Chagas disease: The “kissing bug” disease spreading in the US

Chagas disease (American trypanosomiasis) is caused by the protozoan parasite Trypanosoma cruzi or T.cruzi.

The World Health Organization (WHO) estimates that  Approximately 300,000 people in the United States alone have Chagas disease, although fewer than 2% know they’re infected.

How does Chagas disease spread?

Transmission occurs primarily through triatomine insects. These insects have cone-shaped heads, a large flat body, and orange or red markings on the sides of their belly.

Triatomine insects are also called “kissing bugs” because they often bite people on the face or around the mouth while they sleep, though they can bite anywhere on exposed skin.

When the insects bite humans, they also defecate near the bite sites. The protozoan parasite that causes Chagas disease enters the bloodstream through insect feces.

Other routes include blood transfusion, organ transplant, ingestion of contaminated food or drinks, and congenital transmission from mother to child.

Congenital transmission occurs in about 4–5% of infants born to infected mothers. Most infected newborns appear healthy at birth, but some may develop serious complications such as

• Low birth weight
• Enlarged liver or spleen
• Cardiac inflammation

Historically, in the US and Europe, most infections were imported through migration. However, recent evidence and case reports indicate that Chagas disease is now spreading in southern and central USA.

Kissing bugs have been identified in 32 states, from California to Maryland. Infected mammals have been documented in at least 17 states.

Human cases acquired locally have been reported in 8 states: California, Arizona, Texas, Tennessee, Louisiana, Missouri, Mississippi, and Arkansas. Texas alone documented 50 locally acquired cases between 2013 and 2023, with cases occurring consistently each year.

In the southeastern US, researchers recently found that one-third of local kissing bugs (Triatoma sanguisuga) carried Trypanosoma cruzi, and nearly a quarter of those bugs had bitten humans.

Early detection is critical, since treatment during infancy is highly effective in clearing the infection.

Chagas disease has two distinct phases: acute and chronic.

The acute phase begins soon after infection and may last several weeks to a few months, often up to four months. In most cases, this stage is silent, with few or no noticeable signs. When symptoms do appear, they are usually mild and nonspecific.

After this period, the infection enters a chronic phase that can last for years or even decades.

Many infected people remain asymptomatic in the chronic stage, but a substantial proportion eventually develop serious complications, especially affecting the heart and digestive system.

Acute Chagas disease symptoms

When symptoms do occur during the acute Chagas phase, they typically resemble a flu-like illness.

• Fever, often high and prolonged
• Swollen lymph nodes, particularly in the neck or groin
• Fatigue and weakness
• Chills and night sweats
• Muscle aches and headache
• Facial or eyelid swelling (Romana’s sign)
• Other signs may include rash, loss of appetite, or breathing difficulty

Chronic Chagas disease symptoms

The chronic Chagas phase primarily affects the cardiovascular and gastrointestinal systems with potentially life-threatening consequences.

• Heart disease, including cardiomyopathy, arrhythmias, and heart failure
• Digestive problems, such as
  • Difficulty swallowing (megaesophagus)
  • Severe constipation/obstruction (megacolon)
• Neurological complications from nerve involvement
• Risk of sudden death from malignant cardiac arrhythmias

Because acute Chagas disease often looks like a common viral illness, recognizing when to investigate further is important.

People with persistent fever, fatigue, or swelling that doesn’t respond to over-the-counter medication should seek medical evaluation, especially if they live in or have visited areas where triatomine bugs are found.

A history of an insect bite followed by facial or eyelid swelling (Romana’s sign) is distinctive and should raise suspicion.

For clinicians, unexplained heart rhythm problems, enlarged heart, or gastrointestinal symptoms in people from endemic areas or in regions where triatomines are present should also prompt testing for Chagas disease.

• Serology (blood tests): Two distinct antibody tests (e.g., ELISA, IFA) are recommended to confirm infection
• Microscopy: Microscopy using blood smear or concentration techniques can detect parasites during acute infection
• PCR testing: Molecular methods detect parasite DNA, especially useful in congenital and acute cases
• Cardiac imaging: ECG and echocardiogram identify complications in chronic cases
• Newborn screening: Infants born to infected mothers should undergo parasitological and serological testing

Chagas disease is a serious health concern. However, advances in research and public health programs provide reasons for optimism.

Screening of blood donors and pregnant women has already reduced transmission in many regions. Experimental studies are exploring new drug regimens and vaccine candidates.

The current recommended treatment protocol includes antiparasitic drugs and management of side effects. Supportive care is recommended in the chronic phase.

• Antiparasitic therapy: Benznidazole and nifurtimox remain the only available antiparasitic drugs
• Effectiveness: Best outcomes occur in acute and congenital infections, where cure rates are high
• Chronic disease: Treatment may slow progression, especially in younger adults and those with early cardiac involvement
• Adverse events: Side effects are common (skin reactions, digestive upset, neuropathy)
• Supportive care: Manage cardiac and gastrointestinal complications according to standard clinical practice

While Chagas disease presents serious health risks, several proven strategies can significantly reduce transmission.

Prevention efforts focus on controlling kissing bug exposure, screening blood supplies, and identifying at-risk individuals before complications develop.

• Vector control: Housing improvement and insecticide spraying reduce bug exposure in endemic regions
• Blood and organ donor screening: Donor screening through universal testing in the US and Europe prevents transfusion or transplant transmission
• Universal testing: In the US and Europe, screening all blood and organ donors prevents transfusion or transplant transmission
• Maternal screening: Pregnant women from endemic regions should be tested to prevent missed congenital cases
• Food precautions: Avoid consuming unpasteurized juices or foods that may be contaminated with triatomines in endemic areas
• Travel medicine: Clinicians should be alert to possible infections in immigrants, travelers, or people living in US regions where triatomines are established

Chagas disease has long been considered a problem in rural Latin America. However, recent case reports and insect studies confirm local transmission in the United States, making it an emerging domestic health concern.

Doctors in both affected and unaffected areas should consider Chagas disease in people with unexplained heart or digestive problems, as well as in blood donors, pregnant women, and at-risk newborns.

Early diagnosis and prompt treatment with antiparasitic medications are essential. Prevention strategies, including screening blood and organ donors and raising awareness about kissing bugs, are crucial to reducing the impact of this disease.

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