Parasitology Overview

Pediculus humanus
- Characteristics: smaller pinchers, elongated body
Phthirus Pubis
- Commonly known as: pubic lice
- Characteristics: squat body
Pulex irritans
- Commonly known as: flea
Cimex Lectularis
- Commonly known as: bedbug
Dermacenter
- Commonly known as: ticks
Sarcoptes scabiei
- Commonly known as: mite
Reclusa and Mectans
- Commonly known as: black widow

E. vermicularis
- Commonly known as: pinworm
- Characteristics: jellybean shape, thin outer wall
Trichuris trichiura
- Commonly known as: whipworm
- Characteristics: polar plugs
Ascaris lumbricoides
- Characteristics: fertile is decorticated, infertile is mammillated with a bumpy outer edge
Hookworm
- Species: Necator americanus and Ancylostoma duodenale
- Characteristics: ova shell that doesn’t stain, has a clumpy inside
Strongyloides stercoralis
- Commonly known as: threadworm
- Characteristics: Rhabditiform with a short buccal cavity
Trichinella spiralis
- Characteristics: forms nurse cells
Dracunculus medinensis
- Commonly known as: Guinea worm; extracted by pulling out of the skin
Wuchereria bancrofti
- Characteristics: microfilariae in peripheral blood (PB), adult forms located in lymphatics

Hymenolepis nana
- Characteristics: hexacanth with polar filaments
Hymenolepis diminuta
- Characteristics: lacks polar filaments
Taenia spp.
  - T. solium
    - Characteristics: hexacanth embryo; gravid proglottid has less than 15 branches; armed scolex
  - T. saginata
    - Characteristics: thick ova wall with striations; more than 15 branches; unarmed scolex
Echinococcus granulosis
- Form cysts in organs with protoscolices
Diphyllobothrium latum
- Characteristics: large oval ova; no hexacanth embryo; operculum present; abopercular knob; features bothria sucking grooves; has a rosette uterus

Fasciola buski and Fasciola hepatica
- Characteristics: ellipsoidal large ova; thin shell; operculum but no abopercular knob
Clonorchis sinensis
- Commonly known as: Chinese liver fluke
- Characteristics: vase-shaped; shoulders present on either side of operculum
Paragonimus westermani
- Characteristics: ova ovoid; has flattened operculum shoulders
Schistosoma mansoni
- Characteristics: has large lateral spine
Schistosoma japonicum
- Characteristics: has small lateral spine
Schistosoma haematobium
- Characteristics: has terminal spine

Entamoeba histolytica / E. dispar
- Cyst: contains 1-4 nuclei with a central karyosome and round cigar chromatoidal bars
- Trophozoite: contains 1 nucleus with a central karyosome; identifies on ingested RBCs for histolytica
Entamoeba coli
- Cyst: contains 1-8 nuclei and an eccentric karyosome
- Trophozoite: contains 1 nucleus; may harbor ingested debris or bacteria
Endolimax nana
- Cyst: contains 1-4 nuclei and atypical karyosome with an inkblot nucleus
- Trophozoite: contains 1 nucleus, atypical karyosome (inkblot)
Iodamoeba buetschlii
- Cyst: contains 1 nucleus, atypical karyosome (inkblot), and large glycogen vacuole
- Trophozoite: contains 1 nucleus; atypical karyosome (inkblot) with vacuolated cytoplasm
Naegleria fowleri
- Characteristics: Trophs only found in humans; has 1 nucleus, inkblot, with vacuolated cytoplasm
Acanthamoeba
- Characteristics: cyst has a double wall and wrinkled appearance; Troph has an inkblot nucleus with sharp spiny cytoplasmic projections

Balantidium coli
- Cyst: has macro and micronucleus; kidney bean shape
- Trophozoite: contains kidney bean nucleus; vacuolated cytoplasm with cilia present

Giardia
- Cyst: contains 2-4 nuclei and 2-4 axonemes (central supportive structures) giving a face-like appearance
- Trophozoite: has pear/teardrop shape resembling a “monkey face”
Dientamoeba fragilis
- Trophozoite only found in humans; characterized by a fractured/fragmented karyosome; contains 2 nuclei and no flagella
Trichomonas vaginalis
- Trophozoite only; contains 4 anterior flagella and has a half-length undulating membrane
Trypanosoma brucei
- Characteristics: trypomastigotes found in humans in peripheral blood (PB), lymph, and cerebrospinal fluid (CSF); full-length undulating membrane, “S” shaped
Trypanosoma cruzi
- Characteristics: trypomastigotes found in PB; has a full-length undulating membrane, “C” shaped with a large kinetoplast posterior; amastigotes found in muscle tissues in macrophages
Leishmania
- Characteristics: only amastigotes found in humans; predominantly in tissue macrophages found in skin or organs

Plasmodium falciparum
- Trophozoite: has a small thin ring with 1-2 chromatin dots; presents with multiple rings in the same RBC
- Gametocyte: crescent or banana-shaped
Plasmodium malariae
  - Trophozoite: presents single rings with 1 chromatin dot; band/basket forms
  - Schizont: contains 6-12 merozoites around central hemazoin
  - Gametocyte: oval, round shapes
Plasmodium vivax
  - Trophozoite: presents with single thick rings with 1 chromatin dot; contains Schuffner’s dots
  - Schizont: contains 12-24 merozoites
  - Gametocyte: round shape, may contain hemazoin
Babesia
- Trophozoite: can have up to 5 present in RBC, with 1-3 chromatin dots; merozoites appear as Maltese cross; NO schizont or gametocyte forms
Toxoplasma gondii
- Tachyzoite: small crescent-shaped with a large nucleus; bradyzoites form encysted in tissues

OVA: detected in species such as E. vermicularis, T. trichiura, A. lumbricoides, Hookworm, H. nana, H. diminuta, Taenia spp., D. latum, F. buski/hepatica, C. sinensis, P. westermani, Schistosoma spp.
LARVAE: identified in S. stercoralis, T. spiralis
ADULT WORMS: detected in Dracunculus
MICROFILARIAE: identified in Bancrofti
GRAVID PROGLOTTID: present in D. latum, saginata, and solium
HYDATID CYST: found in E. granulosis
CYSTS: diagnosed in E. histolytica/dispar, E. coli, E. nana