Micro 20 - Lab exam 2: Parasitic Protozoa and Helminths

What is the infective stage of protozoa?

Cysts

- resisting dormant stage that helps the organism surive the environment

What is the vegetative stage of protozoa?

Trophozoite

- actively feeding, metabolizing and reproducing stage

Entamoeba histolytica

pseudopodian parasite of class Sarcodina that causes amebic dysentery

infective, resistant cysts are released from the lumen of the itnestine through fececs and are deposited in water, soil, or on vegetation

upon digestion the mature quadrinucleated cyst wall disintegrates and the nuclei divide producing eight active trophozoites that move to the colon where they establish infection

Entamoeba histolytica cyst

Infection by ingestion of cysts in contaminated drinking water

- causes diarrhea, dysentery and liver abscess

- has chromatid bar

Dx: fexal exam/serological test

Entamoeba histolytica cyst pic2

Balantidum coli

- ciliated parasitic protozoan similar to E.histolytic, but does not multiply within the cyst

- organism resides primarily in the lumen and submucosa of colon

- causes ulceration and alternating constipation and diarrhea

Balantidum coli cyst

Has double walled yeast cell

Balantidum coli trophozoite

Has cytostome (mouth) and micronucleus is outside of macronucleus

ciliated

Giardia lamblia cyst

Ingestion of cysts in contaminated drinking water

- Oval with well defined cyst wall

- four nuclei present at one pole

Giardia lamblia trophozoite

Has a kite shape, and flagella

Helminths

multicellular eukaryotic animals that generally possess digestive, circulatory, nervous, excretory, and reproductive systems

- some are free living in soil or water, and some are parasites of humans, animals, or plants

- cause infectious diseasesl disagnosed by microscopic examination of eggs or larvae

- eggs may have striations, a spine, or operculum (hatch where eggs leave)

Life cycle of parasitic helminths

- highly modified compared to free-living helminths

- lack sense organs and sometimes digestive systems

-reproductive system is complex w/ characteristics that promote infeciton of new hosts

Dioecious helminths

separate male and female

Monoecious (hermaphroditic)

male and female reproductive systems in one animal

Intermediate host

an organism that supports the immature or nonreproductive forms of a parasite

- some parasites have a different host for each larval stage

Ex. humans may be intermedaite host for dog tapeworm

Definitive host

Adult (reproductively mature) stage of parasitic helminth lives in the definitive host

-humans can serve as definitive host for beef, pork, and fish tapeworms

Paragonimus westermani

Lung fluke

- oval ova, have an operculum (lid)

- golden in color

-shell has unevne thickness

-snails and crayfish are intermediate host

man is definitive host

Schistosoma mansoni

- Penetration of skin by larva

-dx by fecal exam for eggs

- blood fluke / flatworm

Taenia solium

Ingestion of Larvae or eggs, (if eggs, man is intermediate host, if larvae, pig is int. host.)

- pork tapeworm

- dx: fecal exam for tapeworm eggs or exam of affected tissues for larvae

Enterobius vermicularis (roundworm)

- pinworm

- very abundant like grains of rice

- egg shape with one flat side

- larvae worm folded in half

-transparent shell

Eggs = infective form

dx: fecal exam for eggs / scotchtape method

Ascaris lumbricoides (roundworm)

Eggs = infective form

dx: fecal exam for eggs

Trichuris trichuria (roundworm)

has two pinched ends

eggs = infective form

dx: fecal exam for eggs

"whipworm"

Necator americanus (hookworm&roundworm)

Larvae = infective form

dx: fecal exam for eggs

Trichenella spiralis (encysted larvae / roundworm)

Infective form: larvae

Man eats pork/bear meat containing larvae which then mature in man's intestine & reproduce; second generation larvae hatch and migrate through the body to become encysted in muscle tissue

Flatworms

Trematodes/flukes: flat, leaf shaped bodies with ventral and oral suckers

- obtain food by absorbing it through their "cuticle" outer covering

Cestodes/tapeworms - intestinal parasites

- has a scolex (head) which contains suckers for attaching to the intestinal mucosa of definitive host and some may have hooks

- Proglottids = body segments

Roundworms

Nematodes - cylindrical and taper at each end

- have complete digestive system (mouth, intestine, anus)

- Most are dioecious

- males have spicules to guide sperm

Ova

Eggs

Larvae

morphologically distinct juvenile forms