Selected fungi, parasitic helminths, and protozoa

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

Pityriasis in a Caucasian patient

Pityriasis in an African-american patient

Malassezia furfur and pityriasis versicolor

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

Encapsulated yeast

Inhalation of dried,

contaminated droppings (pigeon/chicken)

Cryptococcal meningitis

Cryptococcus neoformans

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

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

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

Schistosoma mansoni

Egg

Eggs lodge in tissues causing damage to several organs

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

Proglottid

Egg

Taenia species

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

Ascaris lumbricoides

Ascaris lumbricoides

Unfertilized egg

Fertilized egg

DPDX Parasite Image Library – University of South Carolina School of Medicine

Enterobius vermicularis (nematode) Pinworm

Eggs infective for humans

Enterobius vermicularis

Eggs

The female migrates to the anus to deposit eggs on the perianal skin at night (Diagnosis: Graham sticky-tape method)

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

Ancylostoma duodenale

Necator americanus

Clinical specimen: Feces/Eggs

Fertilized egg

Trichinella spiralis

Larva

Cysts within muscles

Plasmodium

species cause malaria

Ring-stage Trophozoites within red blood cells

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

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

Trypanosoma cruzi causes the Chagas’ disease

Bloodsucking “kissing bug”

Trichomonas vaginalis

Protozoan transmitted

through sexual intercourse

Worldwide Prevalence of Helminthic Diseases