Parasitology Objectives

Recall foundational principles of parasitology

the study of host-parasite relationships, where one organism (parasite) lives in or on another (host), deriving nutrients at the host's expense.

Compare and contrast Intermediate and definitive host as it relates to parasites

Intermediate Host

• Suport immature, larval, or asexual development stages

Definitive Host

• harbor the adult, sexually mature stage of a parasite where sexual reproduction occurs

Discuss the general lifecycle and reproductive phases of a parasite

Parasite lifecycles involve alternating between parasitic stages (feeding/growth inside a host) and free-living or transmission stages (outside the host). They are classified as direct (one host) or indirect (multiple hosts),

Compare and contrast Sporogony and Schizogony as it relates to certain parasites

Sporogony

• is the maturation phase producing infective sporozoites outside the host (in vector)

Schizogony

• is rapid asexual multiplication creating merozoites inside the host (human)

Discuss the requirements and clinical indications for the following sample types:

1. Stool

   1. examine 3 specimens within 10 days (every other day preferred)

      1. Liquid - 30 minutes - no cysts

      2. Semisolid - An hour

      3. Formed 24 hours - no trophozites

   2. For Ova and parasites

2. Blood

   1. Thick smeal for concentration and thin smear for identification

   2. Paitent travel to endemic areas of concern

      Malarial or Babesia infections- collection in 8-12hr increments for 2-3 days

      Microfilariae Specific timing

3. Cellophane Tape Preparation

   1. detectetion of pinworms

• Collection in morning before bathing

• 3 days in a row

• Adhesive is placed over anal perineum area for several seconds then placed on a microscopic slide for examination

• Mostly in children  

4. Vaginal Wet Mount

• detection of trichomonas vaginalis

5. Urine

• detectiokn of schistosoma haematobium and trichmonas vaginalis

• Early morning or first void

• Respiratory Secretion

Describe the distinguishing characteristics of the following parasite Protozoan categories.

Amoebae

• Asexual binary fission

• Motile by pseudopods

• Two morphologic forms

  • Trophozoites - fragile state

  • Cysts - resistant state

Flagellates

• Motile by flagella in trophozoite form

• trophozoite stage is resistant stage

• Encystation and excystation occur

• two classes:

  • intestine species

  • extraintestinal species

Sporozoa

• no structures for mobility

• plasmodium - 5 humman pathogens

• babesia - 6 human pathogens

• ring form, developing trophozoite , immature schizont, mature schizont, microgametocyte, macrogametocyte

Ciliates

• 1 human pathogen - balantidium coli

• both forms

• motile by cilia projections

Coccidia

• intestinal andtissue dwelling

• sexual replication in human host

• asexual replication outside human host

• Most have intermediate host

  • cat, calf etc

State the preservatives used for fecal parasitology specimens

10% formalin

SAF

PVA

Modified PVA

Discuss the macroscopic and microscopic examination steps – including stains used - involved in identifying parasites from stool and blood specimens

Liquid or soft stools are more likely to contain trophozoites, while formed stools contain cysts

MAF stain

• USed for cryptosporidium, cystoisospora, and cyclospora

1. Define and differentiate the following parasitic structures commonly seen in protozoa and ciliates

Trophozoite

• replication stage in amoeba

Cyst

• resting or dormant -

Egg

• produced sexually or asexually by helminths

• nematodes, cestodes, and trematodes

Parabasal body

• small, granular mass found in certain flagellated protozoa

Chromatoid body

• aggregation of of ribosomes

• cyst stage of amobea

• e. histolytica - rounded blunt ends

• e coli - pointed, spilted ends

Glycogen vacuole

• protozoan cysts

• i. butschlii - known for this

Karyosome

• condensed chromatin bundles

Nucleus

Peripheral chromatin

Abopercular knob

• trematodes or flukes

• located on opposite end of the operculum

Kinetoplast

• kDNA - trypanosomatidae family

1. Identify the following microscopic findings in a stool specimen and correlate to patient status

1. White and red blood cells

2. Epithelial cells

3. Pollen granules

4. Vegetable fibers and plant cells

5. Yeast cells

6. Charcot-Leyden Crystals

1. Identify and discuss the lifecycle and clinical significance of the following intestinal parasites:

Entamoeba histolytica

• finger-like pseudopodia

• ingested red

Entamoeba dispar

Entamoeba coli    

• intestinal amebiasis

• 1-8 nuclie

Iodamoeba bütschlii

• non-pathogenic

• glycogen vacule

Endolimax nana    

• non-pathogenic

• flies and -

Acanthamoeba sp.

• contact lenses, csf common -

Blastocystis hominis

• vacuole centrally located

Giardia lamblia/intestinalis

• falling leaf

Dientamoeba fragilis

Chilomastix mesnili

Balantidium coli    

Cryptosporidium parvum

Cystoisospora belli

Cyclospora spp.

• transmission through lettuce rasberries an

Identify and discuss the lifecycle and clinical significance of Trichomonas vaginalis 

Identify and discuss the lifecycle and clinical significance of Naegleria fowleri 

Asymptomatic is colinised in nasal passage onmly

Found in warm bodies of water; lakes, streams, ponds, swimming pools, tap water

Transmission through inhalation through nose (dust or water)

Incidence higher in summer months

PAM- trophozoites invade brain, causing rapid tissue destruction

Death typically occurs in 3-6 days of symptom onset, successful treatment extremely rare

Only ameba with three morphologic forms- trophozoite, flagellate, cysts

Identify and discuss the lifecycle and clinical significance of Leishmania spp.

1. Identify and discuss the lifecycle and clinical significance of the following blood parasites:

   1. Plasmodium spp.

   2. Babesia spp.

1. Plasmodium spp.

2. Babesia spp.