along with draining the breeding grounds of the Anopheles mosquitoes that carry malaria. As a part of this effort, Anopheles also acquired the name “Annie Awful,” as seen in the imaginative anti-malaria campaign poster above meant to encourage people to use mosquito nets. Although malaria is eliminated within the US, the Anopheles mosquito population has in fact rebounded in the decades since. Particularly in those states bordering the Gulf of Mexico, close surveillance of Anopheles mosquito populations and malaria cases has kept malaria from rebounding as well.
Zika is spread by Aedes mosquitoes, which also carry dengue, yellow fever, and chikungunya. While Anopheles are understood to use marshes and clean standing water as breeding sites, Aedes are understood to be more urban, using small pots of water or puddles as breeding sites. Aedes – affectionately called the “cockroach of mosquitoes” – are proving to be a much more formidable foe, as the chemicals being used to fight them are not as effective as would be hoped. DDT was banned for use in the US in 1972 due to its environmental impact, and many less effective insecticides have taken up its role in the meantime.
In the wake of this, public health officials have been advocating different ways of controlling the mosquito population. This includes releasing mosquitoes infected with naturally occurring Wolbachia bacteria, which keep larvae from making it to adulthood and which is not harmful to humans. Also last year, the Florida Keys Mosquito Control District put a vote up to constituents about whether they should release Aedes mosquitoes that had been genetically engineered by the biotech company Oxitec to produce progeny that would also not make it to adulthood. Monroe County residents voted 57% against the effort due to fears about genetically modified organisms.
The politics of public health interventions are complex on multiple levels. In the current political environment in the US, funding for health care and interventions is set up to be a constant battle, as Congress debates what role the government even has in the American people’s health. Once funding is secured, however, there are more battles to fight in order to address diseases that rely on a creature as intimate to Americans in the summer as the mosquito. Populations are understandably wary of bacteria-infected or genetically-sterile mosquitoes being released in their backyard, and controlling mosquitoes will require active public engagement.