Have you heard of Chagas disease? The CDC estimates that 300,000 people in the United States are infected with it already – and don’t know it. Chagas disease is caused by a parasite that lives in the gut of the blood-sucking Kissing Bug (Triatoma gerstaeckeri). Kissing Bugs are especially common in south Texas. I found this horrifying specimen in my house just as I finished up this column! Robert Benson Photo.
If you have ever had a pet die, you know that it feels like you have lost a family member. When a beloved hunting dog dies, it feels like you have lost not only a family member but also your right arm.
So when our German Short-haired Pointer developed symptoms of heart failure, we were very sad. It was as though his heart could no longer pump well enough to keep his body fluids circulating. He became thin, weak, and bloated. He was nine years old, and we thought his condition must be due to old age. He was not getting any better, and we knew he had to be euthanized.
He has been gone for several months now. We will always miss him, and we deeply sympathize with anyone else losing a pet. Recently, our friend Mark Secord, was telling my husband the sad story of having to put down his own dog. Mark described the symptoms the dog had suffered from. We were shocked to realize that the illness was remarkably similar to that which killed our dog.
Mark went on to say that his vet suspected that the illness was Chagas disease. I was surprised to hear this. I had no idea that dogs could get Chagas disease. I thought it only affected humans, and that it mainly occurred in Latin America. And I was pretty sure it was caused by the bite of a nocturnal, blood-sucking insect, the Kissing Bug.
It was time to investigate. Wikipedia and the CDC website confirmed that the disease is caused by a parasite carried by the Kissing Bug. The parasite is Trypanosoma cruzi, and it lives in the gut of the Kissing Bug. When the bug bites a human, it subsequently defecates on the wound. As in most bugs’ bites, the skin around the wound is irritated and itchy. This makes the bitten person want to scratch. Scratching rubs the parasite-ridden feces into the person’s broken skin and subsequently into his blood stream. An infection can result.
Infections from T. cruzi usually follow two paths. The first infection causes fever, flu-like symptoms and localized swelling. And some people have no symptoms at all. After a few weeks, this acute infection subsides and that may be the end of it.
However, not always. Following the acute phase, a prolonged, long-term infection occurs. During this chronic phase, the parasite may not even be found in the blood. The person likely will have no symptoms. Most humans that have contracted the disease will not know it. This chronic stage can go on for years, even a lifetime. Unfortunately, an unlucky 20-30% of those infected develop the very serious symptoms of advanced Chagas disease.
And it is a killer. The CDC lists the complications of chronic Chagas disease as: “heart rhythm abnormalities that can lead to sudden death; a dilated heart that doesn’t pump blood well; and a dilated esophagus or colon, leading to difficulties with eating or passing stool.”
I researched what the parasite does to cause these symptoms. The parasite is a tiny animal called a protozoan. Once inside the body it enters living cells and replicates inside of them. It targets the cells of the autonomic nervous system, which is the part of the nervous system that controls involuntary muscles. These muscles are those that cause the heart to beat and the digestive system to move food along. By damaging the nerve cells controlling these organs, the muscles in them become flaccid. The problem gets worse for the longer the person has had Chagas disease. It is a slow, mostly silent killer. The person or animal infected with chronic Chagas usually dies of heart failure.
Like our dog did. Yes, Chagas affects about 150 mammal species, including domestic dogs. In the wild, the Kissing Bug lives around woodpiles and packrat nests. The rodents are a convenient source of the blood meals the Kissing Bug needs to survive. Unfortunately, many dog kennels (and some human homes) in south Texas are located very near to brush piles and woodrat middens. It doesn’t take a Kissing Bug long to take advantage of other mammals for its blood meals.
So, why is it called a “kissing bug?” Apparently, the bug is attracted to carbon dioxide exhalations and most often bites its victim on the face. Since Kissing Bugs feed at night, the victim doesn’t know it until the next morning. By then he (or it) has probably already scratched the bite. It is thought that dogs may even ingest the bugs.
Chagas disease is considered one of the neglected tropical diseases. However, in the last decade, it is getting far more attention. It is estimated that 300,000 people in the United States are infected with it already. And most of them don’t know it. Dr. Peter Hotez of the Baylor School of Medicine is looking into the many “anecdotal” cases of Chagas in Texas. He believes that it is much more common than previously suspected, especially in south Texas.
A research team at Texas A&M University has been investigating the presence of the T. cruzi parasite in Kissing Bugs and in wild and domestic mammals. A study of dogs at animal shelters in 2013 found that 8.8% of shelter dogs are infected.
Nevertheless, you need not to worry. You cannot contract the disease from mammals or other humans, only from the bite of Kissing Bugs. So avoid Kissing Bugs and you are safe from ever contracting Chagas disease. Actually, that is not true. Blood and organs from infected donors can transmit Chagas disease to recipients. And mother-to-fetus transmission is well known. Fortunately, blood donations have been screened for the presence of T. cruzi antibodies since 2007.
Even so, for the most part, avoiding any contact with Kissing Bugs is your best bet. Insect-proof your home and dog kennel. Use insect repellant while camping. Learn to recognize the four or five species of Kissing Bugs found in the US. Teach your children to recognize and not to handle Kissing Bugs.
As a naturalist and a citizen scientist, you can do more to help. You can carefully collect and submit Kissing Bugs to the Texas A&M Research Team. Just go to KissingBug@cvm.tamu.edu for instructions. By helping out with the submission of specimens of Kissing Bugs for testing for the parasite, we can all get a better understanding of the ecology and epidemiology of Chagas disease in south Texas.
OMG, it is 11PM and I have just found a live Kissing Bug in my kitchen. MY KITCHEN!!!! But I am going to be a true naturalist and citizen scientist. I have captured it, without touching it, in an old pill bottle. I am going to mail it to the Kissing Bug Research Program tomorrow. And now I need to go scrub my hands and kitchen walls with bleach.
ESSAY BY KAREN L. P. BENSON
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