Difference Between Parasite and Parasitoid

Parasites and parasitoids are two different types of organisms that rely on other organisms for survival. Both are common in nature and have a significant impact on their hosts. However, there is a crucial difference between the two that sets them apart. In this essay, we will explore the differences between parasites and parasitoids in detail.

What are Parasites?

The term "parasite" comes from the Greek words para, which means "alongside," and sitos, which means "meal"; "parasitos" means "eating at another person's table." A parasite is another organism which receives nourishment from another organism, termed the host.

Parasites may or may not cause harm to their hosts, but they never gain anything from the parasitic connection. Certain endoparasites that reside inside the host are among the 70% of parasites that cannot be seen with the naked eye. Endoparasites need a third creature, termed a vector or carrier to be able to be transmitted to a host. On the other hand, those that live outside the body are termed ectoparasites.

Protozoa, helminths, and ectoparasites are the three primary categories of parasites that may infect people and cause illness (Centers for Disease Control and Prevention, 2016).

  • Protozoa are minute and unicellular organisms which can proliferate in people; those that dwell in the intestines are often found in contaminated food or water. For instance, the parasite Entamoeba histolytica is responsible for the symptoms of amebiasis, which include diarrhoea and stomach discomfort. Vectors spread protozoa that may replicate in human cells or circulate in the blood. The protozoan parasites of the genus Trypanosoma, which are transmitted to humans by the bites of tsetse flies, are one example of the cause of sleeping sickness.

  • Helminths are large, multicellular organisms that, in their adult form, cannot reproduce in humans. These include flatworms (e.g. flukes and tapeworms), thorny-headed worms or spiny-headed worms (thought to seldom infect humans), and roundworms (e.g. Ascaris lumbricoides which cause ascariasis, an infection of the small intestines) (e.g. Ascaris lumbricoides which cause ascariasis, an infection of the small intestines).

  • Ectoparasites are creatures that burrow into the skin; for example, ticks, lice, and fleas infest the skin and its appendages. They spread pathogens.

What are Parasitoids?

Parasitoid organisms are those that spend their whole lives inside or on a host and ultimately kill that host.

  • Properties − Eggs may be laid either within or outside of the host body by parasitoids. After hatching, the larvae feeds on the host organism. Most parasitoids belong to the Hymenoptera order of insects; it is not uncommon, for example, to find many wasp pupal cases on the carcass of a caterpillar host. It's not uncommon for a parasitoid to solely live off just one host.

  • Types of organisms that are parasitoids − Insects that are endopterygotes, meaning that their life cycle includes a pupal stage, are hosts to parasitoids. As a rule, it is the larval stage that parasitizes the host.

  • Morphological adaptations of parasitoids − Several parasitoids have specialised egg-laying mechanisms that allow them to attach to or enter the host arthropod. The ovipositor of a wasp, for example, can break through the cuticle of its insect victim. When the legs have hatched inside the host, the larvae will grow and develop inside until they are ready to pupate, at which time they will emerge from the host and complete the life cycle outside. As a result, the insect host perishes.

  • Examples of parasitoids − Parasitoids can only be found in the Hymoptera, Diptera, and Coleoptera orders. The Hymnoptera order, which includes wasps, has the highest prevalence of parasitoids among the three orders of insects.

Differences: Parasite and Parasitoid

The following table highlights the major differences between Parasite and Parasitoid −





Parasites are described as organisms that feed off of and live within a host, but do not necessarily kill it.

A parasitoid is any kind of life form that not only parasitizes but also invariably destroys its host.

Kills host

The death of a host may be contributed to by a parasite, but this is unusual.

The death of a parasitoid's host is always the result of the parasitoid's direct actions.

Live inside the body of the host

Endoparasites are parasites that develop within of their hosts.

A subset of parasitoids, called endoparasitoids, actually does make its home inside the host.

Live outside the body of the host

When parasites reside on the exterior of their hosts, they are referred to as ectoparasites.

Ectoparasitoids are parasitoids that do not dwell inside the host animal.

Host organisms

Parasites may be found on just about anything, from insects to worms to flies to birds to mammals to plants.

Parasitoid organisms can only infect arthropods.


Roundworms, tapeworms, flukes, hookworms, fleas, and ticks are all parasites that live on animals; dodder is a parasite that lives on plants; and Plasmodium is a protist parasite that lives on animals.

The majority of arthropod parasitoids are insects belonging to the order Hymenoptera, with some exceptions in the orders Diptera and Coleoptera.


Parasites and parasitoids are two distinct types of organisms that rely on other organisms for survival. While both can have a significant impact on their hosts, the difference lies in the outcome of their relationship with the host.

Parasites do not kill their hosts, while parasitoids ultimately do. Understanding these differences is important for understanding the role these organisms play in ecosystems and the impact they can have on other species.

Updated on: 18-Apr-2023


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