Putting the Science in Arthropod Borne Disease

Aedes aegypti (US Department of Health and Human Services)

The slam of a screen door—a quintessential part of summertime in the United States.

But not here in New Zealand. Most houses have no screens in windows or doors.

Why? Because we don’t have arthropod-borne diseases (of humans) here.

The ubiquitous window screens and screen doors in the US are a direct result of the efforts to eliminate malaria in the early 1900s. In some areas, screens were mandated by local government. They caught on, even in areas where they weren’t required, and remain popular today, in spite of the fact malaria is no longer endemic to the United States.

Lone Star Tick–transmits ehrlichiosis and a carbohydrate that can trigger meat allergies. (Centers for Disease Control and Prevention, Dr. Amanda Loftis,  Dr. William Nicholson, Dr. Will Reeves, Dr. Chris Paddock)

Arthropod-borne diseases have shaped human cultures, changed the course of wars, and stymied economic development throughout the world for millennia. Malaria alone kills 400,000 people annually, and hundreds of millions of people worldwide suffer from other arthropod-borne diseases like Chagas disease, yellow fever, dengue and leshmaniasis.

Arthropod-borne diseases are transmitted from one person to another by, you guessed it, an arthropod—often a mosquito, fly, or tick. These arthropods (just the females, in the case of mosquitoes) feed on human blood. They draw up the disease from a sick person with one meal, and transmit it to another person with the next. The disease—a virus, protozoan, plasmodium, flatworm, or other organism—often has a complex life cycle, requiring specific hosts and specific vectors in order to complete each stage of its life. Combating these diseases requires an understanding of every part of the life cycle of both the disease and the vector.

Though humans have been battling malaria for the entirety of recorded history, new arthropod-borne diseases emerge regularly, challenging public-health systems worldwide. With increased air travel, infected people and vectors can quickly spread diseases to new places. And diseases don’t necessarily act the same when transplanted into a different population.

Zika is a great example of the complex interactions between host, vector and disease that make arthropod-borne diseases so scary and difficult to combat. Zika was first identified in humans in 1952, after first being found in monkeys. It was confined to Africa and Asia until 2007. Only 14 cases were documented, though testing indicated people had wide exposure to the virus. Symptoms were usually mild, and it wasn’t considered a major problem.

The first large Zika outbreak occurred on the island of Yap in Micronesia in 2007. Further outbreaks in the Pacific Islands in 2013 and 2014 brought the first information connecting Zika with congenital malformations like microcephaly and severe neurological complications.

Then, in March 2015, Zika appeared in Brazil. Because Zika was unknown in Brazil, the outbreak wasn’t identified as Zika until May. In October, Brazilian health officials reported a dramatic increase in microcephaly, which was linked to the Zika outbreak.

By the end of 2015, Zika outbreaks had been reported all over Central and South America.

In February 2016, the World Health Organization declared Zika a Public Health Emergency of International Concern. Emergency plans were enacted to control the spread of the virus by eliminating the suspected vector mosquitoes, Aedes aegypti, and to study how to manage the complications of the disease.

The disease and our understanding of it moved rapidly throughout 2016. The virus was found in another species of mosquito. It was proven to also be transmitted through sex and through blood transfusions. It was discovered to cause a much wider range of neurological problems than first thought. Vaccine development began. Travel advisories were put in place. Innovative new mosquito control strategies were launched.

Still, Zika spread and infected over 180,000 people. By November 2016, it was clear Zika was here to stay, and needed to be managed on an ongoing basis, not as an emergency. In the space of 18 months, Zika had invaded the world.

The full timeline of Zika can be found on the WHO’s website: http://www.who.int/emergencies/zika-virus/history/en/

The WHO also has great information about other arthropod-borne diseases: http://www.who.int/campaigns/world-health-day/2014/vector-borne-diseases/en/

All the real-life science of arthropod-borne disease can make for exciting fiction. Fancy writing a story? Here are a couple of ideas to get you going:

1. A cluster of people in a small town in Iowa fall ill with an unusual rash that progresses to a deadly autoimmune disease. Doctors are stymied until one of the women mentions she’s just returned from a trip to Africa. Blood tests confirm she is carrying antibodies to a rare arthropod-borne disease not seen outside of Sub-Saharan Africa before.

  • How do researchers try to contain the disease? The first step is usually to quarantine sick people and those who have come into contact with them, but if this fails, control has to turn to other ways of breaking the disease cycle. Strategies may include vaccines, preventive medicine, killing the disease vectors, eliminating the vectors’ habitat, and separating people from the vector (with screens, curfews, etc).
  • Is there a competent vector for the disease in Iowa? In its native range, the disease may be vectored by an arthropod not found in North America, but some widespread arthropods are capable of vectoring many diseases. Arthropods within the same genus of the original vector are most likely to be able to transmit the new virus.
  • How does the progression of the disease in Iowa differ from in Africa, where people have been exposed to the disease for longer, and have developed a measure of immunity. Mild diseases can become deadly in populations never exposed to them before.
  • How does society as a whole react to disease survivors? The social impact of emerging diseases can be as devastating as the disease itself—survivors may still be sources of infection, and some arthropod-borne diseases can also be spread through other means (sexually, in feces or saliva, etc). How does this affect those who survive?

2. A government wants to unleash a new arthropod-borne virus to wipe out a rival nation (Don’t laugh, Japan tried to do this during WWII, breeding up disease in prisoners of war and releasing cholera-infected flies and plague-infested fleas in China, killing more people than the atomic bombs on Hiroshima and Nagasaki).

  • How will they choose a vector and disease to minimise the danger to their own people? Will they vaccinate their own people first? Or chose a disease already present in their country, but not in the target country?
  • How will they deliver live, infected vectors to the intended target?
  • How will they produce enough of the disease organism to infect the vectors?

And don’t forget to get yourself a copy of Putting the Science in Fiction, to be released on October 16! This is a great resource you don’t want to miss!

Science and technology have starring roles in a wide range of genres–science fiction, fantasy, thriller, mystery, and more. Unfortunately, many depictions of technical subjects in literature, film, and television are pure fiction. A basic understanding of biology, physics, engineering, and medicine will help you create more realistic stories that satisfy discerning readers.

This book brings together scientists, physicians, engineers, and other experts to help you:

  • Understand the basic principles of science, technology, and medicine that are frequently featured in fiction.
  • Avoid common pitfalls and misconceptions to ensure technical accuracy.
  • Write realistic and compelling scientific elements that will captivate readers.
  • Brainstorm and develop new science- and technology-based story ideas.
  • Whether writing about mutant monsters, rogue viruses, giant spaceships, or even murders and espionage, Putting the Science in Fiction will have something to help every writer craft better fiction.

Putting the Science in Fiction collects articles from “Science in Sci-fi, Fact in Fantasy,” Dan Koboldt’s popular blog series for authors and fans of speculative fiction (dankoboldt.com/science-in-scifi). Each article discusses an element of sci-fi or fantasy with an expert in that field. Scientists, engineers, medical professionals, and others share their insights in order to debunk the myths, correct the misconceptions, and offer advice on getting the details right.

Go in the draw to win a FREE copy of Putting the Science in Fiction