This document summarizes several fungi, parasites, and protozoa that can infect humans. It describes key characteristics of pathogens like Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum, Coccidioides immitis, Schistosoma mansoni, Taenia species, Ascaris lumbricoides, Enterobius vermicularis, hookworms, Trichinella spiralis, Plasmodium species, Giardia intestinalis, Entamoeba histolytica, Trypanosoma cruzi, and Trichomonas vaginalis. For each organism, it outlines the infectious stage, transmission method, sites of infection in the body

1. Selected fungi,
parasitic helminths, and protozoa

2.  Opportunistic pathogen
 Attaches to human epithelial cells as a yeast
 Usually it requires pseudohyphae to invade deeper tissues
 Buds form a short
chain of cells called
a pseudohypha
Candida albicans

3. Pityriasis in a Caucasian patient
Pityriasis in an African-american
patient
Malassezia furfur and pityriasis versicolor

4. Malassezia furfur and pityriasis versicolor
 10% KOH,
glycerol, and
Parker ink
solution
 Diagnostic: Stained skin scrapings from patients reveal
thick-walled, round yeast cells that reproduce by budding,
and hyphae

5.  Encapsulated yeast
 Inhalation of dried,
contaminated
droppings
(pigeon/chicken)
 Cryptococcal
meningitis
Cryptococcus
neoformans

6. Dimorphic fungi
Histoplasma capsulatum
 Pathogenic dimorphic fungi and systemic mycoses (diseases caused by
fungi that can spread throughout the body)
 Endemic of North America
 Coccidioides immitis - Coccidioidomycosis
 Histoplasma capsulatum – Histoplasmosis
 Blastomyces dermatitidis - Blastomycosis

7.  Arthroconidia inhaled from soil
germinate in the alveoli
Coccidioides immitis causes coccidioidomycosis
 Diagnosis
Identification of spherules in
clinical specimens
 Mild respiratory symptoms
 More severe infections
involving
 Coughing up blood
 Pneumonia/Meningitis

8. Schistosoma mansoni
Blood fluke
 Flukes are given names
according to the tissue of
the definitive host in which
the adults lives
 Lung fluke
 Liver fluke
 Blood fluke
 Cause progressive damage
to tissues and organs
Trematodes

9. Schistosoma mansoni
Egg
 Eggs lodge in
tissues causing
damage to several
organs

10. Tapeworms - Cestodes
 Taenia saginata
 Taenia solium
 Ingestion of
undercooked measly
meat or
 Eggs that leads to
cysticercosis in
humans
 Diagnosis in clinical specimens
 Proglottids
 Eggs

11. Proglottid
Egg
Taenia species

12. Ascaris lumbricoides
Nematode-round worm
 Infects over one billion people worldwide
 Small intestine
 Feeds on partially digested foods
 Eggs excreted with feces can survive for long periods

13. Ascaris
lumbricoides

14. Ascaris
lumbricoides
Unfertilized egg
Fertilized egg
DPDX Parasite Image Library – University of South Carolina School of Medicine

15. Enterobius vermicularis (nematode)
Pinworm
Eggs infective for humans

16. Enterobius vermicularis
Eggs
 The female migrates to the anus to deposit eggs on the perianal
skin at night (Diagnosis: Graham sticky-tape method)

17. Hookworms (nematode)
 Necator americanus
 Ancylostoma duodenale
 Larvae infective for humans by penetrating the
host’s skin
 Live in the small intestine of humans
 Feed on blood and tissue leading to anemia

18. Ancylostoma duodenale
Necator americanus
 Clinical specimen:
Feces/Eggs
Fertilized egg

19. Trichinella spiralis
Larva
Cysts within muscles

20. Plasmodium
species cause
malaria
Ring-stage
Trophozoites within red
blood cells

21. Giardia intestinalis
Trophozoites
 Adheres to small intestine causing diarrhea
 Trophozoite is the feeding/growing stage
 Cyst is the survival stage
Diagnosis: identification of
cysts in feces

22.  Pathogenic amoeba
 Human intestine,
causes amebic
dysentery
 Ingestion of cysts
excreted in the feces
of infected person
 Presence of ingested red blood
cells is diagnostic of Entamoeba

23. Trypanosoma cruzi causes the Chagas’ disease
 Bloodsucking “kissing bug”

24. Trichomonas vaginalis
Protozoan transmitted
through sexual
intercourse

25. Worldwide Prevalence of
Helminthic Diseases