Protozoa
I. General characteristics
A. Kingdom Protista - Single celled - animal-like
B. Heterotrophic & Free-living
C. Cell anatomy
D. Life forms
1. Trophozoite - feeding form, often motile
2. Cyst = dormant highly resistant
E. Reproduction - generally asexual by mitosis, some sexual
F. Classified by locomotion
1.Class Sarcodina - amoeboid-like -pseudopodia
a. Entamoeba histolytica
b. Naegleria fowleri
2. Class Mastigophora - flagellated
a. Giardia lamblia
b. Trichomoniasis
c. Trypanosomiasis - sleeping sickness & Chaga's disease
d. Leishmaniasis
3. Class Ciliophora - ciliates
4. Class Sporozoa -
a. Toxoplasma
b. Malaria
c. Cryptosporidiosis
d. Isospora
e. Pneumocystis
II. Sexually transmitted Protozoal Infection
A. Trichomoniasis
1. Biology - flagellate, no cyst
2. Pathogenicity - motility, non-invasive
3. Disease - asymptomatic in men, severe vaginal itching and foul smelling discharge in women
4. Treatment - Metronidiazole (flagyl)
III. Food and waterborne Protozoal Transmission
A. Amoebiasis
1. Biology - Entamoeba histolytica - cyst forming.
2. Pathogenicity - invasive, destroy tissue, invade
3. Disease - diarrhea, lesions, abscesses - 4% of U.S infected; 10% of world
4. Treatment - Metronidazole
5. Prevention - potable water, anti-protozoal treatment of food
(Note Naegleria fowleri = waterborne, nasal entry--> meningitis)
B. Giardiasis - most common in the U.S.
1. Biology -
a. cyst forming, flagellate
b. suckers
2. Pathogenicity
a. survives in duodenum
b. motile, suckers, flat shape
c. can survive 2 weeks under fingers nails; carriers
d. Russian giardia
3. Disease
a. wild mammals are reservoir
b. cyst is infective
c. nausea, cramps, fatty foods, flatulence, foul green watery diarrhea
4. Treatment
a. Metronidazole (flagyl)
b. Quinacrine (Atabrine) (psychoses)
5. Prevention
a. treated water (boiled, iodine, chlorine?)
b. potable water
C. Cryptosporidia, Isospora - animal reservoir; found in immunosuppressed people, treated with furizolidine
D. Toxoplasmosis
1. Biology
a. small sporozoan
b. spread in cats and grazing animals
2. Pathology
a. invades cells - intracellular parasite
b. nervous and muscles tissue
3. Disease
a. contact with cat litter\ raw meat
b. fever and malaise- flu-like - subclinical
c. immunosuppressed - lesions in retina, brain and other organs
d. pregnancy - transplacental infections = neurological damage, spontaneous abortion
4. Treatment
a. pyrimethamine plus sulfadiazine
5. Prevention
a. cat litter care
b. well cooked meats
IV. Arthropodborne Protozoal Infections
A. Malaria
1. Biology
a. Plasmodium sp. - P. vivax, P. malariae, P. ovale, P. falciparum
b. Sporozoan - complex life cycle
c. Intracellular parasite
d. over 500 million infected- one of the world's greatest public health problems
2. Pathogenicity
a. Invades blood - travels to organs
b. lysis of blood cells = chills and fever
c. cycle depends on species
d. Plasmodium falciparum = cerebral malaria
3. Disease
a. mosquito - rbc - reproduces - lysis cell
b. see life cycle
c. Cell lysis = malaria attack
4. Treatment
a. Quinine kills active stage
b. Primaquine and Chloroquine - active against dormant stages- Prophylaxis
c. Fansidar and Dapsone
d. Resistant Strains
5. Prevention
a. Mosquito - Anopheles
b. DDT, bug spray, mosquito netting
c. Sickle cell anemics have some resistance
B. Trypanosomiasis
1. Biology
a. Trypanosoma sp. -
b. endemic to South America - Chagas disease (Kissing bug)
and Africa - Sleeping sickness (Tsetse fly - Glossinia)
c. Flagellate
2. Pathology
a. transmitted by bite of fly
3. Disease -
a. Sleeping sickness - painful bite site - blood stream - fever, headaches, wasting, brain - coma death
b. Chaga's Disease - widespread tissue damage, especially in heart, sometimes reach brain
4. Treatment - none with good response - suramin
5. Prevention - control vector
C. Leishmaniasis
1. Biology
a. flagellate
b. associated with sandfly - Phlebotomas
2. Pathology
a. cutaneous - Oriental sore
b. visceral - "Kala-azar"
3. Disease
a. sore at site of bite and scarring
b. visceral = fever, emaciation, anemia, secondary infections
4. Treatment - antimony
5. Prevention
a. Sandflies
b. Vaccination
6. Present epidemic in Central Asia (16 cases in desert storm)
Multicellular Parasites
I. Kingdom Animalia
A. Organisms ; Phylum Platyhelminthes - flatworms
Phylum Nematoda - round worms
Phylum Arthropoda - insects
B. Large macroscopic organisms
C. Diagnosis - ova in clinical material
D. Cinical material- preserved, extracted, microscopic exam
E. Most worm infections via 5 F's and food or water related
II. Phylum Platyhelminthes - Flatworms - hermaphroditic
A. Tapeworms -
1. Biology
a. Scolex - with hooks and or suckers
b. Proglottid - contains reproductive organs
c. loss of advanced anatomy
d. increase in reproductive capabilities
e. Various causative organisms
Taenia saginata - beef tapeworm
T. solium - pork
Diphyllobothrium latum - fish tapeworm
Hymenolepis nana - dwarf tapeworm
Echinococcus - dog
f. Infect nearly all mammals, but require specific hosts (usually 2)
2. Pathology
a. does not cause widespread emaciation
3. Disease
a. mild diarrhea
b. proglottid = seen in feces
c. anemia
d. ova found in feces
4. Treatment -
a. Niclosamide
b. Mebendazole
5. Prevention - well cooked meat, animal contact
B. Flukes -
1.Biology
a. Schistosoma (S. mansoni, S. haematobium, S. japonicum)
b. Require intermediate and definitive hosts
c. Infecting blood vessels or liver
d. Males are large attach to vessel, females live inside fold of adult male body
2. Disease -
a. larvae - Enter through piercing the skin
b. go to blood vessels
c. blockage and allergic response
d. Cancer and secondary infections
3. Treatment - antimony
4. Prevention - control of snails and human feces
II. Nematodes - Roundworms - 2 separate sexes
A. Pinworm
1.Biology - Enterobious vermicularis
a. roundworm- infects colon
b. most common infection in U.S.
c. ova in dust of classrooms
2. Pathogenicity
a. large #'s
3. Disease
a. itching, eggs around rectum at night
b. diagnosis by scotch tape technique
4. Treatment
a. Mebendazole (1 tablet)
5. Prevention - hygiene
C. Trichinosis
1. Biology
a. roundworm - small -
b. infested pork - Instituted FDA -meat inspection
c. infests muscle tissue
d. pigs consume infected feces
2. Pathogenicity
a. migrates to muscles , encysts, calcium
3. Disease
a. muscle pain
b. hemorrhaging, swelling, allergic reactions, paralysis
4. Treatment - Mebendazole & steroids
5. Prevention
a. meat inspection
b. thoroughly cook meat
D. Ascaris -
1. Biology
a. Ascaris lumbricoides -
b. most prevalent multicellular parasitic infection
c. night soil = source
2. Disease
a. ova consumed or inhaled
b. hatch - larvae pass into blood
c. migrate through lungs
d. coughed up and swallowed - adults grow in intestines
e. load dependent - may cause blockage
f. ova in feces
3. Treatment -
a. mebendazole
b. piperazine
E. Guinea worm - Dracunculus medinensis - transmitted through microscopic copepods in water - migrates to skin and grows - allergic reaction- skin ulcer - metronidazole - mebendazole
F. Arthropodborne helminth infections
1. Filariasis - transmitted by mosquito, worms invade lymph vessels, causing inflammation, damage and inability to recycle fluid. Swelling occurs = elephantiasis
2. Loa-loa = fly bite transmits filarial worm that infects eye, causing blindness
G. Contact infections
1. Hookworm - worm attaches by means of hook - invades via larvae through bare feet. Migrate to intestine. Load dependent. Ova in feces. May cause anemia
III.
Arthropods1. mosquitos - transmit - malaria, encephalitis, Dengue fever, yellow fever
2. ticks - Lyme disease, babesiosis, Rocky Mountain spotted fever, relapsing fever, spotted fever
3. Fleas- typhus, plague, tularemia
4. Flies - sleeping sickness, trypanosomiasis
1. Lice - head and body
2. Mites - scabies
3. Fleas, flies, etc.