Kissing Bugs and the New World Screwworm—Unwelcome Climate Migrants

“Kissing bug disease, which causes everything from a furious, excruciating itch to a sudden stroke or deadly heart attack, is endemic in the United States…”

Beth Dalbey, staff writer, Patch, September 18, 2025

“NWS [New World Screwworm] infestations are very painful. If you have an NWS infestation, you may see maggots around or in an open wound. They could also be in your nose, eyes, or mouth. Tell your healthcare provider of any recent travel to Central or South America, the Caribbean, or Mexico.”

USDA’s New World Screwworm. What You Need to Know, August 27, 2025

A variety of human pathogens (viruses, bacteria, fungi, and parasites) have migrated to new geographic locations made more hospitable to them by warming temperatures or increased humidity. In particular, ticks and mosquitoes, the vectors of many human infectious diseases, are having a “field day” because of climate change (global warming).  (See, e.g., “How Climate Change Fuels Infectious Diseases,” Germ Gems, April 21, 2021;  “Microbes and Climate Change,” Germ Gems, December 13, 2023).

Now our warming climate has fostered the arrival of two insects to the U.S. They are reduviid bugs, aka, “kissing bugs,” that transmit Trypanosoma cruzi, the parasite that causes Chagas disease, and Cochliomyia hominivorax, the New World screwworm (NWS), a parasitic fly whose larvae feed on living tissues, including those of humans. These recent migrants –one of which has established permanent residence—are the subjects of this week’s post.

Chagas disease. The parasite Trypanosoma cruzi causes Chagas disease, aka American trypanosomiasis. T. cruzi is spread mostly by the infected feces of insects known as “kissing bugs,” deposited in bites, cuts, or openings like the eyes. (Because these insects cannot bite through clothing, they generally feed on tender areas of the face thus the name “kissing bugs.”) While Chagas disease is largely spread when reduviid bugs defecate in bites usually sustained while humans are asleep, it can also spread through contaminated food or blood, organ transplants, and pregnancy.

Chagas disease occurs in two stages: an acute stage, that develops one to two weeks after being bitten, and a chronic stage, that develops over many years. The acute stage can be symptom-free. Early symptoms, however, include fever, body aches, headaches, rash, vomiting, and fatigue. If caught in the acute stage, Chagas disease can be cured with benznidazole or nifurtimox.

Unfortunately, most chronic infections are asymptomatic. Therefore, many people who have Chagas are unaware of it until it’s too late for effective treatment. According to the Centers for Disease Control and Prevention (CDC), about 20% to 30% of people who’ve been infected develop more serious problems like digestive and nervous system symptoms, heart failure, stroke or death.

Most recent estimates suggest Chagas disease infects about 6-7 million people globally with 30,000 to 40,000 new infections per year, and about 10,000-12,000 deaths per year. Countries in Latin America are the most affected. Although it is considered a tropical disease, mounting evidence indicates Chagas disease has become an endemic disease in the U.S. (See, Christensen, J., “‘Kissing bug’ disease is here to stay in US, experts say. Here’s why it’s spreading,” CNN Health & Climate Unit, September 18, 2025.)

Scientists have found kissing bugs in 32 states (mostly Southern states), and have identified at least 17 states with infected mammals. Doctors have reported Chagas disease in eight states: Alabama, Arizona, California, Louisiana, Missouri, Mississippi, Tennessee, and Texas. In Florida, about 30% of kissing bugs appear to be infected. Now that it’s become more widely known that Chagas disease is endemic, the CDC has implemented increased surveillance and guidance.

New World Screwworm (NWS) Disease (Myiasis). Myiasis is a parasitic infection of fly larvae (maggots) in human tissue.  If you find appalling the idea of reduviid bugs defecating in wounds caused by their bites, then infestations of maggots in live human tissue will likely make your skin crawl.

The New World screwworm (NWS) is a species of parasitic fly that can cause myiasis when the larvae (maggots) feeds on live tissue. (In contrast, larvae of the green bottle fly, Lucilia sericata, are used clinically to debride dead tissue.)  NWS infestations begin when a female fly lays eggs in open wounds. Symptoms of NWS infestation include feeling maggots moving within a skin wound or sore in or around the ears, nose, eyes, or mouth. These wounds or sores are typically very painful. If you see or feel maggots in a wound, immediately ask your healthcare provider to remove them.

According to the CDC, NWS primarily affects livestock and is typically found in South America, Cuba, Haiti, and the Dominion Republic. A person traveling to these areas is at higher risk for NWS.

NWS was once a resident of the U.S.; it was officially eliminated in 1982. But as screwworms are very sensitive to climate and likely impacted by climate change, there is a risk of re-establishment in the U.S.

Cases have recently spread northward through Central America and Mexico. On September 22, 2025, NWS was confirmed in a cow just 70 miles south of the U.S.-Mexico border, and on August 27, 2025, the first human screwworm case was reported in the U.S. On September 30, 2025, the U.S. Food and Drug Administration conditionally approved the drug Dectomax-CA1 for the prevention and treatment of NWS larval infestations in cattle.

Given the infestations in livestock and other animals as well as in humans, and the concern that the disease is reemerging here due to climate change, the CDC is increasing its surveillance of NWS.

The way forward. Contrary to the opinion of the U.S. President, climate change is not “the greatest con job perpetrated on the world.” (President Trump’s speech to the U.N., September 20, 2025). It is real and, among other things, it’s profoundly impacting human health. As stated by The Climate Reality Project, “We need real science to inform efforts to protect the American people from this real threat—not denial.” It is time for all hands on deck. We must combat unwelcome climate migrants like the “kissing bug” and NSW by doing everything we can to ameliorate the impact of climate change on our planet. Our health, if not our very existence, depends on it.