HEALTH - Globalization and Disease: It's Always the Rats on the Ship

Wherever humans travel, we bring diseases with us and then leave them behind as parting gifts, often carrying new diseases back home in trade.

European colonizers infamously brought smallpox and other deadly diseases around the world with them (sometimes even using germs intentionally during warfare).

Europe itself was ravaged by the bubonic plague when humans provided transport to rodents and fleas from Asia, and that disease had a long history of hitching a ride with human travelers.

Asia and the Middle East had suffered multiple outbreaks before it arrived in Europe.

The global spread of disease has not stopped, despite efforts to mitigate the risk.

Air travel has introduced a new method of disease transport and mosquitoes on international flights have brought malaria to previously uninfected countries.

But just because airplanes provide a new way for diseases to spread doesn’t mean ships have lost their relevance when it comes to the global migration of diseases.

Rat lungworm disease is caused by a parasitic worm that, when introduced to humans, invades the human brain.

It is spread primarily through rats that travel on cargo ships.

Once in the brain, the parasite causes bleeding, swelling, and even death. ­­­­The worm is carried by rats, and also found in slugs and snails.

The disease was first recorded in humans in Taiwan in 1944, and it has been present in Asia and the Caribbean since then.

Recently, though, it’s become endemic in the United States, showing up in Hawai’i, California, Alabama, Louisiana, Florida, and along the Gulf Coast.

A 2013 study found that the geographical distribution of the disease had changed significantly over the course of a few decades.

There have been nine confirmed cases of rat lungworm disease in Hawai’i in 2017, as of April 12. There are also four suspected cases being explored currently.

These numbers may be low, though, because in other parts of the United States where the disease is present but less common, doctors may not be watching for it.

And, even if they were watching, there is no simple blood test.

Rat lungworm disease is not an epidemic, and may not become one in the near future.

Humans are not ­the target of the parasite, and when a human is infected it is just as catastrophic for the worm as it is for the human – there is not currently a way for the worm to get back out of the brain once it crosses the blood-brain barrier, and the parasite dies inside the human.

However, rat lungworm disease has proven itself to be highly adaptable, and a 2015 study found that the parasite was able to find new viable hosts that allow it to spread to new geographical locations.

Although Hawai’i has seen a significant spike in infections among humans, the numbers remain low.

However, the fact that the disease is continuing to spread and is proving to be persistent even in areas thought to lack a suitable environment for the parasite, is concerning.

Even if rat lungworm disease isn’t the next catastrophic epidemic, something will be.

Climate change, deforestation, global travel, economic instability and the ensuing civil unrest, and changes to funding from wealthy countries for health initiatives in impoverished countries are all contributing to a perfect storm for a global health crisis.

The next article in this series will examine these factors in more detail.

 About Tiffany Sostar

Tiffany is a published academic, an editor with the Editors Association of Canada, an independent scholar and researcher, and a self-care and narrative coach. She is particularly interested in the intersection of technology and identity - how our tools shape our selves and change our stories, and in how the nature of work is changing as we incorporate more technology into our daily lives.