Topic: Ascaris lumbricoides (human roundworm) and pinworms

Author: Elżbieta Szedzianis

Target group

6th‑grade student of the elementary school.

Core curriculum

4 ) Nematodes. Student:

a) explains the environment and life style of nematodes;

b) observes nematodes representatives (photos, films, diagrams, etc.) and explains the common features of this group of animals;

c) presents the routes of invasion of parasitic nematodes (trichina worm, roundworm and pinworm) and discusses methods of preventing human diseases caused by these parasites;

d) shows the importance of nematodes in nature and for human beings;

Lesson objectives

Students describe the routes of invasion of roundworm and pinworms, their vital functions and significance.

The criteria for success

• you will explain how roundworm and pinworm eggs spread;

• you will list two methods of protection against roundworm and pinworm infection.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• social and civic competences.

Methods/forms of work

Working with text, alternative observation, a game of bingo, puzzle.

Individual activity and activity in pairs.

Teaching aids

• abstract;

• interactive whiteboard or traditional blackboard;

• tablets/computers;

• dices;

• bingo gameboard;

• plasticine or polymer modelling clay.

Lesson plan overview

Introduction

1. The teacher informs the students that, during the classes, they will learn about nematodes and pinworms - the most common human parasites. The teacher asks students what organisms are called worms and roundworms. The teacher explains the meaning of both concepts, functioning both in colloquial language and in biological terminology.

2. The teacher specifies the subject and the objective of the lesson as well as the criteria for success.

Realization

1. Students read the first paragraph of the abstract, presenting the body structure of nematodes. Then, they make plasticine models of a human roundworm which has got a slender body.

2. The teacher asks students to draw up a table, listing the features of the body structure of a roundworm and a tapeworm as well as their adaptations to parasitism. Students agree on the consecutive positions of the first column (features that will be compared). The teacher helps them precisely the wording. Students fill the table. Volunteers share the results of their work. The students indicated by the teacher throw a dice. Students who have thrown the highest number of pips assess the way in which their colleagues complete the task. The teacher corrects any mistakes.

3. The teacher instructs the students to look at the illustration showing the development cycle of human roundworm. Students describe its course, showing on themselves the consecutive stages of human roundworm’s journey through the human body.

4. The students order the elements of the interactive puzzle depicting the roundworm's development cycle.

5. The teacher encourages the students to read a fragment of the abstract devoted to the pinworms. Students explain why it is often the case that soon after a child is infected with pinworms in kindergarten or school, every person living with the child gets infected.

6. Students do interactive exercise no. 1.

Summary

1. Students name items and places where pinworm or human roundworm eggs may be found. They formulate conclusions on how to avoid infection with worms.

2. The teacher invites students to play bingo. The teacher distributes the boards and explains the rules of the game (Appendix No. 1).

Appendix no. 1

Rules of the game

1. The first letters of the terms to be guessed are written on the board. Empty fields are considered filled.

2. The teacher explains subsequent terms. When students recognize the term, they write it on the board.

3. If someone completes the names of the three terms vertically or horizontally,he/she shouts „Bingo” and stops the game for a moment. This person must then read out the terms and provide their correct definitions. If he/she does it, he/she gets 1 point.

4. The game continues until someone completes all the names. He/she then shouts the word „Bingo” twice and provides explanations of these terms that have not yet been defined. He/she receives 15 points, but decreased by the number of points gained by players who also shouted “Bingo”.

Terms hidden on the board:

nematodes, parasites, host, human roundworm, proglottid, hygiene, larvae, intestine, infection, faeces, digestive system, pinworm, cysticercus, tapeworm, worm.

Homework

Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Nematodes

Nematodes are vermiform animals. They are elongated, they do not have a separate head. Their body is slender cylindrical (elongated and round in cross‑section), spindly at both ends. Similarly to flatworms, their body is bi‑laterally symmetrical, and the front and rear part may be distinguished. The free‑living forms found among them occur in soil, fresh and salt waters. The nematodes also include internal parasites of animals, such as: human roundworm, pinworm, trichinella spiralis or human whipworm, and of plants, e.g. beet cyst eelworm. Unlike flatworms, nematodes have an open gastrointestinal tract beginning with a mouth and ending with an anal hole. Nematodes do not have respiratory, circulatory or hard skeletal systems. Their body is filled with fluid that gives them shape and elasticity and allows the muscles to perform movements. The body colour of most nematodes is usually light cream or pink, just like flatworms.

Parasitic nematodes show numerous adaptations to such a mode of life. Unlike parasitic flatworms, they do not have specialised clasping organs. They attach themselves to the wall of the host's intestine with the help of lips, which surround their mouth. They do not have a separate head or neck. Parasitic nematodes, just like flatworms, can use aerobic and anaerobic respiration, and they intake respiratory gases and water with the entire surface of their body. Their body is covered with a thick layer of cuticle, just like in flatworms. Cuticle in free‑living forms protect against mechanical injuries, and in internal parasites it protects against the harmful effects of digestive fluids. Human roundworm, living in the host's intestine, feeds on nutrients contained in food digested by human. A distinct sexual dimorphism occurs. Female roundworms are even twice as large as males, they are up to 40 cm long. Whereas males, unlike females, have got a bent rear end of the body.

Parasitic nematodes usually stay in the host's body throughout their lives, in which they hatched from eggs. They can occur in large quantities. Most nematodes, unlike flatworms, are dioecious animals.

Adult roundworms live in the small intestine of a human. Females produce approximately 200,000 eggs daily. Larvae develop in eggs. Such larvae‑containing eggs escape to the external environment with faeces and may contaminate water, vegetables or fruit. After ingestion by a human, the egg casings are digested in the intestine, and the larvae released from them pierce the intestinal wall and enter the blood vessels. Together with the bloodstream, they migrate to various organs: the liver, the heart, and finally they reach the lungs, where they break through the alveoli walls and migrate to the bronchi and trachea. The irritated trachea reacts with an expectorant reflex, which causes the larvae to enter the throat. Swallowed with saliva, they return to the small intestine. There, they mature sexually and reproduce.

Pinworm just like a roundworm has only one host – a human. Most people infected with this nematode are kindergarten children and their families because pinworm infection is very contagious. Unlike roundworms, pinworms live in the large intestine, not in the small intestine. At night, adult females lay eggs in the anus. The egg‑covering secretion causes unpleasant itching. The child, scratching, introduces eggs under the nails, from where they reach objects in its surroundings. They can also be transmitted to the mouth, then the so‑called autoinfection occurs. Prevention of pinworm infection is primarily a strict adherence to personal hygiene rules.

Flatworms and nematodes are perceived by humans mainly as parasitic worms that seriously threaten not only health, but even life. They also cause dangerous animal diseases. They cause considerable losses in pigs and cattle breeding. They can infect pets, mainly dogs and cats, from which humans get infected. Therefore, we should remember about regular deworming of pets and adherence to basic hygiene rules, especially about washing hands after playing with them.

When buying wild game, we need to be sure that it has been tested and does not contain flatworm or nematode larvae. It is risky to eat raw meat, especially from home slaughter.

Parasitic nematodes living of plants can cause significant crop losses, up to 50% yields. It is worth noting, however, that worms have a positive impact on the environment, e.g. they regulate the number of zooplankton in the ecosystem, eliminate weaker individuals and provide food for snails and fish. Saprobionts in the soil take part in the processes of its formation.

• Nematodes are worms with elongated, filamentous, limbless body with round cross‑section.

• Most nematodes, such as human roundworms, pinworms, trichinella spiralis, are parasitic organisms. Only one host is present in their developmental cycle.

• Adaptations of internal parasites to their mode of life consist, among others, in a very high fertility, reduction of sensory organs, immunity to digestive fluids, the ability to respirate anaerobicly.