Intro to Parasitology and Parasites of medical importance Flashcards
What are medically important parasites?
(a) Protozoa
(b) Worms (helminths):
- Nematodes (roundworms)
- Cestodes (tapeworms)
- Trematodes (flukes)
What is a Parasite?
Organisms, animals or plants that live on or in a host and draws nutrients directly from it, benefiting at the expense of the host
- The parasite offers nothing to the relationship, creating an arrangement which may be neutral or harmful, but never positive
- Some parasitic relationships are harmless, while in other cases a parasite can damage or kill its HOST
- Para (beside) Sitos (food)
- Ectoparasites / Endoparasites
Which parasites are unicellular and which are multicellular?
Unicellular→ Protozoa
Multicellular→ Helminths
What are the 2 main groups of medically important parasites and their common locations?
- PROTOZOA (systemic / gastrointestinal)
- HELMINTHS (worms) (systemic / gastrointestinal)
Gastrointestinal Parasites have two main stages?
Active stage
Infective stage
What are the properties of the active and infective stage of protozoa?
• Protozoa
(A)Active eg. TROPHOZOITE: causes disease / symptoms
(B)Infective eg. PROTOZAN CYST: dormant, resting stage; excreted in faeces; contaminates vegetation and water
What are the properties of the active and infective stage of helminths?
(A)Active eg. ADULT WORM, LARVAE: causes disease / symptoms
(B)Infective eg. WORM EGGS: contains larvae; excreted in faeces;
contaminates vegetation and water
LARVAL STAGE: dormant in the tissue and organs of birds, mammals and fish
What are the main features of a worm?
mouth-cutting plates
intestine
ovary
larva (3mm)
What is a Parasite Host?
•Organism eg. human that harbours a parasite (eg protozoa, worm) providing nourishment and shelter
What are the two types of host?Save
(a) DEFINITIVE HOST: supports the sexually mature, reproducing adult parasite
(b) INTERMEDIATE HOST: supports the immature or non-reproductive forms of a parasite (larval stage)
How does protozoa’s utilisation of a host differ from that of worms?
•Some parasites (eg protozoa) utilise a definitive host only whilst others (eg worms) may utilise one (or more) intermediate hosts before maturing in its definitive host
Transmission of Gastrointestinal Parasites to Humans: Environomental contamination
Protozoan cysts+ Worm eggs→Environmental Contamination→
Consumption of contaminated water, fruits/ vegetation
+ Fruits / veg washed with contaminated water
+ Shellfish feeding on contaminated water
Transmission of Gastrointestinal Parasites to Humans: Intermediate Host Infection
Worm larval stage (present in the ‘meat’ of the intermediate host→ Intermediate Host Infection→ Consumption of contaminated undercooked beef /pork /fish and squid
ie Consumption of the intermediate host
Classify parasites of medical importace based on cellularity, reproduction and hosts