Difference Between Parasite and Pathogen


Main Difference

The main difference between parasite and pathogen is that a parasite is a type of pathogen while a pathogen is a disease-causing agent.

Parasite vs. Pathogen

A parasite feeds, grows and shelters in or on the host organism without contributing to the survival of the host whereas pathogen is an organism that produces a disease in the host. Parasites can be multicellular like worms and unicellular for example protozoa whereas pathogens are mostly unicellular for example bacteria, virus, etc. Parasites cause diseases in hosts, but in some cases, they can be beneficial for the host, for example, some protozoa species have a specific function for digestion of cellulose in the grass within the rumen of a cow. But pathogens are always disease-causing agents for their hosts. Protozoa, helminths, and ectoparasites are main types of parasites whereas pathogens types include virus, bacteria, fungi, protozoa, helminths, and rickettsia.


Comparison Chart

A parasite is that organism which lives on the body of the host at host’s expenseA pathogen is an organism which causes disease in the host
Level of Organization
Prokaryotic OrganismsEukaryotic Organisms
Macroscopic organismsEither microscopic or macroscopic organisms
A few causes diseases in the host’s bodyAll causes diseases In the host’s body
Malaria, Amoebic dysentery, Giardiasis, Trichomoniasis, Cryptosporidiosis, ToxoplasmosisCommon cold, Influenza, AIDs, Tetanus, Food poisoning, Whooping cough, German measles, Bubonic plague, Cellulitis, Trichinellosis, Lyme disease
Symptoms of diseases
Allergies, Anemia, Abdominal pain, Change in the bowel, Skin problems, Joint pain(hives), Weight loss, Fatigue, Constipation, Diarrhea, Nausea, Vomiting, Bloating, DizzinessMalaise, High fever, Headache, Redness, Rash, Swelling, Fluid drainage, Hot incision site, Muscle soreness
Fecal tests, Endoscopy, Colonoscopy, X rays, Magnetic resonance imaging (MRI), Computerized axial tomographyImmunologic tests, Culture tests, Microscopy, Nucleic acid-based identification, and non-nucleic acid-based identification method
Protozoans and helminthsBacteria, fungi, virus, prions, protists, and parasites

What is Parasite?

A parasite always depends on its host for survival because it lives in the host and depends on it for nutrition and usually it harms the host. It cannot live, grow and reproduce without a host. For this reason, a parasite doesn’t kill its host, but it spreads diseases and proves fatal. Usually, the Parasites are smaller than their hosts and multiply very fast. It uses the host’s resources to fuel its life cycle. Parasites vary widely. Almost 70% parasites are not visible to the naked eye, for example, malarial parasite but some type of worm parasites can reach over 30 meters in length. The parasite is not a disease itself, but it spreads diseases and has different effects. There are three types of parasites; Protozoa, Helminths, and Ectoparasites.

  • Protozoa: These are single-celled organism known as Plasmodium. Protozoa can only reproduce within the host.
  • Helminths: These are worm parasites. Schistosomiasis is caused by a helminth. Other examples of this category are roundworm, pinworm, trichina spiralis, tapeworm, and fluke.
  • Ectoparasites: These types of parasite live on the host and include lice and fleas.


  • Ensuring food is fully cooked.
  • You are using insect or mosquito repellant.
  • Knowing the kind of parasite prevalence in the area, you may travel.
  • Drink water from bottles while traveling.
  • Take care while bathing in rivers or lakes

What is Pathogen?

The pathogen is anything which causes disease in the host. Humans are called as exposed when they are in contact with pathogens and considered infected when pathogens enter the body and cause infections. There are six types of pathogens; viruses, bacteria, fungi, protozoa, helminths, and Rickettsia.

  • Virus: Virus is tiny infectious agents that multiply only inside the cells of the host body. It contains DNA and RNA genome in a protein shell which is called capsid. The virus has the potential to infect all types of life, animals, plants and even microorganisms.
  • Bacteria: Bacteria comprise single cells that can thrive in diverse environments. They are a few micrometers in length and have different shapes like rod, spiral, and spheres. Bacteria cause mostly fever, chills, inflammation of the lungs, cough, and shortness of breath.
  • Fungi: These include yeast, mushroom, and mold. These are single-celled or multi-celled parasite organism.
  • Protozoa: These are a tiny single-celled microorganism that causes disease-causing toxins. Malaria is a disease produced by protozoans.
  • Helminths: These are parasitic worms which are visible to naked eye. These feed on a live host to get energy, nutrients, and protection and produce sickness and fatigue in the host.
  • Rickettsia: These are pathogens which grow inside the living cells and are similar to bacteria for example Typhus.


  • Wash your hands frequently.
  • Get vaccinated
  • Use antibiotics on doctor’s recommendation only.
  • Stay at home if you have symptoms.
  • Practice safer sex
  • Don’t share personal items.
  • Travel wisely

Key Differences

  1. A parasite is an organism which lives in or at another organism at the expense of the host’s body whereas pathogen is a disease-causing agent.
  2. There are mainly three types of parasites whereas pathogens are of six kinds.
  3. Most of the parasites are prokaryotic organisms except fungi whereas all pathogens are eukaryotic organisms.
  4. All parasites are macroscopic organisms whereas pathogens can be either microscopic or macroscopic organisms.
  5. All parasites are not disease-causing agents whereas all pathogens cause diseases in hosts.
  6. Parasites cause diseases like amoebic dysentery and malaria whereas pathogens cause diseases like food poisoning, influenza, aids, etc.
  7. Some plants are also parasites, but pathogens are always microorganisms.


Parasite and pathogen are two types of agents that can cause diseases in the host. Parasites depend on the host organism for its benefits. Most parasites are microscopic organisms. Pathogens are purely disease-causing agents which can be microscopic or macroscopic organisms. The main difference between both is the relationship between the two types of organisms and their pathology.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White