Medical Parasitology

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Medical Parasitology

• Hugh B Fackrell

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Parasitic eukaryotes

• protozoa
• Platyhelminthes (flatworms)
• Trematodes (flukes)
• Nematodes (roundworms)
• Cestodes (tapeworms)
• arthropods

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protozoa

• most important in warmer climates
• do not elicit a strong antibody response (some
  exceptions)
• diagnosed by microscopic means
• no vaccines
• humans are intermediate hosts

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Protozoa - two forms

• Trophozoite
• active, growing - causes disease
• Cyst
• dormant, resistant form
• - increases survival of protozoa and extends
  transmission

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Intestinal Urogenital Protozoa

• Amebae
• Flagellates
• Ciliates
• Coccidia
• Microsporidia

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Amebae
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Sarcodina

• 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.

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Sacrodina treatment

• tetracycline diloxanide furoate.
• metronidazole.
• usually includes choloroquine.

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Infections by Free Living Amaeboe

• Naeglaria
• Acathamoeba

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Naegleria

• found in freshwater lakes or streams
• causes encephalitis in swimmers - can be fatal
  (rare).

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Acanthamoeba

• 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

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Flagellates
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Trichomoniasis Trichomonas vaginalis

• - 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.

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Blood Tissue Protozoa

• Plasmodium
• Babesia
• Toxoplasma
• Sacrocystis
• Pneumocystis
• Leishmania
• Trypanosoma

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Giardiasis Giardia lamblia

• 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.

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Mastigophora flagellates - cont

• 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

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Trypanosomiasis

• Trypanosoma brucei gambiense (African sleeping
  sickness).
• Trypanosoma brucei rhodesiense.
• South American sleeping sickness (T. cruzi).
• Chagas disease.
• reservoir in Africa cattle, swine wild
  animals.
• infected by the Tse Tse fly bite ???legion ?
  lymph nodes - become lodged and form a chronic
  infection ? CNS - produce sleeping sickness ?
  coma.
• Treatment suramin sodium and pentamidine.

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South American Sleeping Sickness

• 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.

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Leishmaniasis Sand flies

• a) cutaneous
• b) viscerotropuie (clinical note)
• 12 million cases
• fever, chills sometimes gastrointestinal
  involvement.
• bone marrow aspects - cultures also
  serodiagnostic techniques.

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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.
• infect red blood cells which burst - paroxysm
• chills, fever, headache, nausea and vomiting.
• Treatment
• choloroquine primaquine.
• prophylaxis in mosquito infested areas.
• Toxoplasmasis Toxoplasma gondii
• world wide, very common
• domestic cats infected by eating mice, birds or
  raw meat and contact with the feces of other
  cats.
• not a serious illness - vague symptoms, fever,
  weakness, respiratory, mononucleosus-like
• lymphadenopathy

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Pneumocystosis

• Pneumocystis
• Pneumocystis carinii - Thought to be a protozoan
  but recent RNA analysis has shown it to be a
  fungus.
• Infections occur world wide, if symptoms occur -
  mild respiratory. Childhood.
• Occurence
• Primarily AIDS
• Hospitalized infants who were premature and
  malnourished
• Elderly
• Cancer and organ transplant patients who are
  being treated with immunosuppressive drugs.

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Pneumocystosis cont.

• Respiratory Infection
• interstitial pneumonitis with plasma cell
  infiltrates
• Treatment
• Trimethoprim - sulfamethoxazole
• Aerosolized pentamidine (particularly for AIDS
  patients)
• Laboratory Diagnosis
• Sputum, lavage, Transbronchial aspirate, Brush
  biopsy, Open biopsy
• Microscopic - Stain appearance, Fluorescent
  antibody

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Sporozoa

• 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.
• infect red blood cells which burst - paroxysm
• chills, fever, headache, nausea and vomiting.
• Treatment
• choloroquine primaquine.
• prophylaxis in mosquito infested areas.
• Toxoplasmosis Toxoplasma gondii
• world wide, very common
• domestic cats infected by eating mice, birds or
  raw meat and contact with the feces of other
  cats.
• not a serious illness - vague symptoms, fever,
  weakness, respiratory, mononucleosus-like
• lymphadenopathy

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Nematodes Roundworms

• Pinworm
• Roundworm
• Ascaris
• Whipworm
• Hookworm
• Threadworm
• etc

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Coccidia

• Cryptosporidiosis
• Intestinal disease
• Zoonotic, and person-to-person
• Cryptosporidium
• - swallow oocyst - sporozoites released
• - penetrate the brush border of intestine
• mild self-limiting entercolitis watery diarrhea
  without blood.Remission - 10 days
• High risk veterinary personnel, homosexuals
• Immunocompromised - AIDS etc -50 stools per day

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Coccidia cont.

• Laboratory Diagnosis
• Fresh, or formalin-treated stool
• Microscopic - direct smear stain -
  fluorescent antibody
• Oocysts - concentrated from stool of persons with
  diarrhea
• Treatment
• Spiramycin in early stages of AIDS
• Restoration of fluid
• Prevention
• Contaminated water supplies treated with
  chlorination and filtration
• avoid high risk sexual activities

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flatworms (platyhelminthes)
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arthropods
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DONE!!!