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PRI's Environmental News Magazine

"Tropical" Diseases Reappearing in the U.S.

Air Date: Week of September 4, 2015

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The parasite Trypanosoma cruzi, which causes Chagas disease, can wreak havoc on heart muscle; consequently, Chagas disease is the leading cause of heart failure in Latin America. (Photo: Marc Perkins, CC BY-NC 2.0)

Tropical diseases such as Chagas disease, dengue fever, usually found in South America, Africa and Asia, are increasingly affecting people in the US, with debilitating and even deadly consequences. Journalist Carrie Arnold tells Host Steve Curwood how complacency and a lack of research have allowed these diseases to spread in the U.S., especially among poor people in The South.

Transcript

CURWOOD: It's Living on Earth. I'm Steve Curwood. Chagas disease, dengue fever, malaria...these are so-called “tropical” diseases, prevalent in Latin America, Asia and Africa. But cases of seemingly foreign infectious diseases in the American South are raising questions about the threat they can pose to public health. Joining us is Carrie Arnold, a science writer whose article on tropical diseases in the south recently appeared in the online magazine Mosaic. Carrie, welcome to Living on Earth.

ARNOLD: Thanks for having me.

CURWOOD: What diseases are we talking about here, and tell me why they're serious.

ARNOLD: So some of the diseases we're talking about are Chagas disease, which is spread by an insect known as the kissing bug. The kissing bug bites you and over time the Chagas parasite replicates in your body and especially in your heart muscle, and in about a third of cases the parasite eats away at your heart muscle over a period of decades, and so sometimes the only sign that you've been infected with Chagas disease is when you start entering heart failure.


The “kissing bug,” so-called because it bites near the mouth while a person is sleeping, can carry Trypanosoma cruzi. This parasite can infect a human host when he or she scratches the bite. (Photo: Dr. Erwin Huebner, Wikimedia Commons)

CURWOOD: That's horrible.

ARNOLD: It's really scary. And another serious disease is Dengue, which has also been nicknamed "breakbone fever" because it causes such severe joint pain. It's typically transmitted by mosquitoes, and in a very small number of cases it can also cause hemorrhagic fever, abnormal bleeding, but that's fairly rare. Mostly people just have severe joint pain and are incapacitated for several weeks, and there's also neurocysticercosis, which is a worm, and it's typically associated with improper handling or cooking of pork, and in some cases it can infect the brain. The worm can live for about 10, 15, 20, 30 years and it typically doesn't cause symptoms until the worm dies and then the body realizes that it has this foreign entity in the brain and that's when it causes a lot of symptoms like headaches, nausea, dizziness and seizures.

CURWOOD: One of the most interesting points of your article is that the incidence of these diseases in the United States is quite a bit higher than what people think. Why is so little attention being paid to these diseases?

ARNOLD: I think the main reason is that they’re diseases of poverty, and the diseases that get a lot of attention are the ones that tend to make each your average watcher of CNN or MSNBC or Fox news scared. It's things like Ebola, but since these are diseases associated with poverty, they tend not to scare us as much. They don't cause these big disastrous outbreaks, they're just constantly lurking in the background. We've assumed that they are typically diseases of somewhere else, and we really have no idea that they're even here, let alone what kind of disease burden that they're causing.


Dengue fever is a viral disease transmitted by mosquitos. It can be fatal if symptoms are not treated. About half of the world’s population is at risk. (Photo: James Gathany, CC BY-NC-ND 2.0)

CURWOOD: So talk to me about why something like Chagas is concentrated in the community of poor people.

ARNOLD: For vector-borne diseases, diseases that are transmitted by insects, things like Chagas disease and Dengue, a lot of it is associated with housing quality. You know so you have to have money to have screens on your windows? Do you have money to make sure the screens don't have holes? Do you have money to have air conditioning and keep your windows closed? Do you have the money to repair cracks in the wall that might let insects in? Another factor is just things in the environment. Standing water... is your neighborhood prioritized for insect spraying? You know you have these so-called tropical diseases and you know they tend to be really chronic, they're not as acute like the flu where you get sick for a week and then you get better. They tend to persist for a really long time and they sap your ability to work and to think properly, and so it creates this vicious cycle of poverty.


The larvae of the pork tapeworm can cause cysts to develop in the brain, leading to neurocysticercosis. Symptoms include epilepsy, severe headaches, and blindness. (Photo: CDC, CC government work)

CURWOOD: What's the role of race in tropical disease rates here in the United States?

ARNOLD: I think race is mainly an issue due to its strong association with poverty, and it also I think plays into the fact of why these diseases are so ignored by policymakers, by legislators who fund research.

CURWOOD: What about immigration? Any relationship between that and this unnoticed uptick in these tropical diseases?

ARNOLD: It's certainly a factor. I think the movement of people whether through immigration or travel is definitely increasing, but as much as Chagas disease is seen in immigrants from Latin America, it's definitely a major problem in that population, there's also transmission occurring in the United States itself. So it would definitely be wrong to blame it on immigration and to say it's only a disease of immigrants.


Chagas disease and dengue fever are correlated with poverty, in part because people lack the financial means to put physical barriers between themselves and disease-carrying vectors. The inability to fix broken window screens is one such problem. (Photo: Sharon Morrow, CC BY-NC-ND 2.0)

CURWOOD: In your article you say that research on tropical diseases in the American South petered out half-century ago. Why?

ARNOLD: Part of it was due to, I think, a global decrease in research in these diseases. By the 1960s, with a lot of the new antibiotics and the development of some new anti-parasitic medications, it was really generally thought that these diseases would become a thing of the past. And so researchers, scientists, physicians, were really discouraged from going into this area of research because it was seen as an area without a future. All too soon we learned that that thinking was really inaccurate, you know, infectious diseases are still a major problem and a lot of the methods used to diagnose these parasitic diseases are the same that were used in the 1950s and 60s; whereas if you look at diagnosing other diseases like the flu, I mean, you have rapid tests, you have DNA or RNA tests, with parasitic diseases you're still looking under a microscope and counting eggs.


Carrie Arnold is a freelance science writer who previously worked in the field of public health. (Photo: courtesy of Carrie Arnold)

CURWOOD: So we count on medical advances in this society - vaccines, special treatments - how likely is it that such advances can effectively thwart these tropical diseases that have emerged and reemerged in the south?

ARNOLD: I think there are a lot of advances in the pipeline. Part of the difficulty is that developing a vaccine against a parasite is a lot more complicated because their biology is a lot more complicated than a virus or a bacterium, and there isn't nearly the profits to be made in treating diseases like Chagas or neurocysticercosis as there is in treating diseases like influenza. That being said, there's been some really good public/private partnerships—efforts that have a combination of government funding nonprofit funding and even some smaller pharmaceutical funding--to develop these types of tests and vaccines.

CURWOOD: So how should we protect ourselves at risk of contracting these horrible tropical diseases here in the US?

ARNOLD: I think a lot of it needs to start with better research and better epidemiology. And another major factor is just working to decrease poverty. Decreasing poverty should for a lot of these diseases also help decrease transmission.

CURWOOD: Carrie Arnold is a freelance science writer working in the field of public health. Thanks for taking the time with us today.

ARNOLD: Thanks for having me I really appreciate it.

 

Links

Arnold’s “Can America cope with a resurgence of tropical disease?”

Chagas Disease

Dengue Fever

Neurocysticercosis

About science writer Carrie Arnold

 

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