The Protozoa

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The Protozoa
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Characteristics of Protozoa
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Protozoa contain typical eukaryotic organelles

• Mostly heterotrophic, few are autotrophic
• Size and cellular features
• Unicellular organisms
• Pellicle
• Food vacuole and lysosomes
• Contractile vacuole

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Diversity among Protozoa
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Most protozoa are heterotrophs

• Procuring nutrients mostly bacteria
• Heterotrophic and saprobic existence
• Trophozoite Motile stage
• Cyst dormant stage (resistant)
• Reproduction mostly asexual, some sexual

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Classification of Protozoa
Based on type of Locomotion
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Amoebas form pseudopodia

• Group Sarcodina (Rhizopoda)
• Movement by pseudopodia (False Feet)
• Radiolaria and foraminifera
• Acanthamoeba infections
• Entamoeba histolytica

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Flagellates move by one or more flagella

• Group Mastigophora
• Movement by flagella
• Euglena and photosynthesis Chloroplasts
• Mutualism in the gut of larger organisms
• Parasitism Giardia

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Ciliates have two types of nuclei

• Group Ciliophora
• Movement by cilia
• Complexity in Paramecium
• Conjugation Exchange of nuclei
• Cell structures Trichocysts for defense and
  contractile vacuole (water storage)

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Sexual Recombination in Paramecium
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Apicomplexans (Sporozoa) are obligate parasites
no free-living forms

• Absence of cilia and flagella
• Parasitic forms
• Sporozoite stage
• Merozoite stage
• Cyst stage

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Protozoal Diseases Caused By Amoebas and
Flagellates
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Amoebiasis is the second leading cause of death
from parasitic disease

• Entamoeba histolytica
• Worldwide incidence
• Cause of amoebic dysentery
• Transmission
• Disease progression
• Recurrence

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The Course of Amoebiasis Due to Entamoeba
histolytica
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Primary amoebic meningoencephalitis is a sudden
and deadly infection

• Naegleria fowleri
• Free-living in warm lake water
• Enter mucosa of the nose (Diving, swimming)
• Travel along the olfactory bulbs to brain
• Symptoms Encephalitis, meningitis, death in 95
  of individuals.

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Giardiasis occurs in an estimated5 percent of
American adults

• Giardia lamblia
• Transmission
• Mostly in day-care
• Also in hikers/campers
• Symptoms
• Diagnostic signs
• Treatment

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Trichomoniasis affects over 10 percent of
sexually active individuals

• Trichomonas vaginalis
• Transmission
• Symptoms in females and males
• Diagnosis
• Treatment
• Cool fact Feeds on
• N. gonorrhoeae

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Trypanosomiasis is two different
diseasesGeography, vector, and symptoms differ

• African sleeping sickness
• Trypanosoma brucei var gambiense
• Trypanosoma brucei var rhodesiense
• Vector Tsetse fly (Glossina spp.)
• Symptoms bouts of fever, sleeping, coma
• Treatment Arsenic based drugs

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• Chagas Disease
• American trypanosomiasis T. cruzi
• Vector Triatoma infestans and other species
• Symptoms Organ damage, heart, brain
• Treatment Available
• Antigenic changes in trypanosomes genetic

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Leishmaniasis is of two forms

• Leishmania tropica and L. donovani
• Transmission by Phlebotomus sandfly
• Types
• Visceral disease (kala-azar) 90 fatal
• Cutaneous disease (Bhagdad boil) mild
• Leishmania and transposons

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Protozoal Diseases Caused By Ciliates and
Apicomplexans (Sporozoa)
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Balantidiasis is contracted from water or food
contaminated with pig feces

• Balantidium coli
• The only known human ciliate parasite
• Symptoms diarrhea, ulceration, or asymptomatic??
• Treatment Flagyl (Metronidazole)

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Toxoplasmosis is one of the most common
infectious diseases

• Toxoplasma gondii
• Cyst (and Oocyst) and Trophozoite forms
• Transmission cats, beef
• Symptoms systemic illness
• Diagnosis trophozoites in blood or tissue
• Congenital risk (TORCH)
• Treatment Sulfonamides
• Risk in persons with AIDS

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The Cycle of Toxoplasmosis in Nature
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Malaria caused by 4 different species

• Worldwide incidence (300 500 million)
• Plasmodium species
• P. vivax, P. ovale, P. malariae, and P.
  falciparum
• Transmission by Anopheles mosquito
• Three stages
• Merozoite, Sporozoite, and Gametocyte

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Malaria (continued)

• Anopheles mosquito acquires gametocyte from blood
  meal, transform to sporozoites
• Mosquito transfers sporozoites to human, which
  migrate to the liver
• Each sporozoite trasforms to 25,000 merozoites
  and go to infect RBCs in blood
• Symptoms
• Variable with species anemia, brain, kidneys,
  and heart failure

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Malaria (continued)

• Treatment Quinine was used in 1640
• Now, resistance has developed for many drugs
• Chloroquine, Mefloquine (prophylaxis)
• No vaccine due to gene shuffling (150 genes)
• Methods of control DDT, TV, and AC

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The Malaria Cycle
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Cryptosporidiosis (My Favorite Parasite)

• Cryptosporidium parvum, Cryptosporidium coccidi
• History Identified in mice in 1909
• First official human case in 1976
• Became more prevalent in 1980s (AIDS)
• Cysts are the infectious stage (F-O route)
• Sporozoites are in the intestinal tissue
• Found in over 50 species of animals including
  cows, horses, birds, and snakes

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C. parvum
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Cryptosporidium Life Cycle
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Cryptosporidiosis (continued)

• Symptoms Flu-like, profuse watery diarrhea,
  dehydration, and emaciation
• Prevalent in day-care centers
• Major outbreak in Milwaukee in 1993, with 400,000
  cases and over 100 deaths
• Occurrence in persons with AIDS was a major
  cause of death no medication then
• Now Nitazoxanide
• Diagnosis Acid-fast stain, IFA, PCR, ELISA

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Cyclosporiasis Another story in Houston

• Cyclospora cayetanensis
• Originally thought to be Blue Green Algae
• Identified in Nepal and South America
• Once called the BIG Cryptosporidium
• Symptoms Diarrhea, Cramps, Vomiting
• Can recur even after successful treament
• Transmission F-O route, mainly fresh produce,
  possible close contact
• Diagnosis Important because of Rx

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