Education, Infectious Diseases

A Guide to Parasitic Infections and Parasites

Author Kimberly Hazel , 10-May-2022

A parasite is an organism that lives on or inside another organism (the host) and feeds off of it. The relationship between a parasite and its host can be beneficial, harmful, or neutral. In some cases, the parasite may not cause any noticeable harm to the host. Some parasites are specialized to live on a particular type of host, while others are generalists and can live on a wide variety of hosts.


In other cases, parasites can cause disease in their hosts. Most parasites live in the digestive system or on the skin of their hosts, where they can get easy access to food or warmth. Some parasites live inside their hosts’ bodies and may even invade the host’s tissues. Many parasites are much smaller than their hosts. 


Some parasites are transmitted from one individual to another, while others are acquired through contact with contaminated food or water. Some are easy to detect and treat, while others can be difficult to detect and very difficult to treat. Despite our best efforts, parasites will always be a part of human life.


What is a Parasitic Infection and How Does it Impact Health?


A parasitic infection is a condition caused by parasites. Parasites can cause a variety of infections, ranging from mild to deadly and some cause adaptive immune responses. These infections can be transmitted in a number of ways. Symptoms of a parasitic infection vary depending on the parasite involved. They can range from mild to severe and may include fever, diarrhea, nausea, and weight loss. Treatment for a major parasitic disease typically involves taking antimicrobial medications. In severe cases, hospitalization may be necessary.


The Most Common Infections


According to the Centers for Disease Control and Prevention (CDC), there are three parasite infections that are most common in the United States: giardiasis, cryptosporidiosis, and cyclosporiasis.

Giardiasis, often called “beaver fever,” is caused by the parasite Giardia lamblia and is typically spread through contaminated water, food, or contact with an infected person. Symptoms include diarrhea, cramping, nausea, and vomiting.

Cryptosporidiosis, also known as “crypto,” is caused by the parasite Cryptosporidium parvum and can also be spread through contaminated water or contact with an infected individual. It is particularly dangerous for young children and people with weakened immune systems. Symptoms of cryptosporidiosis include watery diarrhea, abdominal cramps, nausea, and vomiting.

Cyclosporiasis is caused by the parasite Cyclospora cayetanensis and is typically spread through contaminated food or water. Symptoms of this infection include diarrhea, fatigue, weight loss, nausea, vomiting, and abdominal cramps. If you think you may have a parasite, it is important to see a doctor so that you can receive treatment.


Parasite Types


The three main types of parasites that cause disease in humans are protozoa, helminths, and arthropods.

Protozoa are single-celled organisms that can multiply in the human body. Many protozoa are acquired by ingestion of contaminated food or water or by contact with contaminated soil. Malaria, giardiasis, and trichomoniasis are examples of diseases caused by protozoa.

Helminths are worm-like parasites that can grow to be very large. They generally live in the intestine but some helminths can travel through the blood to other organs where they can cause disease. Helminths are usually acquired by ingestion of contaminated food or water or by contact with contaminated soil. Intestinal worms such as hookworms, roundworms, and tapeworms are examples of helminths that can cause disease in humans.

Arthropods are parasitic insects that can transmit diseases to humans through their bites. These include mosquitoes, fleas, lice, and ticks.




There are many different types of parasitic diseases, and the symptoms can vary depending on the type of parasite involved. Some common symptoms include abdominal pain, diarrhea, fatigue, and weight loss.

However, it is also possible to have an infection without any noticeable symptoms. In some cases, the only way to know for sure that you have a parasite is to have a laboratory test performed. If you think you may have a parasite, it is important to see a doctor.


How Are They Diagnosed?


Parasitic infections can be difficult to diagnose because they often cause nonspecific symptoms that can be attributed to a variety of other illnesses. In addition, many parasites are not easily detected by standard laboratory tests. As a result, diagnosis often relies on a combination of clinical suspicion and specialized testing.

Blood tests, stool samples, and radiographs may be used to identify parasites or their eggs in the body. Ultrasound or CT scans may also be helpful in some cases. Most are diagnosed by identifying the parasites in the patient’s tissue or body fluids. This can be done using a light microscope, although more sophisticated techniques such as DNA testing may also be used. In some cases, diagnosis may be based on the symptoms the patient is experiencing.

For example, malaria is typically diagnosed based on the presence of characteristic feverish bouts. In other cases, diagnosis may be made by exclusion, which means that other conditions with similar symptoms are ruled out until a parasitic infection is the only remaining possibility. In general, these infections are easier to diagnose if the parasites are found in large numbers in the patient’s body. However, even a small number of parasites can cause serious harm and should be treated accordingly.




In most cases, parasitic infections are treatable with medication. The type of medication used will depend on the specific parasite involved. These infections are typically treated with antiparasitic medications. The specific medication or combination of medications used will depend on the type of parasite involved and the severity of the infection. In most cases, parasitic infections can be successfully treated with antiparasitic drugs. However, some infections, such as those caused by the Guinea worm, do not have an effective treatment currently available. In other cases, surgery may be necessary to remove the parasite from the body.


What is an Antiparasitic and How Does it Work?


Antiparasitic drugs work by interfering with the parasite’s ability to survive and reproduce. For example, some antiparasitic drugs work by preventing the parasite from feeding on its host’s blood. Other antiparasitic drugs work by causing the parasite to expel its eggs. In addition, some antiparasitic drugs can be used to treat infections caused by protozoa, which are single-celled parasites. In some cases, antiparasitics may also be used to prevent infections from occurring in the first place.

Antiparasitic drugs are available in both oral and topical formulations. There are a variety of different antiparasitic medications available, and the specific medication that is used will depend on the type of parasite that is causing the infection. Common antiparasitic drugs include albendazole, mebendazole, and ivermectin. In some cases, more than one drug may be necessary to achieve effective eradication of the parasite. For example, treatments for tapeworm infections often require a combination of drugs. When used correctly, antiparasitics can be highly effective in treating these infections.


Modes of Transmission: How Parasites are Spread


There are a few different ways that parasites can spread. These are known as modes of transmission. These modes include contact, airborne, droplet, vectors, and vehicular (contaminated inanimate objects such as food, water, and fomites).

Contact Spread or Surface Spread


Many people are familiar with the idea of contact spread, whereby a pathogen is transmitted from one individual to another through physical contact. However, surface spread is also a common mode of transmission for many parasites. This occurs when a parasite comes into contact with an intermediate surface, such as a doorknob or countertop, and is then transferred to the next individual who touches that surface.

Ultimately, parasites can spread through both contact and surface spread, depending on the specific parasite and the circumstances involved. These parasites can then enter the body through the skin or mucous membranes.

The most common example of a surface-spread parasite is Giardia, which is often found in contaminated water. Some parasites, such as lice, can also be transmitted through contact with contaminated clothing or bedding. In general, any parasite that can be spread through close contact or contaminated surfaces has the potential to be transmitted through surface spread or contact spread.


Airborne Spread


In some cases, parasites may also be able to spread through the air, although this is less common.


Droplet Spread


There is currently no scientific evidence to suggest that parasites can be spread through droplet spread (such as coughing or sneezing). However, it is possible that parasites could be spread through contact with infected bodily fluids, such as blood or feces.

If an infected person were to cough or sneeze on someone else, there is a possibility that the parasite could be transmitted through exposure to bodily fluids. While there is no definitive evidence that parasites can be spread through droplet spread, it is important to take precautions to avoid exposure to bodily fluids if you are in close contact with someone who is infected.


Vector Spread


It is certainly possible for parasites to spread through vector spread. Vectors are typically larger animals, such as rats or mosquitoes, that can carry parasites from one place to another. Once a vector comes into contact with a potential host, the parasite may enter the host’s body through a bite or sting. Once inside the host, the parasite may reproduce and spread to other parts of the body. In some cases, the parasite may also be passed on to other animals through the vector.


Vehicular Spread: Food or Water Contamination


While parasites can spread in a number of ways, the vehicular spread is not typically a major concern. This is because most parasites require a direct host-to-host transmission in order to complete their life cycle. In other words, they need to come into contact with their host’s blood or tissue in order to survive. However, there are a few exceptions.




When it comes to preventing parasitic infections, there are a few key things to keep in mind. First, it is important to practice good hygiene and cleanliness. This means washing your hands regularly, especially after using the restroom or coming into contact with contaminated surfaces. You should also avoid sharing personal items, such as towels, toothbrushes, or razors, with others. Second, it is important to be aware of the signs and symptoms of parasitic infections so that you can seek medical treatment early if necessary. Finally, it is a good idea to take preventive measures when traveling to areas where parasitic infections are common. This may include wearing protective clothing and using mosquito nets when sleeping. By following these simple tips, you can help to prevent yourself from becoming infected with a parasitic infection.

Kimberly Hazel

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