Parasitic disease

Key takeaways

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

Reference excerpt

A parasitic disease, also known as parasitosis, is an infectious disease caused by parasites. Parasites are organisms which derive sustenance from its host while causing it harm. The study of parasites and parasitic diseases is known as parasitology. Medical parasitology is concerned with three major groups of parasites: parasitic protozoa, helminths, and parasitic arthropods. Parasitic diseases are thus considered those diseases that are caused by pathogens belonging taxonomically to either the animal kingdom, or the protozoan kingdom.

Terminology Although organisms such as bacteria function as parasites, the usage of the term "parasitic disease" is usually more restricted. The three main types of organisms causing these conditions are protozoa (causing protozoan infection), helminths (helminthiasis), and ectoparasites. Protozoa and helminths are usually endoparasites (usually living inside the body of the host), while ectoparasites usually live on the surface of the host. Protozoa are single-celled, microscopic organisms that belong to the kingdom Protista. Helminths on the other hand are macroscopic, multicellular organisms that belong to the kingdom Animalia. Protozoans obtain their required nutrients through pinocytosis and phagocytosis. Helminths of class Cestoidea and Trematoda absorb nutrients, whereas nematodes obtain needed nourishment through ingestion. Occasionally the definition of "parasitic disease" is restricted to diseases due to endoparasites. Some parasitic diseases can occur in either an acute or chronic form. The acute form is characterized by quicker and often more severe onset of symptoms. The chronic form is typically less severe but is life-long. Some parasites that cause chronic and acute manifestations in their respective diseases are:

Trypanosoma brucei rhodesiense (acute) / Trypanosoma brucei gambiense (chronic) Trypanosoma cruzi Clonorchis sinensis Paragonimus westermani

Transmission

Infection Mammals can get parasites from contaminated food or water, bug bites, sexual contact, or contact with animals. Some ways in which people may acquire parasitic infections are walking barefoot, inadequate disposal of feces, lack of hygiene, close contact with someone carrying specific parasites, and eating undercooked foods, unwashed fruits and vegetables or foods from contaminated regions. Only at specific stages in a parasites life is it infectious. Contact with non-infective stages will not lead to infection. Many parasites utilize vectors to infect hosts. Vectors are vessels for the parasite, and help the parasite infect its next host. Some examples of parasitic diseases that use vectors are malaria, Lyme disease, and leishmaniasis.

At-risk groups Many parasitic diseases are concentrated in specific areas of the globe. Majority of these diseases are prevalent along the equator due to the warm temperatures. Therefore, people located in these areas are at greater risk of contracting the disease causing parasites. Parasitic diseases are far more common among marginalized groups. Lack of indoor bathrooms and access to clean drinking water are only some of the risk factors faced. Additionally, in the United States being Hispanic or African-American have shown to be risk factors for specific parasitic diseases.

Morbidity

Symptoms Parasitic diseases can manifest in many different symptoms, with some being asymptomatic. Many of the symptoms of parasitic diseases are common among other ailments, such as food poisoning or the flu. This can cause correct diagnoses to take a while. The target organ(s) of the parasite typically dictates the symptoms experienced:

General Source:

Fever Ulcers/lesions Death Headache Malaise Anemia Muscle Pain

Gastrointestinal Tract Source:

Dysentery Constipation Abdominal pain Vomiting Nausea Bloating Anorexia

Lungs Source:

Cough Blood in sputum Lesions

Skin Source:

Local inflammation Local dermatitis Hives Itching Rash

Treatment

Diagnosis Different parasitic diseases require different diagnostic methods because different parasites have different diagnostic stages. Testing routes will often be determined by symptoms.

Testing Source:

Stool Test Blood Test Colonoscopy/Endoscopy X-ray/MRI/ CT Scan

Therapies Parasitic infections can usually be treated with antiparasitic drugs. The use of viruses to treat infections caused by protozoa has been proposed.

See also Protozoan infection Babesiosis Giardiasis

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Parasitic disease

Start with the simplest possible case. Write down what Parasitic disease 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 Parasitic disease 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 Parasitic disease 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 Parasitic disease

In research: Parasitic disease 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 Parasitic disease 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: Parasitic disease is common in secondary-school and first-year university syllabi. It links to neighbouring topics Parasitic diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Parasitic disease 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 Parasitic disease in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Parasitic disease 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 Parasitic disease out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Parasitic disease in simple terms?

A parasitic disease, also known as parasitosis, is an infectious disease caused by parasites. Parasites are organisms which derive sustenance from its host while causing it harm.

Why does Parasitic disease 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 Parasitic disease?

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 Parasitic disease.