Climate Change is Accelerating Vector-Borne Diseases

Sep 09, 2020 | Emily D'Angelo

In 1897, British doctor Sir Ronald Ross made the discovery that female mosquitoes transmit malaria between humans. This discovery allowed for an understanding of the malaria life cycle in mosquitoes, which was essential in building control efforts. Unfortunately, malaria continued to account for 2 to 5 percent of all deaths through the 20th century1. Although advancements in research and medicine have improved prevention and treatment of malaria, today nearly half of the world’s population is still at risk, thanks to a warming climate.

In addition to malaria, other diseases that are spread by mosquitos between humans include:

Risk of certain mosquito-borne diseases, as well as other vector-borne diseases, are changing along with our climate. Hurricanes, which are increasing in extremity and frequency, result in standing pools of water which serve as breeding grounds for mosquitoes. A prolonged rainy season could also increase the risk for the introduction and establishment of new vectors. Increases in temperatures across the country allow for the expansions of ticks as well as mosquitoes into areas where they previously did not exist. West Nile Virus and Lyme Disease provide great examples of how climate change has propagated vector-borne diseases in the U.S.

  • West Nile Virus was first detected in the United States in New York City, 1999. That summer had recorded the warmest July ever in Central Park in Manhattan, which increased the abundance of urban Culex mosquitoes2. Since then, is now the most common cause of mosquito-borne disease in the U.S. In 2018, over half of reported cases were neuroinvasive, affecting the brain or causing neurologic dysfunction.


Figure 1. Reported neuroinvasive cases of West Nile Virus disease by state, 2002-2014 (Source: EPA).
Figure 1. Reported neuroinvasive cases of West Nile Virus disease by state, 2002-2014 (Source: EPA).
  • Lyme Disease is the most common vector-borne disease in the U.S. The life cycle of ticks is strongly influenced by temperature, permitting climate change to increase the range of suitable tick habitats. Northern states (Maine, New Hampshire, Vermont) have experienced the largest increase in reported cases since 1991. Although most individuals diagnosed with early, acute Lyme are properly treated and make a full recovery, chronic Lyme patients face several challenges when accessing treatment. A 2018 report from the Tick-Borne Disease Working Group noted that 49.5% of chronic Lyme patients surveyed reported travelling 51 miles or more to see a treating doctor, and half of respondents saw at least seven physicians before their diagnosis of chronic Lyme was made. This rising disease fueled by our changing climate is burdensome on the healthcare system, but especially the individuals directly affected.
Figure 2. Reported cases of Lyme disease in the U.S., 1991-2014 (Source: EPA).

Vector control programs at local health departments (LHDs) play an important role in protecting public health. In addition to vector surveillance, control, identification, and research, these programs are also responsible for public outreach and education. Unfortunately, only 55% of LHDs provide vector control services, with these programs being less common in rural areas and areas with small populations (< 50,000 people). At these LHDs, many of which are still dealing with the budget and staffing cuts from the 2008 recession, the COVID-19 pandemic has impacted routine operations, reassigning limited staff to outbreak response and reallocating PPE which are used for chemical control applications.

NACCHO supports LHDs in protecting their communities from the bacterial and viral diseases transmitted by mosquitoes, ticks, rodents, and other emerging vectors. Through development of new tools and resources, research, policy statements, Stories from the Field, and more, NACCHO helps local health departments and local programs increase their capacity to address existing and emerging issues related to vector control and integrated pest management.

What can LHDs do?

References:

[1] Carter, R & Mendis, KN. (2002). Evolutionary and historical aspects of the burden of malaria. Clinical Microbiology Reviews, 15(4), 564 – 594.

[2] Brault, A.C. and Reisen, W.K. (2013). Environmental perturbations that influence arboviral host range. In Viral Infections and Global Change, S.K. Singh (Ed.). doi:10.1002/9781118297469.ch4


About Emily D’Angelo

Program Analyst

More posts by Emily D'Angelo

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