The Kiss of Death

“We slept in the village, it is a small place, 5 leagues South of Mendoza, & is the S. limit of the fertile territory of that Province. At night I experienced an attack, & it deserves no less a name, of the Benchuca, the great black bug of the Pampas.1 It is most disgusting to feel soft wingless insects, about an inch long, crawling over ones body; before sucking they are quite thin, but afterwards round & bloated with blood, & in this state they are easily squashed. They are also found in the Northern part of Chili & in Peru: one which I caught at Iquiqui2 was very empty; being placed on the table & though surrounded by people, if a finger was presented, its sucker was withdrawn, & the bold insect began to draw blood. It was curious to watch the change in the size of the insect’s body in less than ten minutes. There was no pain felt. — This one meal kept the insect fat for four months; In a fortnight, however, it was ready, if allowed, to suck more blood.”  

         Charles Darwin’s Beagle Diary

There are many scholars today who believe that Charles Darwin contracted Chagas’ disease from his multiple encounters with the Triatomine species, also known as the kissing bug and the assassin bug. Most individuals in Central and South America are familiar with this bug that invades homes in the middle of the night for a quick drink of blood. 

More than 10 million infected people can attest to this bug’s destructive bite. Every year approximately 14, 000 people die from the complication associated with a bite from an infected Triatomine. What exactly is going on with this nasty little bug? As early as the 1909, researchers concluded that the Triatomine species were infected with a debilitating and potentially deadly protozoan called Trypanosoma cruzi

triatomine_map_smMost citizens south of our border avoid the kissing bug, for it is the vector that enables humans and other animals (dogs, cats, rodents, etc.) to get this awful little parasite. Unfortunately, the kissing bug is also here in the North American region. The CDC has documented 300,000 cases of this disease in the United States. According the World Health Organization, most of the cases were contracted before entering the country, but a few have been contracted while in the southern parts of the United States.

But don’t think you are safe from this infection. Researchers are conducting studies across the southern region of the United States. One study centered around El Paso, Texas, found 61 percent of the 39 Triatomine rubida tested positive for the T. cruzi parasite. “It surprised me that so many of them were carrying the parasite. I was expecting to have some, but this is quite high,” study leader Rosa Maldonado, an associate professor of biological sciences at UTEP, said in a university news release. “Doctors usually don’t consider Chagas disease when they diagnose patients, so they need to be aware of its prevalence here.”

The number one health problem in Texas, heart disease. Symptoms associated with chronic Chagas’ disease are heart rhythm abnormalities, inflammation of the heart and dilated esophagus or colon. About 30% of people infected with T. cruzi develop these severe symptoms. The rest of the infected population will have only mild or no symptoms until their immune system is weakened and/or the parasite can take advantage of a suppressed immune response.

Emerging infectious disease? Dr. Maldonado thinks so, and is asking physicians to start testing for the presence of the T. cruzi parasite in patients exhibiting symptoms of this infection, espeically in the southern regions of the United States.

She’s not alone. The American Red Cross thought this was a significant enough problem that they started screening all blood donors for the parasite beginning in 2006. 

Even the CDC considers Chagas’ disease to be one of the most neglected parasitic infections (NPI), a group of parasitic disease that has been targeted by the agency for public health action in the United States.

Thankfully, Dr. Maldonado isn’t the only researcher looking into this problem. Dr. Edward J. Wozniak, researcher at the University of Texas School of Public Health, began surveying across communities in Texas in 2010, looking for the distribution and rate of infection of the Triatomine with T. cruzi. He collected 542 specimens at 40 different sites over a three-year span.

The highest population of the Triatomine were associated with rural communities and areas close to natural undisturbed sites. What is disturbing, 64.4% tested positive for the T. cruzi parasite. 

According to Dr. Edward J. Wozniak, “The high rate of T. cruzi infection in our native triatomines once again documents that Chagas’ disease is endemic to south central Texas and suggests that the risk of human exposure to T. cruzi may be higher than previously thought. Because of this, Chagas’ disease should be considered on the list of differential diagnoses for cases of cardiac arrhythmia and heart failure in both humans and domestic animals from south-central Texas.”  

Studies in Arizona date back to 1964, when the rate of infection in the Triatomine was 7.5% (Triatoma rubida) to 19.5% (Triatoma protracta). Most of the Triatomine were associated with pack rat colonies, but with humans encroaching on natural habitat and the infection rate in kissing bugs climbing to 41.5%, the potential for people becoming infected with Chagas’ disease could be more likely than previously thought. 

To make matters worse, the United States is experiencing longer and warmer summers. The perfect environment for the kissing bug to breed and multiple. According to the American Association of Poison Control Centers, Arizona is experiencing the highest rate of human to Triatomine contact, and since Triatomine take advantage of any available blood bank, humans are likely to be on the menu.

A bite from the Triatomine isn’t the only way to become infected with Chagas’ disease. The disease can spread from an infected person through an organ transplant and through blood transfusions. Pregnant mothers can also pass the infection to their unborn child, and to make matters worse, researchers have found that food and beverages contaminated with “kissing bug” feces can also spread the disease.

So why haven’t we heard much about this disease? Due to our well insulated homes, Triatomine have little chance of getting inside your home to feed. Unless you keep your windows open and without screens, your odds of them getting inside are low.

The second reason, there isn’t many in the medical community testing for this disease. The disease isn’t “on the radar” right now, and some people may not show serious signs of infection for up to 20 years.

Lastly, researchers believe the feeding habits of the endemic species could be different from the Triatomine south of the border. Most of the Triatomine species in the United States feed predominantly on wildlife; pack rats, raccoons, and rodents. Their feeding behavior may also be different. Some Triatomine defecate while feeding, and spread the T. Cruzi from their feces into the wound. Females tend to exhibit this behavior more often than males and immature Triatomine, and some studies have shown that the local species tend to defecate after leaving the host.

With 300,000 people in the United States infected, I think maybe it’s about time we took a closer look at this nasty little parasite.

More information: CDC, University of Arizona