Table of contents:
Video: How Worms Adapted To Spreading Eggs
How worms adapted to spreading eggs
- 1 Ascaris and pinworms - life without changing owners
- 2 The Great Journey of Trematode Larvae
- 3 Cestodes - the scourge of beef farming
The World Health Organization believes that every second person in the world at least once in their life has been infected with worms, or helminths. These parasitic worms enter the body in the form of eggs or larvae and remain forever in the host's body. To protect yourself from them, you need to know how the eggs of the worms enter the environment, how they spread in it and are populated into a new organism.
Ascaris and pinworms - life without changing owners
Human helminths belong to two zoological types: roundworms and flatworms. In roundworms, or nematodes, the life cycle often occurs without a change of host. Each of their new generation strikes a person.
Most of the eggs will eventually die, but some on the flies' legs will be transferred to food or dishes, which will be an infection factor.
Small pinworm nematodes produce an order of magnitude fewer eggs, but they use a more guaranteed way of delivering them to the host. The eggs of these worms enter the environment in the following way: the fertilized female crawls out of the intestine through the anus and lays in small folds of the skin of the anus. The itching that occurs during this makes a person scratch the perineum, the eggs move under the nails and, in the absence of necessary hygiene, into the mouth.
The Great Journey of Trematode Larvae
Many parasitic worms require a lot of oxygen in the early stages of development. In addition, hundreds of millions of years ago, when birds and mammals did not yet exist, they lived in the organisms of mollusks, crustaceans and fish. Since that time, stages have remained in their life cycle when the larva lives in one animal, and the adult worm in another.
Typical representatives of such helminths are trematodes, or flukes. For example, the adult stage of the liver fluke - marita - settles in the liver ducts of humans and herbivores. Here she is able to live for several years, feeding on the surrounding tissues. Marita is a hermaphrodite and fertilizes herself. Eggs descend along with bile into the intestines, pass through it and go out with feces.
When the eggs of the worms enter the environment, they are not yet ready to infect another person. They need to be in a reservoir, where a larva will hatch from them, equipped with many cilia. With their help, the larva actively swims in search of a specific mollusk - a small pond snail. Having found a mollusk by smell, the larva is drilled into its body and migrates to the digestive glands.
Feeding on pond snail cells, the larva actively reproduces by parthenogenesis - without fertilization. Some of her descendants are born with a new swimming device - a tail. These new larvae leave the body of the mollusk and re-enter the environment.
If the described transformations occur during high water, when the river floods the floodplain meadows, the larvae have a chance to catch on to the stalks of grass. After the water disappears, the flooded area turns into a beautiful pasture. Cows, sheep, horses eat grass together with larvae, providing new habitats for parasites.
A person should know how the larvae of these worms get on food. As a rule, this happens when watering onions, dill, lettuce and other crops with water from an infected reservoir.
Cestodes - the scourge of beef farming
Lovers of self-made low-fry steaks run the risk of contracting cestodes, or tapeworms. The long, flat body of these worms, reminiscent of crumpled white ribbons, can reach 8-10 m in length. But their fertility is especially impressive: during its 15-18 years of life, the parasite is able to lay up to 10 billion eggs.
The eggs are located in the terminal segments of the worm. Ripening, these segments break off and are carried out with feces. Thus, these worms enter the environment, being in a protective shell. Those who will survive on the pasture grass and will be eaten by a cow will survive. In the body of the animal, a larva will emerge from the egg and make its way into the oxygen-rich muscles, where it will turn into a Finn. Finna looks like a peppercorn, but white.
The danger is meat bought from hands. The seller may withhold information, and the buyer may not notice the Finns. They are not afraid of weak heat treatment, therefore any meat that has not passed veterinary control poses a threat to health.
An interesting way is that eggs, or rather the larvae of a sheep's brain, enter the environment. In order to guarantee the infection of the final owner - the wolf - the parasite changes the behavior of the sheep. By settling in her brain, he makes the animal not run when a predator appears, but spin in place.
Knowing how the eggs of worms get on the hands and food, we ourselves must strictly follow the rules of hygiene and teach this to children. It must be remembered that the treatment for worms is often long and is accompanied by side effects.