How Bullet Ant Stings Target the Nervous System To Inflict Maximum Pain

Ants may be small, but some species pack a powerful punch with their venom. Among these, the South American bullet ant (Paraponera clavata) is famous for delivering one of the most excruciating stings in the insect world.

Studying the venom of insect stings and unravelling how they cause intense pain is of great interest to toxicologists and entomologists alike. Still, years of previous study had not yet come up with a satisfactory explanation for why the ant’s sting is uniquely painful and long-lasting.

In a study published in Nature Communications, researchers from the University of Queensland cracked the code – discovering that the world’s most painful ant sting acts more like snake and scorpion venom.

How does the bullet ant sting cause pain?

Dr. Justin Schmidt, an American entomologist who created a pain index of stinging insects, rated the bullet ant sting as being the most painful insect sting in the world.

“Bullet ant stings can be painful for up to 12 hours and it’s a deep drilling pain you feel in your bones with sweating and goosebumps, quite unlike the 10-minute impact of a typical bee sting,” said lead study author Dr. Sam Robinson, a senior research fellow at the University of Queensland Institute for Molecular Bioscience.

The majority of ant species produce venom and are able to deliver a punchy sting if they feel threatened. However, the chemistry and pharmacology behind the ant sting has been relatively poorly explored in scientific literature, largely due to the small size of ants and the difficulty of obtaining samples of their venom. 

The science behind the sting

In their study, the University of Queensland scientists have shed light on the biochemical mechanism behind the pain caused by bullet ant stings. The study reveals that the venom contains peptide toxins that target nerve cells, specifically the sodium channels responsible for sending pain signals to the brain.

• Normally, these sodium channels open briefly to transmit pain signals, resulting in brief sensations of pain.
• Bullet ant venom contains specific toxins that can bind to these sodium channels and force them to stay open longer.
• This causes the continuous activation of nerve cells, leading to feelings of prolonged, intense pain.

“Normally, the sodium channels in these sensory neurons open only briefly in response to a stimulus. We discovered that the ant toxins bind to the sodium channels and cause them to open more easily and stay open and active, which translates to a long-lasting pain signal,” Robinson explained.

This action is similar to that found in the venoms of other animals. However, the ant venom toxins were found to be structurally and mechanistically distinct from other known sodium channel modulators found in the venom of scorpions, sea anemones and cone snails. This highlights the bullet ant’s venom position as a sophisticated biochemical weapon.

A bullet ant. Credit: Sam Robinson / Institute for Molecular Bioscience, University of Queensland.

What are the symptoms of a bullet ant sting?

Bullet ants use their sting offensively to paralyze their pray – normally other insects or small organisms – in addition to using it defensively to kill or ward off threats to their nest.

In humans, the bullet ant sting is notorious for being extremely painful and very long-lasting. It may also cause:

• Uncontrollable trembling
• Edema (swelling) at the site of the sting
• Temporary paralysis in the affected body part
• Tachycardia (elevated heart rate)
• Lymphadenopathy (swollen lymph nodes)

One of the most common questions is: Can a bullet ant kill you?

The straightforward answer is no. While the bullet ant sting is excruciatingly painful, it is generally not fatal to humans. Extreme cases – such as receiving hundreds of stings at once – could possibly result in death, however there are no confirmed reports of any human deaths resulting from bullet ant stings.

However, it is important to treat any sting properly and seek medical help if symptoms such as difficulty breathing, swelling of the face or throat, or dizziness occur, as these could indicate an allergic reaction.

Implications for pain research and medicine

Understanding how bullet ant venom manipulates sodium channels could help researchers develop new pain treatments.

The neurotoxins in ant venom represent a unique class of molecules distinct from other venomous animals’ sodium channel modulators, which could allow for unique insights on how pain signals are transmitted in the body. Such knowledge could inspire new directions for the development of novel analgesic medicines.

“We want to understand pain at a molecular level and toxins are fantastic tools to do this,” Robinson said. “These neurotoxins which target sodium channels are unique to ants, no one has found anything that looks or acts the same way so now we have a new set of tools to work with.”

 

Reference: Robinson SD, Deuis JR, Touchard A, et al. Ant venoms contain vertebrate-selective pain-causing sodium channel toxins. Nat Commun. 2023;14(1):2977. doi: 10.1038/s41467-023-38839-1

 

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