Transcript PowerPoint Presentation - I. Introduction to class

 Medically
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1. Amoeboflagellates (Phylum Sarcomastigophora)
Move using pseudopods (false feet) or flagella.
A. Amoebas (Subphylum Sarcodina)
Move by extending blunt, lobelike projections
(pseudopods).
Amoebas engulf food with pseudopods and phagocytize it.
Several species cause amoebic dysenteries of varying
degrees of severity.
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Important Protozoa
Entamoeba hystolytica: Feeds on red blood cells. Produces
dysentery and extraintestinal cysts.
Dientamoeba fragilis: Found in 4% of humans. Usually
commensal. Can cause chronic, mild diarrhea.
Other diseases include:
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Meningoencephalitis: Caused by Naegleria fowleri. Penetrate
nasal mucosa of swimmers in warm waters. Mortality rate
almost 100%.
Keratitis: Caused by Acanthamoeba. Can cause blindness.
Associated with use of contact lenses.
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B. Flagellates (Subphylum Mastigophora)
Move by one or more whiplike flagella. Some parasitic
flagellates have up to eight flagella.
Most are spindle shaped with flagella projecting from
anterior end.
Outer membrane is a tough pellicle. Food is ingested
through an oral groove or cytosotome.
Important pathogens:
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Trichomonas vaginalis: Causes genital and urinary infections.
Has undulating membrane. Lacks a cyst stage. Transmitted
sexually or by fomites.
Giardia lamblia: Causes a persistent intestinal infection
(giardiasis) with diarrhea, nausea, flatulence, and cramps. In
U.S. most common cause of waterborne diarrhea. About 7% of
U.S. population are healthy carriers.
Trypanosoma brucei gambiense: Hemoflagellate (blood parasite).
Causes African sleeping sickness.
Trypanosoma cruzi: Hemoflagellate that causes Chaga’s disease, a
cardiovascular disease common in Texas and Latin America.
Medically Important Protozoa (Continued)
2. Apicomplexans (Phylum Apicomplexa)
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Not motile in their mature form.
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Obligate intracellular parasites.
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Have specialized organelles at tip (apex) of cells that
penetrate host tissues.
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Complex life cycles. May have more than one host.
Definitive host: Harbors sexually reproducing form.
Intermediate host: In which asexual reproduction
occurs.
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Important Protozoa (Continued)
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2. Apicomplexans (Phylum Apicomplexa)
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Important pathogens:
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Plasmodium vivax and falciparum: Cause malaria in humans
(intermediate host).
Initially treated with quinine, drug resistance is a major problem
today.
Major cause of worldwide mortality: Kill 3 million people/year
and infect 500 million.
Transmitted by Anopheles mosquito (definitive host).
DDT was used extensively in 1960s in an attempt to eradicate the
mosquito vector.
Successful vaccine not available yet.
Life Cycle of Plasmodium spp. the
Infectious Agent of Malaria
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Important Protozoa (Continued)
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2. Apicomplexans (Phylum Apicomplexa)
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Important pathogens:
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Toxoplasma gondii: Causes toxoplasmosis in humans. Causes
blindness and lymphatic infections in adults. Dangerous to
pregnant women, causes severe neurological defects in unborn
children. Cats are part of life cycle, oocysts excreted in feces.
Contact with infected feces or meat are means of transmission.
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Cryptosporidium: Causes respiratory and gallbladder infections
in immunosuppressed individuals. Found in intestines of
mammals and water. Major cause of death in AIDS patients.
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Cyclospora cayetensis: New parasite (1996) caused diarrhea
associated with raspberries.
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Important Protozoa (Continued)
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3. Ciliates (Phylum Ciliophora)
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Move and obtain food using cilia.
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Only known human pathogen is Balantidium coli, which
causes a severe intestinal infection in pigs and humans.
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4. Microsporans (Phylum Mycrospora)
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Obligate intracellular parasites, lack mitochondria and
microtubules.
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Discovered in 1984 to cause chronic diarrhea and
conjunctivitis, mainly in AIDS patients.
Paramecium caudatum is a Ciliated Protozoan
Conjugation Between Opposite Mating Strains
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HELMINTHS (WORMS)
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Characteristics
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Eukaryotic, multicellular animals that usually have
digestive, circulatory, nervous, excretory, and
reproductive systems.
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Worms with bilateral symmetry, head and tail, and tissue
differentiation (endoderm, mesoderm, and ectoderm).
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Parasitic helminths spend most or all of their lives in host
and usually have the following specializations:
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May lack a digestive system. Absorb nutrients from host’s food,
body fluids, or tissues.
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Have a reduced nervous system.
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Means of locomotion is reduced or absent.
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Complex reproductive system. Individuals produce many eggs
that can infect another host.
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HELMINTHS (Continued)
Two main groups (phyla)
Platyhelminths (Flatworms)
Nematoda (Roundworms)
Life Cycle
Extremely complex
Intermediate hosts harbor larval (developmental) stage.
Definitive host harbors adult stage.
Sexual reproduction strategies:
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Dioecious: Male and female reproductive organs are found in
separate individuals.
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Monoecious (Hermaphroditic): One animal has both male and
female sex organs. Most hermaphrodites copulate with other
animals, a few copulate with themselves.
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HELMINTHS (Continued)
I. Platyhelminths (Flatworms)
Flattened from front to back.
Include:
1. Trematodes or Flukes
Leaf shaped bodies
Ventral and oral suckers for attachment and sucking
fluids from host.
Some can absorb nutrients through their cuticle.
Named for host tissues in which adult lives.
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Blood Fluke (Schistosoma spp.): Cause schistosomiasis which
affects over 400,000 immigrants in U.S. and 200 million people
worldwide.
Cause damage to blood vessels, liver, and many other organs.
Live in waters contaminated with feces, burrow through skin of
human and enter the circulatory system, particularly abdominal
and pelvic veins.
Free-Living Flatworm
Planaria
Life Cycle of Blood Fluke
(Schistosoma)
VI. HELMINTHS (Continued)
I. Platyhelminths (Flatworms)
1. Trematodes or Flukes
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Asian Liver Fluke (Clonorchis sinensis): Infests gallbladder, bile
ducts, pancreatic ducts, causes biliary cirrhosis and jaundice.
Cannot be transmitted in U.S. because intermediate hosts are not
available.
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Lung Fluke (Paragonius westermani): Lives in bronchioles of
humans and other animals. 12 mm long. Infection from eating
undercooked crayfish.
Asian Liver Fluke (Clonorchis sinensis)
Source: http://www.biosci.ohio-state.edu/~parasite/a-h.html
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HELMINTHS (Continued)
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I. Platyhelminths (Flatworms)
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2. Cestodes or Tapeworms
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Long flat bodies
Intestinal parasites
Lack a digestive system, absorb food through cuticle.
Body Organization:
Head or scolex has suckers for attachment.
Body is made up of segments called proglottids.
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Each proglottid has both male and female reproductive organs.
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Proglottids farthest from head are mature and contain many
fertilized eggs.
Cestode (Tapeworm) Body Structure:
Scolex and Proglottids
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HELMINTHS (Continued)
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I. Platyhelminths (Flatworms)
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Cestodes or Tapeworms (Continued)
Parasitic human tapeworms:
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Beef Tapeworm (Taenia saginata): Human is definitive host.
Can reach up to 6 meters in length, scolex is 2 mm long with
hundreds of proglottids. Infection occurs by ingestion of
contaminated, undercooked beef (“measly beef”).
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Pork Tapeworm (Taenia solium): Human is definitive host.
Infection can occur from eating infected undercooked pork
(rare in the U.S.) or from human to human contact.
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Echinococcus granulosus: Dogs and coyotes are definitive
hosts. Humans may become infected by contact with dog feces
or saliva.
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HELMINTHS (Continued)
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II. Nematodes (Roundworms)
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Cylindrical body tapered at each end.
Have a complete digestive system: mouth, intestine, and
anus.
Body is covered by tough cuticle that resists drying and
crushing.
Most species are dioecious: separate males and females.
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Males are smaller than females and have one or two spicules on
posterior end.
Over 90,000 known species. Most are free-living. Only
about 50 are human parasites.
Life cycle of parasitic nematodes is simpler than that of
flatworms.
Infections can be caused by eggs or larvae.
Comparison of Body Organization of Flatworms,
Roundworms, and Earthworms
Flatworm
Roundworm
Earthworm
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II. Nematodes (Roundworms) Continued
Infectious eggs
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Pinworm (Enterobius vermicularis): Spends entire life in human
host. Adults live in large intestine. Female lays eggs in perianal
region which causes itching. Up to 90% of children are infected
through contaminated clothes or bedding. Infection usually
disappears after a few years.
Ascaris (Ascaris lumbricoides): Large nematode, up to 30 cm.
Dioecious with sexual dimorphism. Live in small intestines of
humans, horses, and pigs. Eggs can survive in soil for long time.
Infectious larvae
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Adult Hookworm (Necator americanus): Live in small intestine of
humans, eggs are excreted in feces. Enter host by penetrating
skin. Enters bloodstream, travels to lungs, swallowed in sputum.
Avoided by wearing shoes.
Trichinosis (Trichinella spiralis): Reproduce sexually in small
intestine of humans. Obtained from eating undercooked pork.
Larvae enter blood vessels and form cysts throughout body.
Anisakines (Wriggly worms): Infected fish and squid. Killed by
freezing and cooking.
Pinworm (Enterobius vermicularis)
Source: http://www.biosci.ohio-state.edu/~parasite/a-h.html
Pinworm Eggs (Enterobius vermicularis)
Source: http://www.biosci.ohio-state.edu/~parasite/a-h.html
Ascaris (Ascaris lumbricoides)
Source: http://www.biosci.ohio-state.edu/~parasite/a-h.html
Head of Ascaris (Ascaris lumbricoides)
Notice three lips characteristic of Ascaris
Source: www. soton.ac.uk/~djab/ascaris.html