This Bites: Climate Change and the Risk of Vector-Borne Disease

Contributors: Nobi Kennedy, Kelly Morton, Bamidele Osamika, Leah Ross, Mitch Singstock, and Savannah Sullivan

This piece is part of Green Umbrella’s 2024 PSA Campaign on climate health impacts, highlighting a recent report done with Scioto Analysis which was supported in part by a bi3, HealthPath, and Interact for Health Data for Equity Grant.

In the Midwest, the only place you’re usually going to see a live flamingo is a zoo or bird sanctuary. But in the fall of 2023, hurricane winds blew a flamboyance of flamingos (yes, that’s what it’s called) off their migratory course and were spotted in the wild at Caesar’s Creek Park Lake near Waynesville in Southwest Ohio. Although a memorable moment for bird enthusiasts in the area, the reality behind their presence is disquieting: changing climate is disrupting animal behavior and their ecosystems. Our increasingly unpredictable climate will continue to disrupt animal behavior and destabilize ecosystems, displacing creatures great and small – and not all are as fun to host as flamingos. 

As our region becomes warmer and wetter, infectious disease-carrying creatures – known as vectors – will find comfortable homes in areas that were previously inhospitable. Take the 2016 anthrax outbreak in Russia’s Yamal Peninsula, a remote corner of Siberia above the Arctic Circle. An unexpected heatwave thawed permafrost, releasing dormant anthrax spores that infected reindeer and the humans living alongside the herds. Ensuing studies show that these events are likely to continue to crop up with more frequency and underscore how warming climates can awaken hidden dangers. So, while flamingos can be a delightful surprise, the broader impacts of climate change demand urgent attention.

Climate Change: Giving Vectors a Home

A biological vector is a living thing that carries a disease-causing agent (virus, bacteria, infectious spores, etc.) between different species – for example, a rabid dog is considered a vector because it can transfer rabies to humans and other animals. Because of climate change, vector-borne illnesses – diseases primarily spread through vectors – are an emerging concern for our region, in both rural and urban communities. Climate change is making the Midwest warmer and receive more precipitation, creating an environment more welcoming to pests like biting insects and rodents, which are extremely common vectors for illness.

This post will focus on vector-borne diseases from biting insects, specifically ticks and mosquitoes. These insects thrive in warmer climates; cold and frigid weather both prevents breeding and can kill them off, meaning that warmer autumns and winters are not as effective at controlling the population. 

In addition to aiding population growth of the pests already existing in our region, climate change is driving more species of biting insects north from tropical, subtropical, and desert climates. In some cases, rising temperatures can even change the typical behavior of biting insects; for example, in higher temperatures, a species of brown dog tick prefers to bite humans instead of dogs, increasing the possibility of contracting Rocky Mountain Spotted Fever (see below). This tick is typically found in the southwestern US, but their range is expected to move northward as climate change causes average temperatures to rise.

While the impact of many illnesses will change as the climate does, these vectors and the diseases they carry are likely to make a significant impact on our region – including exposure to diseases traditionally considered rare in the continental United States, like dengue fever and malaria.

Vectors in our region: Ticks

Lyme Disease

With 476,000 infections a year, Lyme disease is the most commonly reported vector-borne illness in the United States. It is caused by the bacteria Borrelia burgdorferi and transmitted by blacklegged ticks (also known as deer ticks). People who spend time outside in wooded or grassy areas are most at risk of becoming exposed to Lyme disease.

The most common early symptoms of Lyme disease (within 3-30 days) are a “bulls-eye” rash, a single red circle that spreads from the site of the tick bite; extreme tiredness and muscle aches; headaches; and fever. Because the rash can be easily missed, and the other symptoms mistaken for other common infections, Lyme disease can pass unnoticed for months. 

If left untreated, symptoms of the later stages of Lyme disease can show up 3-10 weeks and even 2-12 months after infection. New symptoms can include disruption to the immune system that causes irregular heartbeats, eye pain, or vision loss; muscle weakness in the face, hands, or feet; and arthritis in large joints, especially the knees.

Diagnosing Lyme disease can be difficult if the bulls-eye rash is missed or absent; some people can suffer for years before being diagnosed. Treating Lyme disease consists of rounds of antibiotics. There is no vaccine for Lyme disease; the best defense against Lyme disease is prevention.

Rocky Mountain Spotted Fever

Spread by several species of ticks, Rocky Mountain Spotted Fever (RMSF) is one of the most deadly types of tick-borne disease. RMSF can be deadly within days if not treated with proper medical care; before the proper antibiotics were available, case fatality rates ranged from 20-80%. 
Early symptoms appear in the first 1-4 days and can manifest as a rash, high fever, severe headache, muscle pain, swelling around the eyes and back of the hands, and gastrointestinal issues including nausea, vomiting, and anorexia. After day 4, symptoms can include coma, swelling of the brain, organ failure, and tissue death requiring amputation. Because of the severity and rapidity of the disease progression, delay in antibiotic treatment can result in permanent damage or death. There is no vaccine for RMSF; the best defense is prevention.

Vectors in Our Region: Mosquitos

Today in the United States, mosquitos in the United States are seen more as a nuisance on a summer’s evening than a serious health risk, but that’s not the case throughout history or the rest of the world. In 2022, the WHO estimates there were 249 million cases of malaria across the globe and 608K deaths in 85 countries – and mosquitos are the malaria parasite’s vector.

Malaria

Malaria used to be so prevalent in the U.S. that the primary mission of the newly formed Communicable Disease Center (CDC) was to eliminate malaria as a major public health problem. Total elimination of transmission was achieved, and the U.S. was declared malaria-free in 1949.

There are 2000-2500 cases of malaria in the United States annually linked to travel in areas where the disease is currently endemic, such as Africa south of the Sahara, Southeast Asia, and parts of Oceania. But in 2023, locally-acquired cases of malaria were reported in Florida, Texas, and Maryland. Climate change is making it easier for the Anopheles mosquito to infect humans in the United States.

The most common symptoms of malaria include fever, chills, nausea, muscle aches, tiredness, and flu-like illness. These symptoms can appear as early as one week after infection or as late as a year or longer. If left untreated, malaria can cause kidney failure, seizures, coma, and death. There are malaria vaccines available for use in children in high transmission areas, and those who know they will be exposed to malaria can take medications to prevent infection. Malaria can be cured if diagnosed and treated promptly.

Dengue Fever

Dengue fever – also known as break-bone fever due to its severe pain symptoms – is mainly found in tropical and subtropical areas throughout the world, but last year, locally acquired cases of dengue popped up in California, Texas, and Florida. Dengue is a virus spread through the bites of the Asian tiger mosquito, Aedes albopictus, an invasive species that is expanding in distribution throughout the world. In the United States, the northernmost established populations of the Aedes mosquito are in New Jersey, southern New York, and Pennsylvania – for now. Climate change is making more of the U.S. hospitable to these insects; by 2070-2099, the Midwest will be a suitable place for dengue-carrying mosquitos to survive and thrive.

While common symptoms of dengue are fever, headaches, and severe body aches, up to 75% of people infected can show no symptoms at all – meaning that there is potential for more mosquitos to bite them and go on to infect more people. 1 in 20 infected people who experience symptoms will develop severe dengue, which can be life-threatening within hours. Common signs of severe dengue are vomiting, bleeding, and stomach pain. Most people recover from dengue after about a week, but recovering does not offer immunity from being infected again. 

There is no prescribed treatment for dengue aside from pain management, and severe cases of dengue require immediate medical attention. At this time, a vaccine is available in 20 countries only for those who have already been infected with dengue and recovered, though widespread approval of a dengue vaccine for anyone, regardless of prior infection, is currently in process.

West Nile

West Nile Virus is a significant vector-borne illness and a particularly serious threat in our region. It is transmitted through the bite of a mosquito that has contracted the virus by feeding on birds that carry the disease, including crows or jays. Most infected individuals show no symptoms, but about 20% experience fever, headache, body aches, joint pain, vomiting, diarrhea, or rash. Severe cases can develop neurological complications such as encephalitis or meningitis, which can manifest as high fever, neck stiffness, disorientation, and even paralysis. Diagnosis is typically confirmed via lab tests that detect the virus or antibodies in the blood or cerebrospinal fluid. 

Currently, there is no specific treatment for WNV and care is largely supportive. Over-the-counter pain relievers can alleviate some symptoms while severe cases may require hospitalization for intravenous fluids, pain management, and prevention of secondary infections.

What You Can Do Right Now

The best way to protect yourself from infection is prevention! Wear protective clothing when going through wooded or grassy areas. Apply bug spray to ward off mosquitoes, ticks, and biting insects. Avoid touching wild animals, including squirrels, rabbits, chipmunks, and deer – they can be carriers of vectors like fleas and ticks. Directly after returning inside, check your body and clothing for any sneaky ticks (they like to hide in hair, behind ears, and behind arms and legs). 

Stay alert! Keep a mental note of any possible exposures to vector-borne illnesses and monitor any bug bites. Know the signs and symptoms of vector-borne diseases; if you become ill after an exposure, make sure to tell your doctor where you were so they can take the exposure into consideration. More information and resources about vector-borne illnesses are at the bottom of this post.

What We Can Do As a Community

Taking action now will be a big step towards defending our community from vector-borne disease. Advocating for more CDC funding and vaccine availability is imperative to prepare for a future with more of these diseases. For those in public health and policy, being aware of historical and indigenous approaches to these diseases can be a big help in learning how to handle the vectors and the pathogens they carry. Effective food waste, landfill, and stormwater management are necessary to help control rodent and insect populations that could become possible vectors for disease.

Strong public policies, such as housing and land use regulations that support the management of these issues, are essential. Implementing comprehensive vector and disease surveillance programs and robust vector control initiatives will help in early identification and response. Early warning and monitoring systems will facilitate timely interventions to prevent outbreaks. Public awareness and engagement campaigns are vital for educating the community on preventative measures and responses. 

As the threat of vector-borne illness grows in our region, education remains key to keeping the public aware and helping to prevent infection. Share information on how to prevent, recognize, and treat diseases moving into our region with the public, and issue transparency about information on infection rates and research on evolving instances with health professionals.

Learn More

Webinar: Climate Change and the risk of Vector Borne Illnesses

Watch the recording of the fourth installment of the Climate Health Public Service Announcement Webinar Series, Climate Change and the risk of Vector Borne Illnesses, on YouTube. Our guest speakers are Allison T. Parker, PhD Assistant Professor of Biological Sciences at Northern Kentucky University and Joshua B. Benoit, Ph.D. Professor of Biological Sciences at University of Cincinnati.

Resources

• Climate Change and Insect Vectors
• Protect yourself from vector-borne disease
• Types and Symptoms of vector-borne disease

Infographics – download and share!

Federal assistance programs:

• CDC Division of Vector Borne Disease
• Strategies for Improving Rural Health
• ReConnect Loan and Grant Program