Parasitology Basics

Parasitology Basics

# Relationships Between Organisms

There are four main types of relationships between organisms:

• Mutualism: Two organisms live together, both benefiting.

• Commensalism: Two organisms live together, one benefits, the other is neither harmed nor helped.

• Saprotrophism: An organism lives on dead organic matter. There are two types:

• Endosaprophytes: Organisms living inside dead organic matter.

• Exosaprophytes: Organisms living on the surface of dead organic matter.

• Parasitism: An organism lives on or in another organism (host) to obtain food and shelter, causing harm to the host.

# Types of Parasites

There are six types of parasites:

• Obligate parasites: Must live as parasites to survive.

• Facultative parasites: Can live as parasites or freely.

• Endoparasites: Live inside the host’s body.

• Ectoparasites: Live on the surface of the host’s body.

• Erratic parasites: Move to a different organ than where they typically parasitize.

• Aberrant parasites: Live on a different animal than their usual host.

# Specificity of Parasites

• Host specificity:

• Narrow: Only one specific host.

• Broad: Many different hosts.

• Site specificity:

• Narrow: One specific organ.

• Broad: Multiple different organs.

# Host

• Definitive host: Contains the adult or mature stage of the parasite.

• Intermediate host: Contains the larval or immature stage of the parasite and is not the primary host.

• Primary host: Often parasitized.

• Secondary host: Occasionally parasitized.

• Reservoir host: Animal carrying the parasite that infects humans.

# Transmission Vectors

• Transmission vector: Insects or mollusks carrying the parasite and transmitting it from one person to another.

• Biological transmission vector: The parasite can develop and multiply within the vector.

• Mechanical transmission vector: The parasite does not multiply within the vector.

# Asymptomatic Carrier

A person carrying the parasite without showing symptoms.

# Life Cycle

The way a parasite exists in the environment or within the host. Stages continuously follow one another.

# Human as a Dead-End Host

• True dead-end host: Development is arrested, the parasite is destroyed.

• Circumstantial dead-end host: Does not develop but persists for a long time until eaten by a predator.

# Life Cycle of Intestinal Parasites

• Direct short: The parasite infects immediately upon leaving the host.

• Direct long: The parasite requires time to develop in the environment.

• Indirect: Requires one or two intermediate hosts.

# Transmission Routes

• Digestive tract

• Skin

• Respiratory system

• Sexual intercourse

• Placenta

• Blood transfusion

# Diagnosis

• Three rights:

• Right place

• Right type

• Right time

# Prevention

Interrupting one link in the parasite’s life cycle.