PROTOZOAN INFECTIONS

PROTOZOA

Single celled organisms

Anaerobic

Most are motile

Asexual & Sexual reproduction

Trophozoites= active stage

Cysts/Oocysts = Protective stage

Some require multiple hosts

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Apicomplexa

Motile via apical complex

collection of organelles & cytoskeletal components at apex producing a "gliding motility"

Intracellular, Acid fast

 

Ex: Plasmodium (Malaria)

 

Gregarines

(Cryptosporidium)

 

Coccidians

(Cyclospora caayetanensis, Cystoisospora belli,

Sarcocystis)

Amoeba

Motile via pseudopods

temporary cytoplasmic extensions that produce a "Crawling" motion

Ex: Entamoeba histolytica

Amebiasis 

Naelgeria fowleri

Flagellates

Motile via flagella

hair-like projections that cause

a "whip-like" motion

Ex: Giardia duodenalis

Trichomonas vaginalis

Ciliates

Motile via cilia

much smaller than flagella, move in unison to produce movement

Ex: Balantidium coli 

Blood & Tissue

Protozoans

 

Intracellular

  • Babesia microti 

    • Hemolytic disease

  • Toxoplasma gondii

    • Encephalitis (AIDS pts)

    • Congenital: chorioretinitis, Hydrocephalus, intracranial calcifications 

  • Leishmania

    • Cutaneous papules & ulcers

    • Visceral (kala azar) splenomegaly, hepatomegaly, aplastic BM

  • Trypanosomas cruzi

    • Chagas disease- "kissing bug", cardiomegaly, megacolon/esophagus

Extracellular

  • Trypanosomas brucei 

    • African sleeping sickness- tsetse fly, chancre, hemolymphatic, meningoencephalitic

 

Free Living Amoeba

  • Naegleria fowleri

    • Rapidly progressive meningoencephalitis; bad water

Apicomplexa

  • Plasmodium spp. (Malaria)

    • Anopheles mosquito (sexual reproduction), human host (asexual). Affects liver & RBCs -> acute fever due to RBC lysis (timing varies according to  species), Transmitted via transplant, vertical (mom to baby) or infected needle. Prevent with mosquito control, prophylactic drugs & lack of duffy Ag)

  • P. falciparum (Malignant tertian malaria- 48 hrs):

    • heavy parasitemia, Infects RBCs of all ages, No RBC distortion. Ring forms (usually at edge/periphery of RBC ("applique" pattern)), Multiple ring forms per RBC , no/rare shizonts, no Schuffner's dots, May see Maurer's clefts, banana/crescent shaped gametocytes present; 48 hr fever cycle - most severe clinically. Africa. NOTE: RBCs infected by P. falciparum trophozoites and schizonts stick to capillary endothelial cells, so they aren’t found in peripheral circulation like other Plasmodium spp are.​​

  • P. ovale (Benign tertian malaria- 48 hrs):

    • Infected immature RBCs are enlarged, distorted, oval RBCs with cytoplasmic extensions and Schuffner's dots, Multiple ring forms within a single RBC. <12 nuclei in schizonts; 48 hr fever cycle. Trophozoites are compact & may cause the RBC to have fimbrae & stippling. Dormant hypozoite form in liver (reactivation). Mild clinically

  • P. vivax (Benign tertian malaria- 48 hrs):

    • All stages seen in peripheral blood. Infected immature RBCs are large, distorted round RBCs with cytoplasmic extensions. Mature trophozoite has "amoeboid shape" & may contain Schuffer's dots on Giemsa stain. >12 nuclei in schizonts; 48 hr fever cycle; Dormant hypozoite form in liver (reactivation) . Moderate-severe clinically

  • P. malariae (Quartan malaria- 72 hrs):

    • Infected senescent (old) RBCs are normal size/shape, Schizonts can have rosette pattern. Trophozoites appear as "bands" across RBC forms, no Schuffner's dots; 72 hour fever cycle; moderate severity (Looks exactly like P. knowlesii)

  • P. knowlesii (Quotidian malaria- 24 hrs):

    • normal size RBCs, band forms, no Schuffner dots; 24 hour fever cycle, severe, potentially fatal clinically (same morphology as P. malariae)

GI     or    GU Tract Protozoans 

 

Amoeba

  • Entamoeba histolytica

    • Ingested cysts go to large intestine, trophozoites replicated & make cytotoxins causing flask shaped ulcers​, dysentery (bloody diarrhea), Liver abscess​​

Flagellates

  • Giardia duodenalis

    • Pear shaped, 2 nuclei (eyes), adhesion disk, Adheres to small intestinal villi, foul smelling diarrhea, malabsorption, developmental impairment

  • Trichomonas vaginalis

    • STD, trophozoites transmitted (STD), vaginitis, frothy discharge, urethritis, undulating membrane (modified 5th flagella), no cyst form

Ciliates

  • Balantidium coli

    • *ONLY ciliate known to infect humans, ingested cysts from pigs, trophozoites  (macronucleus & micronucleus) infect colon, invasive (bloody diarrhea + mucus), perforated colon, trophozoites & cysts in stool, Tx= tetracycline

Apicomplexa

  • Cryptosporidium (C. parvum & C. hominis)

    • Waterborne, resists disinfections, forms parasitophorous vacuoles in brush border of sm. int., watery diarrhea, oocysts shed in stool (survive a few days). Self ltd (healthy); severe diarrhea/dehydration, can go to biliary ducts, stomach, lungs (immcomp)

  • Cystoisospora belli

    • Tropical areas, Watery diarrhea, malabsorption, Tx= trimethoprim

  • Cyclospora cayetanensis

    • From bad water, fruits/veggies. Watery diarrhea (+/- blood/mucus), self ltd

  • Sarcocystis species

    • From pigs or cows, intestinal or muscular illness

 
 

Nematodes

(Roundworms)

Round & Coiled

Covered by an outer cuticle

Has definitive mouth & anus

Ex: Trichinella spiralis

Filariae

(Filariasis)

SHEATHED:

  • Wuchereria bancrofti (NO tail nuclei)

  • Loa loa (+ tail nuclei)

  • Bruga malayi (+ tail nuclei)

NON-SHEATHED:

  • Mansonella perstans (+tail nuclei)

  • Mansonella stretocerca (+tail nuclei)

  • Mansonella ozzardi (NO tail nuclei)

  • Oncocerca Volvulus (NO tail nuclei)

HELMINTHS

Helminths = Worms

Multicellular organisms + suckers

Anaerobic (adults)

Separate sexes (M/F) or  Hermaphrodite forms

Muscular motility 

Can be LARGE & cause obstruction

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Trematodes

(Flukes)

Ex: Paragonimus westermanni ("Lung fluke")

Leaf shaped, sucker at one end,

tegument, Hermaphrodite

Ex: Schistosoma

(S. haemotobium, S. japonica, S. mansoni)

Separate sexes- Female  (smaller) resides in male's gynecophoral canal (pea-shaped)

Others:

Fasciolopsis buski

Faciola hepatica

Clonorchis sinensis

Flatworms

Cestodes

(Tapeworms)

Covered in tough tegument

Has 2 suckers on one end

Hermaphrodites

Ex: Echinococcus granulosis

Diphyllobothrium latum

Taenia solium/ T. saginata

Hymenolepsis nana/ H. diminuta

H.nana is the most common tapeworm infxn in the US.

Mansonella (M. ozzardi, M. perstans, M. streptocerca)

  • M. perstans has nuclei that descend down the length of the tail; Serous cavity filariasis

  • M. streptocerca has nuclei that descend down the length of the tail; SubQ /tissue filariasis
  • M. ozzardi: does NOT have tail nuclei, Causes serous cavity filariasis

Onchocerca volvulus

  • Onchocerca volvulus does NOT have tail nuclei; Causes SubQ / tissue filariasis

(Scroll over to see notes)

COMMON HELMINTH    INFECTIONS

Blood & Tissue Infections

 

Nematodes  (Roundworms)

Wuchereria bancrofti & Bruga malayi

Oncocerca volvulus

Loa loa

Dracunculus medinensis

Trichinella spiralis

Toxocara canis, Toxocara catis & Baylisacaris

Gastrointestinal Infections

 

Nematodes  (Roundworms)

ENTER HOST AS EGGS- REMAIN IN GI TRACT

  • Trichuris trichiura ("Whipworm")

  • Enterobius vermicularis ("Pinworm")

ENTER HOST AS EGGS- EXIT GI TRACT (LARVAL STAGE)

  • Ascaris lumbricoides ("Roundworm")

ENTER HOST AS LARVAE - EXIT GI TRACT (LARVAL STAGE)

  • Ancylostoma ("Old World Hookworm")

  • Necatur americanus ("New World Hookworm")

  • Strongyloides stercoralis ("Threadworm")

 

OTHER WAYS TO CLASSIFY

THE GI NEMATODES

   

INTESTINAL ROUNDWORMS (NON-INVASIVE)

  • Strongyloides stercoralis (threadworm)

  • Ancylostoma duodenalis (hookworm)

  • Ascaris lumbricoides

  • Enterobius vermicularis (most common worm infection in US)

  • Necatur americanus (hookworm)

  • Trichuris triciura (whipworm)

INTESTINAL TISSUE (INVASIVE) NEMATODES

  • Trichinella spiralis

  • Dracunculus medinensis

 

ARTHROPODS

 

Arthropods= True/inherent parasites

Segmented bodies

Hard exoskeleton

May serve as vectors and/or

intermediate hosts for

other parasites

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Other Vectors

 

Fleas

Ticks

Mosquitoes

 

Mites

(Chelicerta/Arachnids)

Ex: Sarcoptes scabiei (Scabies)

Adult burrows into skin, has dorsal shell with 4 pairs of legs & long, bristle-like setae that project posteriorly. Causes intense itching

Lice

(Insecta)

Named for region of body they inhabit

 

Ex: Pediculus humanus humanus

Has 3 pairs of legs with claws

used to help grip the skin & hair.

Itching (think preschoolers)