Parasite

-an organism that lives on or in the body of another organism (the host) and causes damage to the other organism

Types of Parasites

Ectoparasites - live/feed on the exterior of an organism (tick)
Endoparasites - live/feed on the interior of an organism (tapeworm)

We will focus on two kingdoms:
Protist parasites and Animal Parasites

Parasitic Protists

Disease: Malaria (Phylum Sporozoa)
Protist: Plasmodium
Vector: Anopheles Mosquito
Symptoms: Chills, fever
See Life Cycle of Malaria

Disease: Cryptosporidosis (Phylum Sporozoa)
Protist: Cryptosproridium
Vector: Contaminated water
Symptoms: diarrhea, nausea, vomitting

Disease: African Sleeping Sickness (Phylum Zoomastigophora)
Protist: Trypanosoma
Vector: Tse Tse Fly
Symptoms: uncontrolled sleepiness
See Life Cycle of Trypanosoma

Disease: Hiker's Diarrhea (Phylum Zoomastigophora)
Protist: Giardia lamblia
Vector: contaminated water
Symptoms: diarrhea, vomitting, cramps

Disease: Amebic Dysentery (Phylum Rhizopoda)
Protist: Entamoeba Histolytica
Vector: Contaminated water
Symptoms: diarrhea

Most parasites are contracted from water sources, either directly ingesting contaminated water, or being infected through the skin. The best way to prevent parasitic infections is to have a clean water supply and waste treatment.


Animal Parasites

Roundworms - Phylum Nematoda

Ascaris - common roundworm, found in dogs, cats and humans; infection occurs from ingestion

Hookworm - attaches to intestine, causes bleeding, infection occurs through the skin
Hookworm Infection

Pinworms - commonly infect children in all parts of the world (including US), causing itching around the anus but does not usually cause any other health problems

Guinnea Worm
--also known as fiery worm, or dracunculus
-- worms found just under skin, cause burning
--see Life Cycle of Guinnea Worm | Video: Guinea Worm

Trichinella--worm embeds in muscles
--humans become infected from eating undercooked pork
--symptoms include soreness and tenderness of the muscles

Filariasis

Filarial worms are tissue-dwelling parasites. The parasite is transmitted by mosquitoes. After infection, the adult filarial worms migrate to and live in the lymphatic ducts of humans. There, they clog up the blood vessels and cause the enlargement of the various body parts (elephantiasis). The worms then infiltrate connective tissue.
--Image 1 -- Image 2

Flatworms

Phylum Platyhelminthes

Schistosoma
--blood fluke
--intermediate host is a water snail
--humans are infected through the skin by larval form (cercariae)
-- Schistosomiasis results in approx. 1,000,000 deaths per yer
--See Life Cycle of Schistosoma

Taenia
--tapeworm found in cattle and pigs
--can infect humans
--segments called proglottids for reproduction
--head is the scolex (see slide)

Liver Fluke
--this flatworm has several species that inhabit a variety of animals
--Fasciola hepatica - common sheep liver fluke
--Fasciolopsis buski - infects humans (See Life Cycle)

 

Web Resources on Parasites

http://www.dpd.cdc.gov/DPDx/