Parasitology Flashcards
What is a Parasite?
Organisms that Occupies Host + Draws Nutrients Directly From Them
- Parasite Offers Nothing to Relationship
- Benefits at expense of Host
- Arrangement is Neutral/Harmful, never +tive
What Are The 2 Main Parasite Groups?
Protozoa:
Single-cell Eukaryotic Micro-organisms
Found in Water, Soil
Helminths:
Multicellular Parasitic Worms
Obligate parasites
What Are The Parasitic Stages?
Protozoa
Active: Trophozoite causes disease
Infective: Cyst, a resistant transmissible form, survives for extended time periods
Helminths
Active: (Worms, Larvae) Cause Disease
Infective: (Eggs) a resistant transmissible form, survives for extended time periods
What Is A Parasite Host?
An Organism that Provides Nourishment and Shelter
What Are The 2 Types Of Hosts?
Definitive Host:
Supports sexually mature, reproducing adult parasite
Intermediate Host:
Supports immature/non-reproductive forms of parasite
Some parasites use definitive host only
Other parasites utilize 1/more Intermediate Host Before Maturing In Definitive Host
What Are The General Characteristics of Protozoa?
- Unicellular
- Eukaryotic (Membrane Bound
Organelles) - Asexual Reproduction: produces
Daughter Cells with DNA Identical To
Parents Protozoan - Forms Cysts (Dormant Form,
Consumed By Host) - Classified According to Locomotive
Apparatus
(Movement with Specialize Structures)
How Do Protozoa obtain Nutrition?
Via:
- Pinocytosis
- Engulfing
- Cytosome
List Some Protozoa.
- Amoeba
- Apicomplexans
- Ciliates
- Flagellants
Give An Example of a Medically important Amoeba.
Entamoeba Histolytica
- Causes Amoebiasis
- invades intestinal lining, can spread to
liver - Causes Ulcers, Tissue Destruction,
Bloody Diarrhea, Abdominal Pain - Mimics Other Diseases (Symptom
Overlap)
What is Balantidium Coli?
- Largest protozoan Parasite Of
Humans - Only Ciliate Pathogenic To Humans
- Commonly found In Pigs/Cattle
What Is Giardia Intestinalis?
Waterborne Protozoan parasite Causing Giardiasis, Diarrheal Disease
Colonizes Small Intestines of Humans + Animals
2 Forms:
Trophozoite:
Pear Shaped, motile feeding stage with 8 flagella + ventral suction disk
Cyst:
Infectious, dormant stage with protective wall, shed in feces
What Is Toxoplasma Gondii?
Obligate Intracellular Protozoan Parasite
Causes Toxoplasmosis
3 Infectious Stages:
Tachyzoites:
Rapidly Dividing, invasive form during acute infection
Bradyzoites:
Slow-Growing, Dormant Form In Tissue Cysts
Oocysts: Environmentally resistant
Spores
Definitive Host: Cats
Intermediate Hosts: Humans, Birds, Rodents, Livestock
What Are the 3 Main Categories Of Helminths?
Nematodes (Roundworms)
Cestodes (Tapeworms)
Trematodes (flukes)
What Are The General Characteristics of Nematodes?
Eukaryotic/Multicellular Cylindrical Parasites with a Complete Digestive Tract
They are Dioecious (Male + Female)
They Are Transmissional via Ingestion of Eggs or Larval Penetration Through Skin
Undergo 4 Moults + 4 Larval Stages To Reach Adult Stage
Give An example Of a Medically Important NEMATODE.
Enterobius Vermicularis (PINWORM):
Nematodes (Roundworm) that use Eggs (Infective Stage) on Human (Definitive Hosts)
Mechanism:
- Eggs Ingested Via Contaminated Hands/Food
- Eggs Hatch In Small Intestine ➜ Larvae
Released - Larvae Move ➜ Large Intestine ➜ Mature
Into Adult Worms - Pinworms Mate In Large intestine
- Female Worms Travel + Lay Eggs in Anal
Region - Egg Hatching ➜ Causes Itching/Irritation
- Itching ➜ Eggs Transferred under
Fingernails, Onto Hands
What Are The general Characteristics Of Cestodes (Tapeworms)?
- Scolex (Head with Suckers/Hooks to Attach
To Intestinal Wall) - Tegument: No Digestive System (Nutrient
Absorption Directly Through Tegument) - Hermaphroditic (Male + Female
Reproductive Organs) - Require Intermediate Host (Which
Consumes Eggs) - Segmented
- Have Organs
Describe Taenia saginata (Beef Tapeworm)
- Eggs Excreted ➜ Passed In Environment
- Embryonated Eggs Ingested By Cattle
- Eggs Hatch ➜ Penetrate intestinal Wall
- Circulate to Musculature in Cattle
- Infection From Undercooked/Infected Beef
What Are The General Characteristics Of Trematodes (Flukes)?
- Flat, Oval/Leaf Shaped
- Hermaphroditic
- Tegument (Protection, Nutrient Absorption +
Immune Evasion) - Primitive DS: Actively Digests Host
Tissues/Blood
Life Cycle Involves:
Multiple Intermediate hosts
Various Sexual + Asexual Development Stages
Give An Example Of A Trematode.
Fasciola hepatica (Fluke)
- Unembryonated eggs passed in feces →
Released into the environment - Eggs Embryonate In Water (Develop Into
Miracidia) - Miracidia Hatch In Water → Actively
Penetrate Snail Tissue (Intermediate Host) - In The Snail:
- Miracidia → Sporocysts → Rediae →
Cercariae (asexual reproduction)
- Miracidia → Sporocysts → Rediae →
- Cercariae Exit Snail → Encyst as
Metacercariae on aquatic vegetation - Definitive host (e.g., sheep, humans) eats
vegetation - Metacercariae excyst in intestine → Migrate
To Liver → Develop Into Adult flukes In Bile
Ducts
