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
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Babesia microti
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Hemolytic disease
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Toxoplasma gondii
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Encephalitis (AIDS pts)
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Congenital: chorioretinitis, Hydrocephalus, intracranial calcifications
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Leishmania
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Cutaneous papules & ulcers
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Visceral (kala azar) splenomegaly, hepatomegaly, aplastic BM
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Trypanosomas cruzi
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Chagas disease- "kissing bug", cardiomegaly, megacolon/esophagus
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Extracellular
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Trypanosomas brucei
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African sleeping sickness- tsetse fly, chancre, hemolymphatic, meningoencephalitic
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Free Living Amoeba
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Naegleria fowleri
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Rapidly progressive meningoencephalitis; bad water
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Apicomplexa
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Plasmodium spp. (Malaria)
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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)
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P. falciparum (Malignant tertian malaria- 48 hrs):
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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.
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P. ovale (Benign tertian malaria- 48 hrs):
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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
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P. vivax (Benign tertian malaria- 48 hrs):
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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
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P. malariae (Quartan malaria- 72 hrs):
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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)
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P. knowlesii (Quotidian malaria- 24 hrs):
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normal size RBCs, band forms, no Schuffner dots; 24 hour fever cycle, severe, potentially fatal clinically (same morphology as P. malariae)
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GI or GU Tract Protozoans
Amoeba
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Entamoeba histolytica
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Ingested cysts go to large intestine, trophozoites replicated & make cytotoxins causing flask shaped ulcers, dysentery (bloody diarrhea), Liver abscess
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Flagellates
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Giardia duodenalis
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Pear shaped, 2 nuclei (eyes), adhesion disk, Adheres to small intestinal villi, foul smelling diarrhea, malabsorption, developmental impairment
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Trichomonas vaginalis
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STD, trophozoites transmitted (STD), vaginitis, frothy discharge, urethritis, undulating membrane (modified 5th flagella), no cyst form
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Ciliates
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Balantidium coli
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*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
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Apicomplexa
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Cryptosporidium (C. parvum & C. hominis)
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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)
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Cystoisospora belli
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Tropical areas, Watery diarrhea, malabsorption, Tx= trimethoprim
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Cyclospora cayetanensis
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From bad water, fruits/veggies. Watery diarrhea (+/- blood/mucus), self ltd
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Sarcocystis species
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From pigs or cows, intestinal or muscular illness
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Nematodes
(Roundworms)
Round & Coiled
Covered by an outer cuticle
Has definitive mouth & anus
Ex: Trichinella spiralis
Filariae
(Filariasis)
SHEATHED:
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Wuchereria bancrofti (NO tail nuclei)
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Loa loa (+ tail nuclei)
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Bruga malayi (+ tail nuclei)
NON-SHEATHED:
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Mansonella perstans (+tail nuclei)
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Mansonella stretocerca (+tail nuclei)
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Mansonella ozzardi (NO tail nuclei)
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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)
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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
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M. ozzardi: does NOT have tail nuclei, Causes serous cavity filariasis
Onchocerca volvulus
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Onchocerca volvulus does NOT have tail nuclei; Causes SubQ / tissue filariasis
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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
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Trichuris trichiura ("Whipworm")
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Enterobius vermicularis ("Pinworm")
ENTER HOST AS EGGS- EXIT GI TRACT (LARVAL STAGE)
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Ascaris lumbricoides ("Roundworm")
ENTER HOST AS LARVAE - EXIT GI TRACT (LARVAL STAGE)
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Ancylostoma ("Old World Hookworm")
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Necatur americanus ("New World Hookworm")
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Strongyloides stercoralis ("Threadworm")
OTHER WAYS TO CLASSIFY
THE GI NEMATODES
INTESTINAL ROUNDWORMS (NON-INVASIVE)
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Strongyloides stercoralis (threadworm)
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Ancylostoma duodenalis (hookworm)
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Ascaris lumbricoides
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Enterobius vermicularis (most common worm infection in US)
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Necatur americanus (hookworm)
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Trichuris triciura (whipworm)
INTESTINAL TISSUE (INVASIVE) NEMATODES
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Trichinella spiralis
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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)