Helminthiasis

Key takeaways

Helminthiasis belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Helminthiasis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Helminthiasis from memory before moving on to harder problems.

Reference excerpt

Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms, known as helminths. There are numerous species of these parasites, which are broadly classified into tapeworms, flukes, and roundworms. They often live in the gastrointestinal tract of their hosts, but they may also burrow into other organs, where they induce physiological damage. Soil-transmitted helminthiasis and schistosomiasis are the most important helminthiases, and are among the neglected tropical diseases. These group of helminthiases have been targeted under the joint action of the world's leading pharmaceutical companies and non-governmental organizations through a project launched in 2012 called the London Declaration on Neglected Tropical Diseases, which aimed to control or eradicate certain neglected tropical diseases by 2020. Helminthiasis has been found to result in poor birth outcome, poor cognitive development, poor school and work performance, poor socioeconomic development, and poverty. Chronic illness, malnutrition, and anemia are further examples of secondary effects. Soil-transmitted helminthiases are responsible for parasitic infections in as much as a quarter of the human population worldwide. One well-known example of soil-transmitted helminthiases is ascariasis.

Types of parasitic helminths

Of all the known helminth species, the most important helminths with respect to understanding their transmission pathways, their control, inactivation and enumeration in samples of human excreta from dried feces, faecal sludge, wastewater, and sewage sludge are:

soil-transmitted helminths, including Ascaris lumbricoides (the most common worldwide), Trichuris trichiura, Necator americanus, Strongyloides stercoralis and Ancylostoma duodenale Hymenolepis nana Taenia saginata Enterobius Fasciola hepatica Schistosoma mansoni Toxocara canis Toxocara cati Helminthiases are classified as follows (the disease names end with "-sis" and the causative worms are in brackets):

Roundworm infection (nematodiasis) Filariasis (filarial worms: Wuchereria bancrofti, Brugia malayi infection) Onchocerciasis (Onchocerca volvulus infection) Soil-transmitted helminthiasis – this includes ascariasis (Ascaris lumbricoides infection), trichuriasis (Trichuris infection), and hookworm infection (includes necatoriasis and Ancylostoma duodenale infection) Trichostrongyliasis (Trichostrongylus spp. infection) Dracunculiasis (guinea worm infection) Baylisascaris (raccoon roundworm, may be transmitted to pets, livestock, and humans)

Tapeworm infection (cestodiasis) Echinococcosis (Echinococcus infection) Hymenolepiasis (Hymenolepis infection) Taeniasis/cysticercosis (Taenia infection) Coenurosis (T. multiceps, T. serialis, T. glomerata, and T. brauni infection)

Trematode infection (trematodiasis) Amphistomiasis (amphistomes infection) Clonorchiasis (Clonorchis sinensis infection) Fascioliasis (Fasciola infection) Fasciolopsiasis (Fasciolopsis buski infection) Opisthorchiasis (Opisthorchis infection) Paragonimiasis (Paragonimus infection) Schistosomiasis/bilharziasis (Schistosoma infection)

Acanthocephala infection Moniliformis infection

Signs and symptoms

The signs and symptoms of helminthiasis depend on a number of factors including: the site of the infestation within the body; the type of worm involved; the number of worms and their volume; the type of damage the infesting worms cause; and, the immunological response of the body. Where the burden of parasites in the body is light, there may be no symptoms. Certain worms may cause particular constellations of symptoms. For instance, taeniasis can lead to seizures due to neurocysticercosis.

Mass and volume In extreme cases of intestinal infestation, the mass and volume of the worms may cause the outer layers of the intestinal wall, such as the muscular layer, to tear. This may lead to peritonitis, volvulus, and gangrene of the intestine.

Immunological response As pathogens in the body, helminths induce an immune response. Immune-mediated inflammatory changes occur in the skin, lung, liver, intestine, central nervous system, and eyes. Signs of the body's immune response may include eosinophilia, edema, and arthritis. An example of the immune response is the hypersensitivity reaction that may lead to anaphylaxis. Another example is the migration of Ascaris larvae through the bronchi of the lungs causing asthma.

Secondary effects

Immune changes

In humans, T helper cells and eosinophils respond to helminth infestation. It is well established that T helper 2 cells are the central players of protective immunity to helminths, while the roles for B cells and antibodies are context-dependent. Inflammation leads to encapsulation of egg deposits throughout the body. Helminths excrete into the intestine toxic substances after they feed. These substances then enter the circulatory and lymphatic systems of the host body. Chronic immune responses to helminthiasis may lead to increased susceptibility to other infections such as tuberculosis, HIV, and malaria. There is conflicting information about whether deworming reduces HIV progression and viral load and increases CD4 counts in antiretroviral naive and experienced individuals, although the most recent Cochrane review found some evidence that this approach might have favorable effects. Helminth infection also lowers the immune responses to vaccination for other diseases such as BCG, measles, and Hepatitis B.

Chronic illness Chronic helminthiasis may cause severe morbidity. Helminthiasis has been found to result in poor birth outcome, poor cognitive development, poor school and work performance, decreased productivity, poor socioeconomic development, and poverty.

… excerpt ends here. Continue reading the full article.

Illustrations

Helminthiasis: Ascaris life cycle: Adult worms in the lumen of the small intestine (1). The female produces eggs (approximately 200,000 per day) that are excreted with the feces (2). Unfertilized eggs are harmless, but fertilized ones are infective after 18 days to several weeks (3). Infective eggs are ingested (4), enter the gut (5), develop into larvae in the intestine, and penetrate the blood vessel to enter lungs, where they develop further (6), after 10 to 14 days, penetrate the alveolar walls, ascend the bronchial tree to the throat, and are re-swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). It takes 2 to 3 months for one complete cycle. Adult worms can live 1 to 2 years. — Ascaris life cycle: Adult worms in the lumen of the small intestine (1). The female produces eggs (approximately 200,000 per day) that are excreted with the feces (2). Unfertilized eggs are harmless, but fertilized ones are infective after 18 days to several weeks (3). Infective eggs are ingested (4), enter the gut (5), develop into larvae in the intestine, and penetrate the blood vessel to enter lungs, where they develop further (6), after 10 to 14 days, penetrate the alveolar walls, ascend the bronchial tree to the throat, and are re-swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). It takes 2 to 3 months for one complete cycle. Adult worms can live 1 to 2 years.

Worked examples

Example 1 — a first encounter with Helminthiasis

Start with the simplest possible case. Write down what Helminthiasis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Helminthiasis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Helminthiasis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Helminthiasis

In research: Helminthiasis appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Helminthiasis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Helminthiasis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Abdominal pain, Ascaridomorpha, Conditions diagnosed by stool test, so understanding it makes those chapters shorter.
In everyday life: Look for Helminthiasis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Helminthiasis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Helminthiasis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Helminthiasis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Helminthiasis in simple terms?

Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms, known as helminths. There are numerous species of these parasites, which are broadly classified into tapeworms, flukes, and roundworms.

Why does Helminthiasis matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Helminthiasis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Helminthiasis.