I love the concept of One Health, which emphasizes the interwoven nature of the environment, animals, and humans, where a change to one aspect of the world will affect the other surrounding environments and populations. This is a vital concept when it comes to global health, as we often focus on human disparities without working to improve the person's environment for sustainable health and change. As you can imagine, One Health is a critical component when describing the lifecycles of zoonotic diseases, which infect both animals and humans. I wrote a magazine article for The Biochemist about the impacts of One Health on disease emergence. You can find that here (e-zine) or here (PDF), for free.
Within the One Health symposium, each speaker outlined an important animal exposure for each infection, whether parasitic, viral, or bacterial. For example, the first speaker discussed an outbreak of hantavirus in Peru during the creation of a new interoceanic highway that runs across Peru and Brazil. Deforestation and construction created a new opportunity for exposure to hantavirus for construction workers and residents in the area. Here's some more info on that, if you are interested.
|Image of bats emerging from the Swedagon Pagoda in Myanmar, borrowed from an article on Biodiversity via ResearchGate|
The two talks that I really enjoyed covered parasitic infections that are a global issue affecting primarily low income populations, even those in the United States.
|Beautiful illustration borrowed from The New Yorker|
|An apple snail, image borrowed from Hidden History|
The apple snail can be purchased to eat from stands along the road in Laos, Cambodia, and Thailand, or the larvae can infest other aquatic animals. Once ingested by a human, the nematode travels to the brain through the blood stream, and then dies shortly after. The presence of a foreign body in the central nervous system causes a flood of white blood cells, specifically eosinophils, which triggers inflammation of the meninges. While this can clear on its own, some people have been seen with significant neurological dysfunction, some of which are lifelong, or death. This parasite is most commonly associated with Southeast Asia, in the past few years, has popped up in Hawaii.
Another speaker detailed a project focusing on parasitic load in public parks throughout New York. Toxocara spp. can infect dogs (Toxocara canis) and cats (Toxocara cati), and can also infect humans if the eggs are ingested. I think a lot of people in the US believe that parasites are a problem in other countries, but there are many types of parasites that can infect (and infest) people in urban and rural areas of the US.
|Toxocara roundworm image from the CDC|
This particular project tested soil and sand samples from parks because children are frequently exposed by ingesting soil and sand from parks, and from putting contaminated hands in their mouths. Infection during childhood can affect childhood development, and most people are never diagnosed if they don't present with severe symptoms. Many psychological symptoms aren't linked to parasitic infection, so they aren't treated appropriately!
|Some random kid from the internet eating dirt.|
The presenter's data, combined with the CDC's estimates of exposure in the US, suggests that a majority of those exposed to Toxocara are from disadvantaged communities, where public health initiatives fall short. This means that health services are not doing their jobs to protect all people within a community. We can't just protect select groups. All people have a right to be informed of what they may be exposed to in their local environment, and what local organizations (whether nonprofits, government organizations, or research initiatives) are doing to minimize risk!
If you are interested in this specific project, here is an older youtube video of the speaker describing her research:
Its important to remember that the concept of global health affects people around the globe, especially children, no matter where they live or how developed their environment is. Public health interventions have helped reduce the number of diseases that many people in developing countries would be exposed to, but no one lives in a sterile environment!