Medical Parasitology

Protists

• unicellular

• diatoms-nonpathogenic

• dinoflagellates - few are pathogenic

Protozoal Diseases of Skin and Digestive/Urinary Tracts

Leishmania

• leishmaniasis

• transmitted via sandflies (Phlebotomus)

L. major

• cutaneous disease

L. donovani

• visceral disease (kala azar)

• Post-kala-azar dermal leishmaniasis (PKDL)

  • appears months-years later

  • goes from liver to skin

Giardiasis

• Giardia intestinalis

• contains cysts

  • similar to spores

  • infective stage

• trophozoites

  • disease cause stage

Cyclosporiasis

• Cyclospora cayetanesis

• Cyclosporidium parvum

• severe and often fatal in immunocompromised patients

Amoebiasis

• Entamoeba histolytica

• primary infection in intestinal tract

Trichomoniasis

• Trichomonas vaginalis

• only parasite that causes STD

• colpitis macularis: “strawberry cervix”

Citiates

• Balantidium coli

• only ciliate known to parasitize humans

• reservoir: animals, especially swine

Protistan Diseases of Blood and Nervous System

Phyla

• Plasmodium vivax

  • every 48 hrs (every 2nd day)

• Plasmodium ovale

  • every 48 hrs (every 2nd day)

• Plasmodium malariae

  • every 72 hrs (every 3nd day)

• Plasmodium falciparum

  • 36-48 hrs (every 2nd day)

  • black water (urine) fever

• Plasmodium spp: malaria

  • biggest killer in human history

  • female mosquitos

  • infects liver & rbc’s

  • enlarged liver & spleen

  • Paroxysm: recurrence/attack of disease

Babesia

• Babesia microti

• malaria-like disease

• transmitted via ticks

Toxoplasmosis

• Toxoplasma gondii

• primary host/reservoir- cats

• parasites may cross placenta

• TORCH antibody panel

Trypanosomiasis

1. Human African sleeping sickness

• T. Brucei

• transmitted via tsetse fly

• T. Brucei var. Gambiense

  • less virulent

  • slow progression

• T. Brucei var. rhodesiense

  • less virulent

  • quick progression

  • death w/i months

2. American trypanosomiasis (Chagas disease)

• T. crizi

• Reduvid bug

Amoebas

• Naegleria fowleri

• acute primary amebic meningoencephalitis (PAM)

Eukaryotic Microorganisms: Helminthic Diseases

1. Trematodes (Flukes)

Schistosomiasis

• Blood fluke

• cause of swimmer’s itch (Schistosoma dermatitidis)

• Intermediate Host: Snails

• Infective Stage: Cercaria

• final host: humans

Paragonimun westermani

• flukes travel to lungs

Fasciola hepatica

• parasites travel to the liver

2. Cestodes (Tapeworms)

• Structure:

  • Scolex: Head of the tapeworm

  • Proglottids: egg production and segmented body that can detach to spread eggs

• Common complication: pernicious anemia

• Examples:

  • Beef Tapeworm

    • Taenia saginata

  • Pork Tapeworm

    • Taenia solium

    • ingested: Cysticercus cellulosae

  • Fish Tapeworm

    • Diphyllobothrium latum

    • largest form

  • Dog tapeworm disease

    • Echinococcus granulosus

    • Hydatid cyst disease

    • humans can be intermediary host

  • Dwarf tapeworm

    • Hymenolepis nana

Roundworms (Phylum Nematoda)

• Ascariasis

  • Ascaris lumbricoides

  • females lay 200,000 eggs/day

• Trichinellosis

  • Trichinella spiralis

• Hookworms

  • Ancylostoma spp.

  • Nectator spp.

  • filariform larva- infective stage

• Pinworm (threadworm)

  • Enterobius vermicularis

  • female migrates to perianal region to lay eggs at night

• Guinea Worm

  • Dracunculus medinensis

• Whipworm

  • Trichuris trichiura

  • high worm burden leading to rectal prolapse

Filarial Worms

• Transmitted via flies/mosquitos

• L3- infective stage

• Filariasis

  • Wuchereria bancrofti

  • Brugia malayi

  • larvae infect lymphatic system

• River Blindness (Oncocercaiasis)

  • Ochocerca volvulus

  • transmitted via blackfly

• Eye worm: Loa loa

Arthropod Parasites

• scabies

  • Sarcoptes scabiei

• Crabs/pubic lice

  • Pthirus pubis

• Head lice

  • Pediculus humanus capitis