Health Hanging in the Balance: The Curious Case of the Tightrope Walkers
The sun is setting behind a group of concrete buildings, and a layer of dust rises from the surrounding foot traffic. You are standing at the bus stop, when you look over and see a dimly lit figure, seemingly floating off the ground.
You squint and try to concentrate as the figure clears in your vision, and you see they are walking on a nearly invisible tightrope 12 feet above the ground, securely fastened to the eaves of two one-story shops.
Before having a minute to observe the parkour-savvy acrobat in front of you, yet another figure catches your eye balancing even higher than the first, silhouetted against the sky, walking on a broad, steel beam 40 feet off the ground between two tall commercial buildings.
Now, you are sufficiently bewildered, and your mind begins to wander. What is the story behind these two mysterious tightrope walkers? Both seem to be in some level of danger/risk of injury if they slip up even for a moment.
You wonder, “Who is at greater risk?”
Before you answer, let’s look at another area of risk that parallels this scenario.
Let’s compare walking on a tightrope to living in an area where there is some level of malaria prevalence.
Like a beam, or a thin tightrope, malaria exposure fluctuates in different countries and climates — the perceived risk of infection and any subsequent complications of malaria also varies within communities affected.
In these communities, a question lingers especially for those living in endemic areas: “Does malaria immunity exist?”
The short answer, is no, immunity to malaria does NOT exist, no matter how much exposure you have experienced.
However, NAI or naturally acquired immunity exists. NAI acts the way some might think of resistance.
After repeated exposure to multiple infections, an individual’s immune system becomes more accustomed to fighting the malaria parasite, consequently reducing parasite count in the blood for subsequent infections.
When the number of parasites is lower in your blood stream, the risk of death and other severe complications of malaria is lower (e.g. cerebral malaria).
Wait, so that’s a good thing right? So it would seem.
One might view this “acquired” resistance as a silver lining, especially for the population at large in a country like Rwanda which, aside from some few districts, experiences high exposure to malaria.
And, although mortality rates in Rwanda are now relatively low (under 1,000), morbidity rates and cases (4,794,778 in 2017*) are increasing, and everyone still remains at risk.
But there’s also another catch.
When an individual with NAI moves from a high malaria exposure area to a low exposure area, their NAI can wane over time, making them more vulnerable to severe malaria.
If NAI among adults becomes compromised in a country, the results can be catastrophic for select populations, not just for vulnerable populations such as children under five, pregnant women, and people living with HIV/AIDS.
But what about Rwanda’s Northern province where malaria exposure is low, how does that setting influence risk in a country that is otherwise endemic? Does malaria even exist in the Northern province? And should you be protecting yourself from malaria in an area of lower prevalence?
Malaria cases are lower in the North due to various environmental factors (including colder climate) that make the area hypoendemic, but malaria exists there nonetheless, and in some cases, can be even more dangerous.
A person’s risk of severe malaria is higher in an area that experiences a lower rate of infections.
In the same way high exposure areas increase levels of naturally acquired immunity (NAI), low exposure areas have the opposite effect.
“Where the risk of infection is low, almost all exposed people are at a substantial risk of debilitating or severe disease.” (Doolan)
Let’s go back to the tightrope/beam walkers at the bus stop and check in with them.
Let’s say the walkers represent individuals in Rwanda; and them falling represents their risk of contracting malaria, while the distance they might fall represents the severity of their symptoms.
This makes for an interesting thought experiment; if someone is at low risk of contracting malaria, but at high risk of having severe complications if infected, should they be more cautious than someone with a high risk of contracting malaria, but who is at low risk of severe complications if infected? As a bonus, let the person’s agility represent their NAI.
Should they both be cautious?
But wait a second…
What does caution even look like when trying to avoid a high risk of malaria? And what does it look like for these tightrope walkers?
The good news is no matter where malaria exists, female Anopheles mosquitoes (the malaria vector) are primarily active in taking blood meals after sundown. Use your mosquito net and tuck it in every night, close your windows at sundown, remove standing water where mosquitoes lay their eggs, and seek treatment if you notice malaria symptoms like fever, headache, or chills etc.
These behaviors are like handing the tightrope walker a set of stickier shoes with better traction.
As for the comparative risk for the tightrope walkers…
We leave the calculations up to you.
*“Rwanda saw more than an eight-fold increase in reported malaria cases, from 564,407 in 2012 to 4,794,778 in 2016.”(Rwanda: Malaria Operational Plan FY 2019)
Doolan, D. L., Dobaño, C., & Baird, J. K. (2009). Acquired immunity to malaria. Clinical microbiology reviews, 22(1), 13–36.
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