Lecture Notes: Chapter 12 - Parasites

Overview

• Focus on parasites, often referred to as 'Things That Go Bump in the Night'.
• Brief overview due to complexity of parasitology.
• Recognize organisms as helminths (worms), protists, or fungi.
• Supplemental videos provided for better visual understanding.
• Definitions and examples using ticks as a familiar reference.

Definitions and Examples

Parasite

• An organism that lives at the expense of a host, benefiting while the host suffers damage.

Ectoparasite

• Lives on the surface of the host.
• Example: Ticks and lice.

Endoparasite

• Lives inside the host.
• Example: Tapeworms, requiring strong drugs for removal.

Temporary Parasite

• Feeds on host temporarily and then leaves.
• Example: Ticks and mosquitoes.

Obligate Parasite

• Requires a host for at least part of its life cycle.
• Example: Malaria (a protist).

Facultative Parasite

• Can live independently but prefers a host for nutrients.
• Example: Certain fungi.

Accidental Parasite

• Unintentional hosts like humans and pets.

Hyperparasitism

• Parasites carrying other parasites.
• Example: Ticks carrying diseases like Lyme disease.

Transmission and Vectors

Biological Vector

• Transports parasites during part of its life cycle.
• Example: Mosquitoes carrying malaria.

Mechanical Vector

• Transports parasites without involvement in life cycle.
• Example: Flies transferring parasitic eggs accidentally.

Host Types

Definitive Host

• Host where parasite reproduces.
• Example: Humans for malaria.

Intermediate Host

• Temporary host during life cycle.
• Example: Snails for certain parasites.

Reservoir Host

• Infected organism providing parasites to others.
• Example: Pets like dogs and cats.

Evasion of Host Immune Response

• Formation of cysts to avoid immune detection.
• Antigenic variation: Changing surface markers to evade immune system.
• Decoy antigens to mislead immune response.
• Some can hide in immune cells or within host cells.

Life Cycles and Reproduction

Schizogony

• Parasite makes multiple copies of itself.

Hermaphroditic Reproduction

• Contains both male and female parts for self-reproduction.

• Example: Tapeworms.

• Focus on malaria life cycle as a primary example.

Conclusion

• Parasites exhibit complex life cycles and evasion strategies.
• Understanding requires extensive study beyond this overview.