Mosquito Borne Illnesses Require Multifaceted Approach from Public Health Officials

September 14th, 2016

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By Christie Chung, CHHS Research Assistant

From world-class athletes skipping the Olympics to Florida theme parks handing out complimentary insect repellent, the Zika virus has prompted much concern and anxiety. However, the disease most widely known for its link to birth defects is just one of several mosquito-borne illnesses currently threatening global health.

Mosquito-borne diseases pose a number of unique problems to public health officials. For one, there are approximately 3,500 different species of mosquitoes endemic to regions across the planet; many are vectors of transmittable diseases. Aedes aegypti alone is responsible for outbreaks of Zika, yellow fever, chikungunya, dengue fever, eastern equine encephalitis, and West Nile virus. Each disease carries its own unique set of (often delayed) symptoms and risk factors. For public health organizations, efforts to contain outbreaks are burdened by the need to tailor responses to address the specific problems presented by each disease.

For instance, since December 15, 2015, there have been over 2,000 reports of yellow fever in Angola and the Democratic Republic of the Congo. In large part, the outbreaks have been aggravated by rapidly diminishing vaccine stocks. The production of yellow fever vaccines is a time-intensive process that requires inoculation of sterile, embryonic chicken eggs with the virus—a process that takes approximately 12 months. Absent the ability to produce the vaccination quicker, the World Health Organization (WHO) is researching the possibility of partitioning current doses by 1/5 of their normal quantities. Referred to as “fractional dosing,” the reduced dose would not confer lifelong protection, but it would protect vaccinated individuals for at least 12 months. The WHO’s response to heavily strained vaccine stocks and the threat of international transmission is an example of the flexibility and resourcefulness required from public health officials when dealing with the containment of outbreaks.

The rapid, geographic spread of mosquito borne diseases is another factor that greatly frustrates efforts at containment. Increased globalization and global climate change has eroded the protection that natural borders once conferred. Shifting weather patterns open up previously inhospitable habitats, while the free flow of persons and goods across national borders drastically increases the range of diseases. Once confined to the border area between Tanzania and Mozambique, Chikungunya (derived from the Kimakonde phrase for “to become contorted”) virus has since been reported in 46 states and the District of Columbia.

Consequently, the successfulness of mosquito control measures is dependent on the extent to which agencies are able to coordinate on an international, federal, state, and local level. For the public, the operations of public health organizations may seem largely reactive—identify outbreaks and contain. However, effective disease control requires proactive initiative.  As part of their work, the Centers for Disease Control (CDC) must closely monitor emerging trends, larval populations, and potential sources of mosquito born illnesses. This requires maintenance of a large network of experts in fields ranging from epidemiological studies to veterinary medicine.

The environmental facet of disease control is yet another tax on the public health response. For as much as they are considered pests, mosquitoes—like all organisms—fulfill an important ecological niche. Complete eradication of the insect would impact entire ecosystems. For instance, in the tundra, caribou select migratory paths based on wind patterns to avoid mosquito swarms—mosquitoes draw up to 300 milliliters of blood a day from each animal in the herd. Deviations in the route of caribou would have a major impact on the ecology of the Arctic valley, including the growth of lichens, transportation of nutrients, and feeding patterns of wolves. In addition to consideration of ecological concerns, EPA officials must contend with emerging insecticide resistance. Monitoring levels of resistance to insecticides, testing existent insecticides to ensure they sufficiently break down in the environment, and developing stronger insecticides are all factors that must be accounted for in disease control.

Ultimately, in spite of the best efforts of public health organizations, mosquito-borne illnesses are still characterized as “especially difficult to predict, prevent, and control.” With many mosquito borne illnesses lacking a cure, public awareness remains one of the best means of prevention. As with all campaigns of public information, however, care must be taken to educate and alert without needlessly inciting panic.

A week from now, a month from now, a year from now, Zika may or may not be front page news. Mosquito borne illnesses, the problems they present public health officials, and their impact on human populations, however, are decidedly here to stay. To that end, the basics of mosquito safety remain more important than ever—use DEET-based repellants, dress to minimize skin exposure, and avoid outdoor activity near dusk and dawn.

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