Animal Associations/ Relationships

Animal Associations/Relationships

In parasitology, various forms of associations exist between organisms, particularly between parasites and their hosts. These relationships can be harmful, neutral, or beneficial, depending on the nature of interaction.

Parasitism

• Definition: A relationship where one organism (the parasite) lives on or inside another organism (the host) and derives benefits, often causing harm to the host.
• Example: Plasmodium spp. (Malaria parasite) infects humans, causing disease while benefiting from nutrients.

Types of Parasitism:

1. Endoparasitism – Parasite lives inside the host. (e.g., Ascaris lumbricoides, Taenia solium)
2. Ectoparasitism – Parasite lives on the external surface of the host. (e.g., Ticks, Fleas, Lice)
3. Obligate Parasitism – Parasite cannot survive without the host. (e.g., Schistosoma spp.)
4. Facultative Parasitism – Can live freely but becomes parasitic when given the opportunity. (e.g., Naegleria fowleri)
5. Temporary Parasitism – Visits the host only for feeding. (e.g., Mosquitoes)
6. Permanent Parasitism – Remains in/on the host for life. (e.g., Tapeworms)

Commensalism

• Definition: One organism benefits while the other is neither harmed nor benefited.
• Example: Entamoeba coli, a non-pathogenic protozoan in the human intestine, benefits by feeding on intestinal contents without harming the host.

Mutualism

• Definition: Both organisms benefit from the relationship.
• Example: Termites and gut protozoa – Protozoa digest cellulose for termites, while termites provide a habitat and nutrients.

Phoresis

• Definition: One organism (the phoront) is transported by another (host) without harming it.
• Example: Bacteria carried by flies or mites attached to beetles for transport.

Predation vs. Parasitism

• Predation: One organism kills another for food (e.g., lion hunting a zebra).
• Parasitism: The parasite depends on the host but does not immediately kill it (e.g., tapeworms in intestines).

Hyperparasitism

• Definition: A parasite infecting another parasite.
• Example: A tapeworm inside a flea, which in turn parasitizes a dog.

Zoonosis & Host-Parasite Relationships

• Zoonosis: A disease that transmits from animals to humans (e.g., Toxoplasmosis, Rabies).
• Host Types:
  1. Definitive Host – Where the parasite reaches maturity and reproduces. (e.g., Humans for Taenia solium)
  2. Intermediate Host – Where larval or asexual stages occur. (e.g., Snails for Schistosoma spp.)
  3. Paratenic Host – A transport host, where no development occurs.
  4. Reservoir Host – Harbors parasites that can infect humans. (e.g., Rodents for Leishmania)