ParasitologyParasitology What are parasites and 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 301 Final 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 TO 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 All I Really Need To Know I Learned In Kindergarten: Uncommon Thoughts On Common Things. New York: Villard Books th 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