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Parasitic infections and what you should know about them

Summertime can put us on a higher risk for parasitic infections. Parasites are organisms that live and feed off other organisms, known as hosts, in order to survive. They rely on their host for shelter, nutrients, and reproduction. Sources of infection include:

  • contaminated water

  • contaminated soil

  • contaminated food

  • vectors.


There are various types of parasites that can infect humans and other animals. Here are some common types of parasites:

1. Protozoa. Protozoa are single-celled parasites. They can be classified into different groups based on their characteristics and modes of transmission. Some examples include:

  • Plasmodium. This genus of protozoa causes malaria, a mosquito-borne disease.

  • Entamoeba histolytica. It is responsible for amoebic dysentery, a gastrointestinal infection.

  • Giardia lamblia. This parasite causes giardiasis, a diarrheal illness transmitted through contaminated water.

2. Helminths (Worms). Helminths are multicellular parasites that can be categorized into two main groups:

  • Roundworms (Nematodes). Examples include hookworms (Ancylostoma duodenale, Necator americanus), whipworms (Trichuris trichiura), and threadworms (Strongyloides stercoralis). Roundworms typically enter the body through contaminated soil or fecal-oral transmission.

  • Flatworms (Platyhelminths). Examples include tapeworms (Taenia saginata, Taenia solium), liver flukes (Fasciola hepatica, Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis felineus), and blood flukes (Schistosoma spp.). These parasites often infect humans through ingestion of contaminated food or water.

3. Ectoparasites. Ectoparasites are external parasites that live on the surface of their host's body. They include:

  • Ticks. Ticks can transmit diseases such as Lyme disease, babesiosis, and tick-borne encephalitis.

  • Fleas. Fleas are known for causing discomfort and transmitting diseases like bubonic plague and typhus.

  • Lice. Lice infestations, including head lice, body lice, and pubic lice, can cause itching and skin irritation.

  • Mites. Mites can cause conditions such as scabies (Sarcoptes scabiei) and mange in animals.

  • Flies. Certain fly species can act as vectors for parasitic infections e.g., Tsetse flies (transmits African trypanosomiasis known as sleeping sickness).

  • Sandflies. They can transmit leishmaniasis, a disease caused by the Leishmania parasite.

  • Mosquitoes. Mosquitoes are well-known vectors for several parasitic diseases such as: malaria, Dengue fever, Zika virus,West Nile virus.

These are just a few examples of the many types of parasites that exist. Each parasite has its own lifecycle, mode of transmission, and associated diseases. It's important to understand and take appropriate precautions to prevent parasitic infections, especially in regions where they are prevalent or during specific activities that may increase the risk of exposure. To minimize the risk of parasitic infections, it's important to:

  • wash hands before meals and thoroughly cooking food

  • cook eggs, meats and fish

  • wash well fruits and vegetables

  • drink safe and clean water

  • avoid swimming in potentially contaminated source

  • practice safe sex

  • check yourself, your family members and pets for ticks after spending time outdoors

  • regular deworm of pets

  • use natural insect repellents and protective clothing to prevent mosquito and tick bites.


Parasitic infections can vary in severity, ranging from mild discomfort to serious and potentially life-threatening conditions. Some common symptoms of parasitic infections include:

  • digestive issues; constipation or diarrhea, flatulence, irritable bowel syndrome (IBS)

  • fatigue, exhaustion

  • weight loss

  • skin problems: rashes, itching, rosacea

  • respiratory problems: shortness of breath, cough

  • joint or muscle pain

  • difficulty falling asleep or waking up throughout the night

  • mood changes

  • iron and/or vit. B12 deficiency

  • grinding of teeth at night

  • constant hunger.

Parasitic infection may remain unnoticed or give a rise to clinical disease due to several mechanism:

  • production of specific enzymes leading to tissue necrosis e.g., E. histolitica causes ulcers

  • direct mechanical damage to the tissue e.g., hookworm damages intestinal villi

  • allergic response e.g., Ascaris can lead to eosinophilic pneumonia

  • physical obstruction e.g., roundworm masses cause intestinal obstruction

  • inflammation e.g., Schistosoma haematobium may lead to bladder fibrosis

  • malignancy e.g., Clonorchis sinensis may lead to bile duct carcinoma and S. haematobium may cause urinary bladder cancer.


The diagnosis of a parasitic infection typically involves a combination of medical history, physical examination, and laboratory tests (stool test, blood test, imaging studies). Specific diagnostic methods and tests will vary depending on the suspected parasitic infection. However, it's important to note that only small percent of parasitic infections are found by laboratory tests. Some parasites can migrate form the intestine to the tissues and no longer be found in the feaces. In many cases diagnosis should be made based on clinical presentation. In practice, it is often worth doing a treatment trial when the symptoms point to parasites and when laboratory tests point to persistent, unexplained anemia or vitamin B12 deficiency.

If you suspect you have a parasitic infection or have been exposed to parasites, it is recommended to consult with a health professional for diagnosis, treatment, and management of the condition.



Paniker, C.K.J and Ghosh, S (2017). Paniker's Textbook of Medical Parasitology. Jaypee Brothers Medical Publishers Pvt. Limited.

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