Intestinal Worms
Intestinal Worms
A significant percent of humans are infected with intestinal worms. This section introduces how worms impact our species.
Learning Objective: Explain how approximately one-third of humans have become infected with worms, including worm life cycles and impacts.
Approximately two billion people on Earth are infected with worms. The number is staggering. Clearly these worms are not typically lethal, or we would have heard of these numbers before. However, worms often reside in the intestines, stealing nutrients away from their human hosts. This section introduces parasitic worms and their impact on humans.
First, an introduction to the various worm taxa, including two that include worm species that parasitize humans.
Watch this video; you can select the closed captioning “cc” option if you would like to see the text.
Just to reiterate: most worm species are not harmful to humans, some species are beneficial like earthworms. These Planaria flatworms are commonly found in freshwater where they are omnivores and are eaten by larger carnivores. Those big eyespots detect light and are one of their most recognizable features. We keep them as pets.
Back to the parasites.
This video shows how humans become infected, how large the worms get, and their impact on the human population.
It’s time to see real worm specimens, including tapeworms and Ascaris roundworms
Note: some of these worms can be disturbing. If you have had a cat or dog with worms, you know what we are talking about.
The larvae of Ascaris roundworm can leave the intestines, travel though blood vessels in the lungs, move up the trachea (windpipe) and get swallowed, re-entering the intestines to grow into adults. All grotesqueness of this aside, the lung migratory stage is particularly dangerous for people who may already have lung damage from Tuberculosis (TB) and other diseases. Researchers have noted that there are fewer “lung migrators” in some populations of Ascaris.
A hypothesis is that intestinal worms are co-evolving with our species to become less deadly. The last thing intestinal worms need to do is kill their host where they feed, grow, and breed, releasing eggs with fecal material. Fewer lung migrating worms may improve worm fitness, and be less dangerous to humans.
Organisms can parasitize other parts of the human body, but it is the intestinal worms that impact the largest number of humans. Chemicals that damage the worms are also often hard on the human hosts.
Check your knowledge – Intestinal Worms
Review your notes. Do you understand the impact of intestinal worms on humans? If so, move forward to the next page.
Learning Objective:
Explain how approximately one-third of humans have become infected with worms, including worm life cycles and impacts.
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