Parasites and vectors: the original renegades

Triatomines and their trypanosomes are popping up in New Orleans, a beloved mecca of food, the arts, and music, reminding us that parasites and their vectors don’t play by our rules.

the World Health Organization and the Centers for Disease Control recently stated that SARS-COV2 is transmitted by aerosol droplets. We’ve known this critical little piece of information for over a year, but does this statement finally make it true?

In many ways the answer is yes. When something is OFFICIALLY ANNOUNCED, resources begin to flow to resolve the OFFICIAL PROBLEM. Of course, less with COVID-19, since it has turned into an enhanced pandemic. But for many other diseases, it is a real problem. Chagas disease, for example. Last month we celebrated a day designated by the World Health Organization to call attention to this widespread parasitic disease that affects millions of people in nearly every country in the Western Hemisphere.

Despite millions of people suffering from Chagas disease, a lifelong parasitic infection that can lead to heart failure, the disease is not well known in the United States because it is officially NOT TRANSMITTED HERE. Despite 112 years of research into the disease, there is no vaccine (and there is certainly no Operation Warp Speed ​​for a disease that IS NOT HERE). The parasite that causes Chagas disease, Trypanosoma cruzi, is transmitted in several ways, including through contact with the droppings of triatomine bugs. Like HIV, measles, and possibly COVID-19, Chagas disease is a zoonotic disease, which means we share it with animals.

Zoonotic diseases can pass from animals to humans and vice versa; they are a symbol of the intertwined nature of planetary and human health, and a symptom of the continued human destruction of non-human habitats. Chagas disease is particularly complex in that it is caused by a parasite, transmitted by an insect and harbored by mammals, including us. As a result, the disease is spread within and between many different landscapes – forests, villages and everything in between.

There are a lot of assumptions about where T. cruzi transmission occurs, and by what. Most of these assumptions are based on a lack of evidence, starting with Chagas disease being a rural disease of poverty. While, yes, Chagas disease is transmitted in rural areas, the disease is also found in urban areas. T. cruzi– infected kissbugs were found in cities across Latin America – São Paulo, Rio de Janeiro, Cochabamba, Arequipa, Caracas– and the list just keeps growing.

The second hypothesis is that kissing bedbugs is a problem “south of the border”. Triatomine studies in the United States are on the rise, and it’s not because the bugs have been walking here with immigrants from Central America, despite what some media would like to tell you. Insects have been there for millions of years. The point is, it wasn’t until now that people started to take an interest, which brings up a third principle from Chagas, although this one is generally true – if you are looking for triatoms, you will find them. Kissing insects in the United States began to gain a lot of attention as bomb-sniffer dogs deployed in Iraq began to show heart symptoms due to T. cruzi infection. Since Chagas disease is strictly transmitted in the Americas, attention was drawn to where the dogs had been trained – San Antonio, Texas. Naturally, the US government threw heaps of money at the problem. A series of follow-up investigations revealed four species of kissbugs living in and around military kennels in Texas, and dogs infected with T. cruzi have been found all over Texas. A slew of new kissing bug studies followed, which are still ongoing. This year alone, a study of 476 government working dogs in 40 US states found a T. cruzi seroprevalence of 12.2% (58/476). These studies continue to reveal that kissing insects are everywhere in human-dominated areas (that is, not just “natural areas”) of Texas and the United States. Ironically, 2009 was the 100e anniversary of the discovery of T. cruzi by Carlos Chagas in Minas Gerais, Brazil. I can’t help but wonder what all the money thrown at Chagas in military puppies could have done for the millions of people with Chagas disease in Latin America and the Caribbean.

Rodent map and prevalence of Trypanosoma cruzi in the neighborhoods of New Orleans. Figure of Ghersi and his colleagues research

But we’re not here to talk about US military spending, and we’re not here to talk about Texas. We’re here to talk about N’awlins, the city of jumblaya, jazz and… kisses? In a city where tourists flock to soak up its one-of-a-kind food, arts and culture scene, it’s especially interesting that recent studies reveal that apparently kissing insects and T. cruzi-infected mammals want to be there too. In their work recently published in Parasites and Vectors, Ghersi et al. found 11% of rodents positive for T. cruzi, including those sampled in tourist hot spots like the French Quarter. And only a few weeks before, Dumonteil et al. reported that 25% of shelter cats sampled in southern Louisiana were positive for T. cruzi. In another study, 45 insects collected from human homes and animal shelters were molecularly analyzed to determine the hosts the insects fed on, and they found that the insects opportunistically fed on a wide range of species, including birds, reptiles, amphibians and mammals, both domestic and synanthropic. To finish, another study found on 195 sequences of Triatoma sanguisuga collected in and around the human residences of the parish of Orleans (i.e. the county), human blood meals were found in 162 of them.

Most importantly, the predominant host species of bedbugs were humans and their animals. This discovery makes me think that another dogma of Chagas will be reversed, namely that the vectors T. cruzi transmission in the United States is strictly enzootic. I predict that better access to molecular tools allowing the identification of many blood meal host species, coupled simply with more bug-scouting people, will transform these dogmas of Chagas inheritance into an acceptance based on proofs. T. cruzi is transmitted to humans by kissing insects in the United States in multiple landscapes, including urban areas. No, it’s not that common, and no, there’s no need to panic. But, like i wrote before, these dogmas and labels of “it happens here but not here” and “to them but not to us” are not helpful. These labels serve as barriers to accessing resources and raising awareness among those who need to be sensitized (health professionals, people living in infected areas). As the global health community, we need to stop sticking these labels and categorizing them as “forever”, and start accepting that transmission is happening where it is happening. Maybe then we will learn to be light and one day maybe to react in time.

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