Contributor: Meghan Hurley, MD
Educational Pearls:
What animal is the most lethal to humans?
Depending on how we define lethal, and animal, this answer is actually not straight forward.
Globally and in the U.S. the most lethal animal is humans, accounting for ~436,000 to ~20,000 deaths (homicides) per year on average respectively.
In the United States the most lethal animal is of the Hymenoptera order (bees, wasps, and hornets). It accounts for approximately ~60 deaths per year from anaphylaxis. Globally the number is harder to track, but is estimated between 250–3,800 deaths globally annually.
Globally the most lethal animal is venomous snakes, accounting for between 60,000-150,000 per year (whereas in the United States this number is closer to ~5).
Mosquitos, as a vector however for the pathogens they transmit, out rank all as the most lethal globally (excluding humans).
What are the key take-aways for each insect discussed in this episode?
Mosquitos:
In the United States, of lesser concern. Can potentially transmit West Nile Virus in the United States. Otherwise, treatment for general mosquito bites is topical antihistamines and over the counter steroid creams.
Hymenoptera order (bees, wasps, and hornets):
Distributed throughout the US, and can also live in the ground.
Bees lose their stinger during a sting. Whereas wasps do not and can sting multiple times.
Typically stings are just localized for symptoms (pain and swelling) but can become anaphylactic.
Treat with IM Epinephrine as the first line. Consider bronchodilators from bronchospasms.
Multiple stings (around ~100), can cause end organ damage and rhabdomyolysis outside of just anaphylaxis alone. Require more aggressive management.
Fire Ants:
Behave similar to bees (in swarm mentality), but have differing venoms. Can also cause global symptoms.
Black Widow:
No deaths from Latrodectus hesperus (Western Black Widow) recorded in the United States. There are 3 deaths globally from widow species. Two from Madagascar, and one from a Mediterranean species of widow.
Debate in the toxicology community about use of the antivenom, which may account for more deaths than the bite itself.
Black Widow bites are typically painful. Which is different from bites from recluse species.
Brown Recluse:
Rare in Colorado
Typically painless bite, that creates a center necrotic eschar.
Tend to also not be lethal.
Bed Bugs
Typically harmless and more of a nuisance to have. Can cause localized infections.
Bite presents in a "Breakfast, Lunch, and Dinner" formation (i.e. linear 2-3 or more bites as the bug tracks and feeds on skin).
Will feed primarily on exposed skin.
The biggest concern is ensuring no cross contamination from patient to provider or facility.
Bed bug bite delivers a small amount of local anesthetic, which can make them hard to detect.
References
Haskell MG, Langley RL. Animal-Encounter Fatalities, United States, 1999-2016: Cause of Death and Misreporting. Public Health Rep. 2020;135(6):831-841. doi:10.1177/0033354920953211
Herness J, Snyder MJ, Newman RS. Arthropod Bites and Stings. AFP. 2022;106(2):137-147.
GBD 2019 Snakebite Envenomation Collaborators. Global mortality of snakebite envenoming between 1990 and 2019. Nat Commun. 2022;13(1):6160. doi:10.1038/s41467-022-33627-9
Wei YL, Wu Z, Li RL, Tang F. Review of selected mosquito-borne diseases: arboviruses (dengue, chikungunya, Zika, West Nile, Japanese encephalitis, yellow fever) and parasitic diseases (malaria, lymphatic Filariasis). Front Public Health. 2025;13:1712094. doi:10.3389/fpubh.2025.1712094
Forsberg K, Sheats KJ, Blair JM, et al. Surveillance for Violent Deaths - National Violent Death Reporting System, 50 States, the District of Columbia, and Puerto Rico, 2022. MMWR Surveill Summ. 2025;74(5):1-42. doi:10.15585/mmwr.ss7405a1
Summarized by Dan Orbidan, OMS2 | Edited by Dan Orbidan & Ahmed Abdel-Hafiz, NREMT-P
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