Protists + Helminths

Euglena

• use a organelle called a flagellum to swim

• They have chloroplasts to perform photosynthesis.

Paramecium

• have cilia that cover their entire surface to help them swim/move

Amoeba (or Ameba)

• move using temporary extensions of their cytoplasm called pseudopodia (singular: pseudopodium), often referred to as "false feet".

Leishmania

• cause Leishmaniasis

• The parasite has a single flagellum in its promastigote stage, which allows it to move

• Humans get infected through the bite of an infected sandfly

• The sandfly transmits the parasite while feeding on blood.

Vector of Leishmania

• Sandfly (size of a fruit fly)

Trypanosoma (in blood smear)

• Have flagella

• Know how human can be infected

• Western Hemisphere, bloodsucking bugs (“kissing bugs”) carry trypanosomes

• The bugs defecate while feeding, and infection results when a person rubs infected feces into the bite wound or eye

Trichomonas

• Cause Trichomoniasis

• Have flagella

• Primarily through sexual contact (person-to-person during intercourse)

• It is a sexually transmitted infection (STI)

Giardia (cysts)

• cysts are shed in the host’s feces

• they don’t cause symptoms but are the infective form

Giardia (trophozoite)

• Have flagella

• Die quickly outside host

• Not infective

• In host’s small intestine, cause the GI symptoms

Entameba (cyst)

• Causes Amoebiasis

• Cysts are shed in host’s feces

• When a trophozoite, Entameba moves using pseudopods

• Cysts are the infective stage, trophozoites cause symptoms

Humans get infected with Entameba by ingesting its cyst form, usually in fecally-contaminated food or water

• Can ulcerate the intestinal lining, cause abscesses

Balantidum (trophozoite)

• Causes Balantidiasis or Balantidiosis

• Common in the host’s small intestine

• Trophozoites cause the symptoms of balantiasis

• Trophozoites have cilia

• They don’t live long outside the host, not infective

Plasmodium (ring stage)

• on a blood smear

• Causes malaria

• Female mosquitoes, as they feed on blood, transmit this from person to person

Fasciola hepatica egg

• Commonly found in water

• Expelled in the feces of the infective definitive host

Life cycle of Faciola hepatica

Fasciola hepatica miracidium larva fluke

• What hatches out of the eggs

• Found swimming in water until die ( 8 hours) or encounter appropriate host snail

• Stained red, blue-green, or purple

• Bullet shape, same width as microscope pointer on 10x

• has cilia

Fasciola hepatica redia larva

• Found in the body of appropriate host snail (IH)

• Developing cercariae (red objects) inside the redia

Fasciola hepatica cercaria larva

• Found swimming in water, after leaving the snail

• Does not last very long

• swim

Fasciola hepatica metacercaria larva

• During this stage these worms are found on aquatic plants

• Will remain in this stage until they die or a suitable DH eats the plants

Fasciola hepatica adult (stained)

• Hemaphroditic

• Found in the liver and bile ducts of DH

• Lay numerous eggs and are shed in the host’s feces

Fasciola hepatica adult (unstained)

• Hemaphroditic

• Found in the liver and bile ducts of DH

• Lay numerous eggs and are shed in the host’s feces

Schistosoma adults (male and female)

• Found coupled like this when in the intestinal blood vessel, liver tissue, intestinal wall of DH

• Male is the shorter thicker part

• Female is the longer leaner part

• 240 million people worldwide are infected with various species of schistosomes

Adult Tapeworm Anatomy

Taenia Eggs (Tapeworm)

• Shed in the feces of the DH

• Sometimes encased in proglottids

Taenia pisiformis cysticercus

• Tapeworm cysticercus larva

• Larval stage found in muscle and/or viscera of worm IH

• Hooks are hard to see, but are visible in the photo

Taenia pisiformis

• Thousands of tiny brown eggs are visible inside the low power views of a mature proglottid

Taenia pisiformis mature (upper) and gravid (lower)

(proglottids)

• The presence of fertilized eggs are in the gravid proglottids

• Mature proglottids contain the sex organs

• Gravid proglottids are shed in DH feces

Echinococcus life cycle

Echinococcus granulosus adult

• Has scolex’s sucking discs

• The hooks are visible on the very top of the scolex

• Canids are the usual definitive hosts; deer and other grazing animals are the usual intermediate hosts

• Humans occasionally ingest Echinococcus eggs, becoming accidental intermediate hosts

• life-threatening disease (hydatid disease, or cysticercosis) may result due to tissue damage by the developing larvae

Cysticercosis

• MRI shows numerous tapeworm larvae (dark, hole-like objects) in a human brain

Enterobius (pinworm)

• Adults live in the human colon, emerging at night onto the perianal skin to mate and lay eggs

• Humans become infected by ingesting these eggs, and that symptoms are mostly confined to perianal itching and discomfort

Necator (hookworm)

• historically common in American South

• Adults live attached by their mouthparts to the human intestinal wall

• A heavy hookworm infestation can cause anemia

Enterobius v. Necator

(it’s about the mouthparts!)

• Enterobius’s mouth is small and pipette-lie

• Necator’s mouth has sharp, toothlike “cutting plates”.

Trichinella spiralis (4 or 5 encysted worms visible here)

• This is a slice of tongue (or other skeletal muscle) from an infected pig

• larval stage

• Trichinosis is very rare in the U.S. today, but humans can become infected by consuming undercooked pork or sometimes bear meat