ParasitologyParasitologyParasitologyParasitology

What are parasites and What are parasites and what do they cause?what do they cause?

Parasitology Protozoan

Single cell organism belonging to Kingdom Protista.

Of 20,000 species only a few cause disease

Helminth Platyhelminth (Flatworm) Aschelminth (Roundworm) Multicellular, most free-living A few are parasites

Protozoan: Motility Sarcodina (amoeba) - move by extending

projections, pseudopods, from cytoplasm Mastigophora (flagella) - whip-like

movement that pull cell through medium Ciliaphora (cilia) - propel cell through

medium, similar but shorter than bacteria flagella

Apicomplexia (sporozoa) – no observed independent movement

Biology of Protozoans Aerobic heterotrophs, areas with water Reproduction, asexual or sexual Encystment – under adverse conditions,

produce protective capsule cyst Survive without food, water, oxygen;

unsuitable temperature or chemical conditions

For parasites allows survival outside host

Medically Important Protozoan

Intestinal Amebae Entamoeba

Intestinal & Urogenital Flagellates Giardia, Trichomonas

Ciliates Balantidium

Sporozoa Plasmodium

Amebae: Entamoeba histolytica Amebic dysentery (diarrhea with blood

and mucous) Bores through intestinal wall to cause

ulcers in intestine and liver Two stages – trophozoite (motile) and cyst Transmitted from human to human via

cyst passed in feces and ingested by next host

Diagnosis – trophozoite or cyst in feces

Ciliates: Balantidium coli Dysentery - severe, rare type of

dysentery Two stage life cycle – trophozoite and

cyst Humans acquire by ingestion of cysts

passed in feces Diagnosis - cyst or trophozoite in feces

Flagellates: Giardia lamblia

Traveler’s diarrhea, hiker’s diarrhea Acute or chronic enteritis, common in

children Found in small intestine By ingestion of cyst passed in feces Diagnosis by finding trophozoite or cyst

in feces

Flagellates: Trichomonas vaginalis

Vaginitis Only trophozoite stage, must be

quickly transferred from host to host Inhabits female vaginal tract and

male urinary tract Transmitted as STD, contaminated

toilet facilities or towels

Sporozoa: Plasmodium Malaria, complex life cycle Mature forms are obligate intracellular

parasites Anopheles mosquito bite and inject

sporozoite (infective stage for humans) Exoerythrocytic cycle: Sporozoite goes

to liver, undergo schizogony, produces merozoites

Erythrocytic cycle: Merozoites released, either reinfect new liver cells or infect RBC

Erythrocytic Life Cycle In RBC, transforms into

trophozoite (a ring consisting of nucleus and cytoplasm)

Ring stage enlarges and divides repeatedly to form many merozoites

RBCs rupture and merozoites released

Causes fever and chills (a febrile paroxysm)

Most merozoites reinfect new RBCs and undergo a new cycle of asexual reproduction

Sexual Cycle In Mosquito Some merozoites develop into

male and female sexual forms (gametocytes)

Gametocytes picked up by mosquito when feeding on infected host, enter intestine to begin sexual cycle

Male and female gametocytes unite into zygote, forms cyst intestine wall

Cell division occurs, asexual sporozoites formed

Cyst ruptures, sporozoites migrate to salivary glands of mosquito from where injected into new human host

Helminths Reproductive systems of parasitic

species highly developed Life cycle – may be extremely

complex and many different host Definitive host – harbors adult,

sexually mature helminth Intermediate host – harbors larval

or developmental stage

Platyhelminth: Flatworm Dorsoventrally flattened and either

lack or incomplete digestive system Trematodes (flukes)

Intestinal – Fasciola Blood – Schistosoma

Cestodes (tapeworms) Intestinal -Taenia

Blood Fluke: Schistosoma Schistosomiasis Adults live in mesenteric and pelvic veins of

humans Cercaria are not ingested but burrow

through skin of human host and enter circulatory system

Fresh water snails as intermediate host Diagnosis by finding eggs in urine and feces

Intestinal Tapeworms Head (scolex) has suckers, hooks; attach intestinal

mucosa Lack digestive system, absorb food through cuticle Body of segments (proglottids) continually produced Proglottid contains both male and female organs Gravid proglottid furthest from scolex filled with eggs

Tapeworms: Taenia Humans as definitive host –

Taenia saginata (beef tapeworm) Tania solium (pork tapeworm).

Adult Taenia found in humans Mature proglottids with eggs are

released in feces (diagnosis) Upon ingestion by cattle or pigs,

larvae hatch and encyst in muscles as cysticercus

Then ingested by humans eating undercooked beef or pork

Aschelminths – Roundworms

Complete digestive system Most dioecious (male reporductive organs in

one and female in another) Class Nematode has human parasites No complicated life cycles Eggs infective for humans:

Enterobius Ascaris

Larvae infective for humans: Necator

Pinworm: Enterobius vermicularis Spends entire life in

humans Adult worms in large

intestine Female migrates to anus

to deposit eggs, causes itching, most common symptom

Eggs ingested by host or another human (commonly transmitted in young children by poor hygiene)

Diagnosis – pick up using sticky tape method and observe by microscopy

Roundworms: Ascaris lumbricoides

Large – 30cm. in length Adults live in small intestine of humans,

pigs, horses Eggs excreted in feces, survive in soil Infection occurs by ingesting eggs Diagnosis by finding eggs in feces

Hookworm: Necator americanus Adults live in small

intestine, eggs excreted with feces

Hatch in soil, larva enter new host by penetrating skin

Go to blood and lungs, swallowed and get to small intestine to mature into adult

Diagnosis by finding eggs in feces

To prevent infection – wear shoes

MICR 301Final Exam (200 pts.)

Tuesday, Dec. 6, 2011 8:00 – 10:30am Lecture, Reading, Key Terms, Learning

Assessment Questions, Five Case Study Virus, Bacteria, Fungi, Parasite Lectures Part I (~65%): Mechanism of

Pathogenesis thru Parasites Part II (~35%): Introduction thru

Specific Host Defense Objective (M.C., Terms, T/F), Short Essay

QUESTIONS???

ALL I REALLY NEED ALL I REALLY NEED TO KNOWTO KNOW

ALL I REALLY NEED ALL I REALLY NEED TO KNOWTO KNOW

ALL I REALLY NEED TO KNOW I LEARNED IN

KINDERGARTEN

• Robert Fulghum

ALL I REALLY NEED TO KNOW

• about how to live and what to do and how to be I learned in kindergarten.

• Wisdom was not at the top of the graduate-school mountain, but there in the sandpile at Sunday School.

These are the things I learned:

• Share everything.• Play fair.• Don’t hit people.• Put things back where you found

them.• Clean up your own mess.

• Don’t take things that aren’t yours.

• Say you’re sorry when you hurt somebody.

• Wash your hands before you eat.• Flush.

• Warm cookies and cold milk are good for you.

• Live a balanced life – learn some and think some and draw and paint and sing and dance and play and work every day some.

• Take a nap every afternoon.

• When you go out into the world, watch out for traffic, hold hands, and stick together.

• Be aware of wonder.• Remember the little seed

in the Styrofoam cup:• The roots go down and

the plant goes up and nobody really knows how or why, but we are all like that.

• Goldfish and hamsters and white mice and even the little seed in the Styrofoam cup – they all die.

• So do we.

• And then remember the Dick-and-Jane books and the first word you learned – the biggest word of all –

• LOOK.

LOOK• Fulghum, Robert.• 1988. All I Really Need To Know I

Learned In Kindergarten: Uncommon Thoughts On Common Things. New York: Villard Books.

• 2003. 15th Anniversary Edition. All I Really Need To Know I Learned In Kindergarten: Reconsidered, Revised & Expanded, With Twenty-Five New Essays. New York: Ballantine Books.

ALOHA

Kauai, Hawaii