Clinical Parasitology: Human Parasites Classification

Study Notes

Protozoa: Classified by motility into four classes:
- Sarcodina: Movements via pseudopodia, sluggish.
- Mastigophora: Motile by flagella.
- Ciliophora: Movement through cilia.
- Sporozoa: Non-motile.
Nematoda: Two main subcategories based on chemoreceptors:
- Phasmidea/Aercentea/Phamids: Contains caudal chemoreceptors located at the posterior end.
- Aphasmidea/Adenephorea/Aphasmids: Possesses cervical chemoreceptors at the anterior.
Platyhelminthes: Segmentation differentiates types:
- Cestoda: Multiple segments; categorized into two orders based on uterine pore presence.
  - Pseudophyllidea: No uterine pore.
  - Cyclophyllidea: Uterine pore present.
- Trematoda: One segment or unsegmented.
Arthropoda: Function as vectors, with classes including:
- Insecta: Characterized by wings.
- Arachnida: Defined by legs.
- Mollusca: Identified by shells.
Pentastomids: Known as tongue worms.
Acanthocephala: Referred to as thorny-headed worms.

Types of Parasites:
- Obligatory: Cannot survive outside of a host.
- Facultative: Can exist independently and become parasitic if needed.
- Endoparasite: Lives inside the host.
- Ectoparasite: Lives on the exterior of the host.
- Erratic: Found in an unusual organ for the species.
- Permanent: Lives on/in the host for its entire life span.
- Temporary: Interacts with the host for a brief period.
- Spurious: Free-living, passes through the digestive tract without causing infection.
Types of Hosts:
- Accidental: Hosts that are not the usual for the parasite.
- Definitive: Where the adult sexual phase of the parasite occurs.
- Intermediate: Hosts where the larval asexual phase takes place.
- Reservoir: Hosts harboring parasites that can infect humans.
- Transport: Transfers parasites from one host/location to another.
- Carrier: Hosts that harbor parasites without showing symptoms.
- Vector: Arthropods that transmit parasites; can be biological or mechanical.

Exposure: Inoculation of an infective agent.
Infection: Establishment of an infective agent within the host.
Incubation Period: Time from infection to symptom development.
Pre-patent Period: Duration until evidence of infection is observable.
Autoinfection: Infected individual serves as their own infection source. Notable examples include:
- Enterobius vermicularis: Hand-to-mouth transmission.
- Capillaria philippinensis: Internal reproduction.
- Hymenolepis nana: Transmission noted.
- Strongyloides stercoralis: Self-inoculation potential.
Superinfection: Hyperinfection occurring in an already infected individual by the same species, leading to a more severe parasitic load.