Medically Important Protozoa Medically Important Protozoa 1. Amoeboflagellates 1. Amoeboflagellates (Phylum Sarcomastigophora)(Phylum Sarcomastigophora) Move using pseudopods (false feet) or flagella.Move using pseudopods (false feet) or flagella. A. A. AmoebasAmoebas (Subphylum Sarcodina) (Subphylum Sarcodina) Move by extending blunt, lobelike projections Move by extending blunt, lobelike projections

(pseudopods).(pseudopods). Amoebas engulf food with pseudopods and phagocytize it.Amoebas engulf food with pseudopods and phagocytize it. Several species cause amoebic dysenteries of varying Several species cause amoebic dysenteries of varying

degrees of severity.degrees of severity. Entamoeba hystolyticaEntamoeba hystolytica:: Feeds on red blood cells. Produces Feeds on red blood cells. Produces

dysentery and extraintestinal cysts.dysentery and extraintestinal cysts. Dientamoeba fragilisDientamoeba fragilis:: Found in 4% of humans. Usually Found in 4% of humans. Usually

commensal. Can cause chronic, mild diarrhea.commensal. Can cause chronic, mild diarrhea. Other diseases include:Other diseases include:

Meningoencephalitis:Meningoencephalitis: Caused by Caused by Naegleria fowleriNaegleria fowleri.. Penetrate Penetrate nasal mucosa of swimmers in warm waters. Mortality rate nasal mucosa of swimmers in warm waters. Mortality rate almost 100%.almost 100%.

Keratitis:Keratitis: Caused by Caused by AcanthamoebaAcanthamoeba. Can cause blindness. . Can cause blindness. Associated with use of contact lenses.Associated with use of contact lenses.

B. B. FlagellatesFlagellates (Subphylum Mastigophora) (Subphylum Mastigophora) Move by one or more whiplike flagella. Some parasitic Move by one or more whiplike flagella. Some parasitic

flagellates have up to eight flagella.flagellates have up to eight flagella. Most are spindle shaped with flagella projecting from Most are spindle shaped with flagella projecting from

anterior end.anterior end. Outer membrane is a tough pellicle. Food is ingested Outer membrane is a tough pellicle. Food is ingested

through an oral groove or cytosotome.through an oral groove or cytosotome. Important pathogens:Important pathogens:

Trichomonas vaginalisTrichomonas vaginalis: Causes genital and urinary infections. : Causes genital and urinary infections. Has undulating membrane. Lacks a cyst stage. Transmitted Has undulating membrane. Lacks a cyst stage. Transmitted sexually or by fomites.sexually or by fomites.

Giardia lambliaGiardia lamblia: Causes a persistent intestinal infection : Causes a persistent intestinal infection (giardiasis) with diarrhea, nausea, flatulence, and cramps. In (giardiasis) with diarrhea, nausea, flatulence, and cramps. In U.S. most common cause of waterborne diarrhea. About 7% of U.S. most common cause of waterborne diarrhea. About 7% of U.S. population are healthy carriers.U.S. population are healthy carriers.

Trypanosoma brucei gambienseTrypanosoma brucei gambiense: Hemoflagellate (blood parasite). : Hemoflagellate (blood parasite). Causes African sleeping sickness. Causes African sleeping sickness.

Trypanosoma cruziTrypanosoma cruzi: Hemoflagellate that causes Chaga’s disease, a : Hemoflagellate that causes Chaga’s disease, a cardiovascular disease common in Texas and Latin America.cardiovascular disease common in Texas and Latin America.

Medically Important Protozoa (Continued) Medically Important Protozoa (Continued)

2. Apicomplexans2. Apicomplexans (Phylum Apicomplexa) (Phylum Apicomplexa)

Not motile in their mature form.Not motile in their mature form.

Obligate intracellular parasites.Obligate intracellular parasites.

Have specialized organelles at tip (Have specialized organelles at tip (apexapex) of cells that ) of cells that

penetrate host tissues.penetrate host tissues.

Complex life cycles. May have more than one host. Complex life cycles. May have more than one host.

Definitive hostDefinitive host: Harbors sexually reproducing form. : Harbors sexually reproducing form.

Intermediate hostIntermediate host: In which asexual reproduction : In which asexual reproduction

occurs.occurs.

Medically Important Protozoa (Continued) Medically Important Protozoa (Continued) 2. Apicomplexans2. Apicomplexans (Phylum Apicomplexa) (Phylum Apicomplexa) Important pathogens:Important pathogens:

Plasmodium vivax Plasmodium vivax and and falciparumfalciparum:: Cause malaria in humans Cause malaria in humans

(intermediate host). (intermediate host).

Initially treated with quinine, drug resistance is a major problem Initially treated with quinine, drug resistance is a major problem

today. today.

Major cause of worldwide mortality: Kill 3 million people/year Major cause of worldwide mortality: Kill 3 million people/year

and infect 500 million.and infect 500 million.

Transmitted by Transmitted by AnophelesAnopheles mosquito (definitive host).mosquito (definitive host).

DDT was used extensively in 1960s in an attempt to eradicate the DDT was used extensively in 1960s in an attempt to eradicate the

mosquito vector.mosquito vector.

Successful vaccine not available yet.Successful vaccine not available yet.

Life Cycle of Plasmodium spp. the Infectious Agent of Malaria

Medically Important Protozoa (Continued) Medically Important Protozoa (Continued) 2. Apicomplexans2. Apicomplexans (Phylum Apicomplexa) (Phylum Apicomplexa) Important pathogens:Important pathogens:

Toxoplasma gondiiToxoplasma gondii:: Causes toxoplasmosis in humans. Causes Causes toxoplasmosis in humans. Causes

blindness and lymphatic infections in adults. Dangerous to blindness and lymphatic infections in adults. Dangerous to

pregnant women, causes severe neurological defects in unborn pregnant women, causes severe neurological defects in unborn

children. Cats are part of life cycle, oocysts excreted in feces. children. Cats are part of life cycle, oocysts excreted in feces.

Contact with infected feces or meat are means of transmission.Contact with infected feces or meat are means of transmission.

CryptosporidiumCryptosporidium: Causes respiratory and gallbladder infections : Causes respiratory and gallbladder infections

in immunosuppressed individuals. Found in intestines of in immunosuppressed individuals. Found in intestines of

mammals and water. Major cause of death in AIDS patients.mammals and water. Major cause of death in AIDS patients.

Cyclospora cayetensisCyclospora cayetensis:: New parasite (1996) caused diarrhea New parasite (1996) caused diarrhea

associated with raspberries.associated with raspberries.

Medically Important Protozoa (Continued) Medically Important Protozoa (Continued)

3. Ciliates3. Ciliates (Phylum Ciliophora) (Phylum Ciliophora)

Move and obtain food using cilia.Move and obtain food using cilia.

Only known human pathogen is Only known human pathogen is Balantidium coli, Balantidium coli, which which

causes a severe intestinal infection in pigs and humans. causes a severe intestinal infection in pigs and humans.

4. Microsporans4. Microsporans (Phylum Mycrospora) (Phylum Mycrospora)

Obligate intracellular parasites, lack mitochondria and Obligate intracellular parasites, lack mitochondria and

microtubules.microtubules.

Discovered in 1984 to cause chronic diarrhea and Discovered in 1984 to cause chronic diarrhea and

conjunctivitis, mainly in AIDS patients.conjunctivitis, mainly in AIDS patients.

Paramecium caudatum is a Ciliated ProtozoanConjugation Between Opposite Mating Strains

VI. VI. HELMINTHS (WORMS) HELMINTHS (WORMS) CharacteristicsCharacteristics Eukaryotic, multicellular animals that Eukaryotic, multicellular animals that usuallyusually have have

digestive, circulatory, nervous, excretory, and digestive, circulatory, nervous, excretory, and reproductive systems.reproductive systems.

Worms with bilateral symmetry, head and tail, and tissue Worms with bilateral symmetry, head and tail, and tissue differentiation (endoderm, mesoderm, and ectoderm).differentiation (endoderm, mesoderm, and ectoderm).

Parasitic helminthsParasitic helminths spend most or all of their lives in host spend most or all of their lives in host and usually have the following specializations:and usually have the following specializations: May lack a digestive systemMay lack a digestive system. Absorb nutrients from host’s food, . Absorb nutrients from host’s food,

body fluids, or tissues. body fluids, or tissues. Have a Have a reduced nervous systemreduced nervous system.. Means of locomotion is reduced or absent.Means of locomotion is reduced or absent. Complex reproductive system. Individuals produce many eggs Complex reproductive system. Individuals produce many eggs

that can infect another host. that can infect another host.

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued) Two main groups (phyla)Two main groups (phyla) Platyhelminths (Flatworms)Platyhelminths (Flatworms) Nematoda (Roundworms)Nematoda (Roundworms) Life CycleLife Cycle Extremely complexExtremely complex Intermediate hosts harbor larval (developmental) stage.Intermediate hosts harbor larval (developmental) stage. Definitive host harbors adult stage.Definitive host harbors adult stage. Sexual reproduction strategies:Sexual reproduction strategies:

DioeciousDioecious: Male and female reproductive organs are found in : Male and female reproductive organs are found in

separate individuals.separate individuals.

Monoecious (Hermaphroditic):Monoecious (Hermaphroditic): One animal has both male and One animal has both male and

female sex organs. Most hermaphrodites copulate with other female sex organs. Most hermaphrodites copulate with other

animals, a few copulate with themselves.animals, a few copulate with themselves.

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued) I. Platyhelminths (Flatworms)I. Platyhelminths (Flatworms) Flattened from front to back.Flattened from front to back. Include:Include: 1. Trematodes or Flukes1. Trematodes or Flukes Leaf shaped bodiesLeaf shaped bodies Ventral and oral suckers for attachment and sucking Ventral and oral suckers for attachment and sucking

fluids from host.fluids from host. Some can absorb nutrients through their Some can absorb nutrients through their cuticlecuticle.. Named for host tissues in which adult lives.Named for host tissues in which adult lives.

Blood Fluke Blood Fluke (Schistosoma spp.(Schistosoma spp.)):: Cause schistosomiasis which Cause schistosomiasis which affects over 400,000 immigrants in U.S. and 200 million people affects over 400,000 immigrants in U.S. and 200 million people worldwide.worldwide.Cause damage to blood vessels, liver, and many other organs.Cause damage to blood vessels, liver, and many other organs.Live in waters contaminated with feces, burrow through skin of Live in waters contaminated with feces, burrow through skin of human and enter the circulatory system, particularly abdominal human and enter the circulatory system, particularly abdominal and pelvic veins.and pelvic veins.

Free-Living Flatworm Life Cycle of Blood FlukePlanaria (Schistosoma)

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued)

I. Platyhelminths (Flatworms)I. Platyhelminths (Flatworms)

1. Trematodes or Flukes1. Trematodes or Flukes Asian Liver Fluke Asian Liver Fluke (Clonorchis sinensis(Clonorchis sinensis)):: Infests gallbladder, Infests gallbladder,

bile ducts, pancreatic ducts, causes biliary cirrhosis and jaundice. bile ducts, pancreatic ducts, causes biliary cirrhosis and jaundice.

Cannot be transmitted in U.S. because intermediate hosts are not Cannot be transmitted in U.S. because intermediate hosts are not

available.available.

Lung Fluke (Lung Fluke (Paragonius westermaniParagonius westermani):): Lives in bronchioles of Lives in bronchioles of

humans and other animals. 12 mm long. Infection from eating humans and other animals. 12 mm long. Infection from eating

undercooked crayfish.undercooked crayfish.

Asian Liver Fluke (Clonorchis sinensis)

Source: http://www.biosci.ohio-state.edu/~parasite/a-h.html

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued) I. Platyhelminths (Flatworms)I. Platyhelminths (Flatworms)

2. Cestodes or Tapeworms2. Cestodes or Tapeworms Long flat bodiesLong flat bodies Intestinal parasitesIntestinal parasites Lack a digestive system, absorb food through cuticle.Lack a digestive system, absorb food through cuticle. Body Organization:Body Organization: Head or Head or scolexscolex has suckers for attachment. has suckers for attachment. Body is made up of segments called Body is made up of segments called proglottidsproglottids. .

Each proglottid has both male and female reproductive organs.Each proglottid has both male and female reproductive organs.

Proglottids farthest from head are mature and contain many Proglottids farthest from head are mature and contain many

fertilized eggs.fertilized eggs.

Cestode (Tapeworm) Body Structure:Scolex and Proglottids

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued) I. Platyhelminths (Flatworms)I. Platyhelminths (Flatworms) Cestodes or Tapeworms (Continued)Cestodes or Tapeworms (Continued) Parasitic human tapeworms:Parasitic human tapeworms:

Beef Tapeworm Beef Tapeworm (Taenia saginata)(Taenia saginata):: Human is definitive host. Human is definitive host.

Can reach up to 6 meters in length, scolex is 2 mm long with Can reach up to 6 meters in length, scolex is 2 mm long with

hundreds of proglottids. Infection occurs by ingestion of hundreds of proglottids. Infection occurs by ingestion of

contaminated, undercooked beef (“measly beef”).contaminated, undercooked beef (“measly beef”).

Pork Tapeworm Pork Tapeworm (Taenia solium)(Taenia solium):: Human is definitive host. Human is definitive host.

Infection can occur from eating infected undercooked pork Infection can occur from eating infected undercooked pork

(rare in the U.S.) or from human to human contact.(rare in the U.S.) or from human to human contact.

Echinococcus granulosus:Echinococcus granulosus: Dogs and coyotes are definitive Dogs and coyotes are definitive

hosts. Humans may become infected by contact with dog feces hosts. Humans may become infected by contact with dog feces

or saliva.or saliva.

VI. VI. HELMINTHS (Continued) HELMINTHS (Continued) II. Nematodes (Roundworms)II. Nematodes (Roundworms) Cylindrical body tapered at each end.Cylindrical body tapered at each end. Have a Have a complete digestive systemcomplete digestive system: mouth, intestine, and : mouth, intestine, and

anus. anus. Body is covered by tough cuticle that resists drying and Body is covered by tough cuticle that resists drying and

crushing.crushing. Most species are Most species are dioeciousdioecious: separate males and females.: separate males and females.

Males are smaller than females and have one or two spicules on Males are smaller than females and have one or two spicules on posterior end.posterior end.

Over 90,000 known species. Most are free-living. Only Over 90,000 known species. Most are free-living. Only about 50 are human parasites.about 50 are human parasites.

Life cycle of parasitic nematodes is simpler than that of Life cycle of parasitic nematodes is simpler than that of flatworms.flatworms.

Infections can be caused by eggs or larvae.Infections can be caused by eggs or larvae.

Comparison of Body Organization of Flatworms, Roundworms, and Earthworms

Flatworm

Earthworm

Roundworm

II. Nematodes (Roundworms) ContinuedII. Nematodes (Roundworms) Continued Infectious eggsInfectious eggs

Pinworm (Pinworm (Enterobius vermicularis)Enterobius vermicularis):: Spends entire life in human Spends entire life in human host. Adults live in large intestine. Female lays eggs in perianal host. Adults live in large intestine. Female lays eggs in perianal region which causes itching. Up to 90% of children are infected region which causes itching. Up to 90% of children are infected through contaminated clothes or bedding. Infection usually through contaminated clothes or bedding. Infection usually disappears after a few years.disappears after a few years.

Ascaris (Ascaris (Ascaris lumbricoides)Ascaris lumbricoides):: Large nematode, up to 30 cm. Large nematode, up to 30 cm. Dioecious with sexual dimorphism. Live in small intestines of Dioecious with sexual dimorphism. Live in small intestines of humans, horses, and pigs. Eggs can survive in soil for long time.humans, horses, and pigs. Eggs can survive in soil for long time.

Infectious larvaeInfectious larvae Adult Hookworm (Adult Hookworm (Necator americanus):Necator americanus): Live in small intestine Live in small intestine

of humans, eggs are excreted in feces. Enter host by penetrating of humans, eggs are excreted in feces. Enter host by penetrating skin. Enters bloodstream, travels to lungs, swallowed in sputum. skin. Enters bloodstream, travels to lungs, swallowed in sputum. Avoided by wearing shoes.Avoided by wearing shoes.

Trichinosis (Trichinosis (Trichinella spiralis):Trichinella spiralis): Reproduce sexually in small Reproduce sexually in small intestine of humans. Obtained from eating undercooked pork. intestine of humans. Obtained from eating undercooked pork. Larvae enter blood vessels and form cysts throughout body.Larvae enter blood vessels and form cysts throughout body.

Anisakines (Wriggly worms):Anisakines (Wriggly worms): Infected fish and squid. Killed by Infected fish and squid. Killed by freezing and cooking.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 AscarisSource: www. soton.ac.uk/~djab/ascaris.html