PROTOZOAN INFECTIONS

PROTOZOA

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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

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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.

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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

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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)

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These posts contain high yield information collected from various educational resources including textbooks, journal articles, educational websites and more. They are intended for educational use only and should NOT be taken as medical advice. I strongly believe the spreading of knowledge and depth of learned information should be encouraged in today's society rather than coveted. Membership is required to view these posts  and should be used solely for educational purposes only.