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Medical Parasitology
Hugh B Fackrell
Parasitic eukaryotes
protozoa
Platyhelminthes (flatworms)
Trematodes (flukes)
Nematodes (roundworms)
Cestodes (tapeworms)
arthropods
protozoa:
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most important in warmer climates
do not elicit a strong antibody response
(some exceptions)
diagnosed by microscopic means
no vaccines
humans are intermediate hosts
Protozoa - two forms
Trophozoite:
active, growing - causes disease
Cyst:
dormant, resistant form
- increases survival of protozoa and
extends transmission
Intestinal & Urogenital Protozoa
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Amebae
Flagellates
Ciliates
Coccidia
Microsporidia
Amebae
Sarcodina
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Sarcodina: Entamoeba histolytica
amoebiasis (amoebic dysentry).
only the cyst stage is infectious.
disseminated amoebiasis - abscesses in the
liver, can be fatal, diagnosed serologically.
person not infectious when gut contents
moving fast, cysts form when it slows
down.
Sacrodina: treatment
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tetracycline & diloxanide furoate.
metronidazole.
usually includes choloroquine.
Infections by
Free Living Amaeboe
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Naeglaria
• Acathamoeba
Naegleria:
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found in freshwater lakes or streams
causes encephalitis in swimmers - can be
fatal (rare).
Acanthamoeba:
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found in soil, fresh and brackish (1/2 salt)
water
ubiquitous
can infect contact lens not properly cared
for - infection of cornea, reduced vision.
enucleation: complete removel of the
eyeball
Flagellates
Trichomoniasis: Trichomonas
vaginalis
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- millions of cases
sexually transmitted - trophozoite inhabits
the vagina and urethra.
males have very little irritation.
female, vagina becomes alkaline, allows the
bacteria to overgrow that are usually
suppressed by acid - symptoms include
odor, discharge, itching and burning.
Treatment: metronidazole, Flagyl.
Blood & Tissue Protozoa
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Plasmodium
Babesia
Toxoplasma
Sacrocystis
Pneumocystis
Leishmania
Trypanosoma
Giardiasis: Giardia lamblia
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fecal/oral transmission.
the cyst form is very resistant to destruction.
infection of upper small instestine, can be
asymptomatic.
most common protozoal infection in the
U.S.
Mastigophora: flagellates - con’t
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Gastroenteritis:
diarrhea, dark, greasy, foul feces.
abdomenal discomform, flatulence,
anorexia, weight loss.
lasts two-three weeks followed by recovery.
chronic - intermittent diarrhea.
Transmission:
water - treated and untreated.
common in daycare centers
Trypanosomiasis:
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Trypanosoma brucei gambiense (African
sleeping sickness).
Trypanosoma brucei rhodesiense.
South American sleeping sickness (T.
cruzi).
Chaga’s disease.
reservoir in Africa: cattle, swine & wild
animals.
infected by the Tse Tse fly bite
legion
South American Sleeping
Sickness
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T. cruzi:
reservoir dogs, cats & wild animals.
vector reduvid bugs - defecate when biting introduce trypanosomes.
can be spread by hands from bite to eyes,
conjunctivitis.
no treatment.
Prevention: control insects.
Leishmaniasis: Sand flies
• a) cutaneous
• b) viscerotropuie (clinical note)
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12 million cases
fever, chills & sometimes gastrointestinal
involvement.
bone marrow aspects - cultures also
serodiagnostic techniques.
Malaria
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Plasmodium vivax, P. falciparum and P.
ovale.
100,000,000 cases
spread by Anopheles mosquito
1 million deaths per year in the tropics and
sub-tropics.
life cycle of protozoa in the mosquito and
the human control the transmission and the
disease.
Pneumocystosis
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Pneumocystis
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Pneumocystis carinii - Thought to be a
protozoan but recent RNA analysis has
shown it to be a fungus.
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Infections occur world wide, if symptoms
occur - mild respiratory. Childhood.
Pneumocystosis cont.
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Respiratory Infection
interstitial pneumonitis with plasma cell
infiltrates
Treatment
Trimethoprim - sulfamethoxazole
Aerosolized pentamidine (particularly for
Sporozoa
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Malaria: Plasmodium vivax, P. falciparum
and P. ovale.
100,000,000 cases
spread by Anopheles mosquito
1 million deaths per year in the tropics and
sub-tropics.
life cycle of protozoa in the mosquito and
the human control the transmission and the
disease.
Nematodes: Roundworms
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Pinworm
Roundworm
Ascaris
Whipworm
Hookworm
Threadworm
etc
Coccidia
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Cryptosporidiosis
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Intestinal disease
Zoonotic, and person-to-person
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Cryptosporidium
Coccidia cont.
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Laboratory Diagnosis
Fresh, or formalin-treated stool
Microscopic - direct smear stain
- fluorescent antibody
Oocysts - concentrated from stool of
persons with diarrhea
Treatment
flatworms (platyhelminthes)
arthropods
DONE!!!