Selected Fungal
and Protozoan Diseases
Updated Summer 2015
Jerald D. Hendrix
Properties of the Fungi
• Basic properties
▫ Single celled (yeast) or filamentous (molds; fleshy
fungi)
▫ Filaments are called hyphae (singular: hypha)
▫ Hyphae may be septate or nonseptate
(coenocytial)
▫ All are heterotrophic chemorganotrophs; none are
phototrophic
▫ Cell walls contain cellulose and may also contain
chitin
Properties of the Fungi
• The Chytridiomycetes
▫ Probably the deepest branching fungal group, motile sexual
spores
• The Zygomycetes
▫ Reproduces asexually by producing haploid spores at the end of
stalk-like sporangia
▫ Reproduces sexually when gametangia of opposite mating types
fuse (plasmogamy) resulting in a dikaryotic sexual spore; when
the spore finds favorable conditions, karyogamy and meiosis
occurs, forming haploid cells that grow into hyphae
▫ Industrially important genera include Mucor, Rhizomucor, and
Rhizopus
▫ Possibly related phylogenetically to microsporidia and
glomeromycetes – two groups of asexually reproducing parasitic
fungi
Properties of the Fungi
• The Ascomycetes (“Sac fungi”)
▫ Reproduce asexually by producing chains of
haploid spores at the end of aerial hyphae
▫ Reproduce sexually when gametangia of opposite
mating types fuse and form a diploid nucleus;
meiosis occurs immediately to produce forming
haploid ascospores; the ascospores are formed
within sacs called asci
▫ Important genera include Saccharomyces,
Neurospora, Sordaria, Morabella, Tuber,
Schizosaccharomyces, Candida, Aspergillus
Properties of the Fungi
• The Basidiomycetes (“club fungi”)
▫ Sexual spores are formed on club-shaped
structures called basidia
▫ Includes mushrooms and puffballs,
Phanerochaete chrysosporium (white rot, used in
bioremediation), Cryptococcus (important human
pathogen), and smut & rust diseases of plants
Fungal Diseases
A.
B.
C.
D.
E.
F.
Candidiasis
Dermatophytosis
Cryptococcosis
Histoplasmosis
Blastomycosis
Pneumocystosis
Candidiasis
• Cause: Candida albicans and several other
species of the genus Candida
▫ An ascomycete
▫ Grows as yeast or pseudohyphae, dependent on
cultural conditions (dimorphic)
▫ Very common normal flora in mouth, intestinal
tract, and vaginal tract
▫ Many cases due to antibiotic usage (decreased
bacterial flora to compete with Candida) and
compromised immunity (such as AIDS)
Candidiasis
• Symptoms
▫ Mucosal candidiasis: Oral candidiasis (thrush),
esophageal candidiasis, intestinal candidiasis,
candidal vulvovaginitis, candidal balanitis
▫ Cutaneous candidiasis and candidal
onychomycosis
▫ Systemic candidiasis: Candidal septecemia and
liver damage
Dermatophytosis
• Cause: Several genera of dermatophytic
fungi
▫ Trichophyton, an ascomycete
▫ Microsporum, an ascomycete
▫ Epidermophyton, an ascomycete
▫ Grow on skin, hair, nails
▫ Transmitted by contact with infected
persons or animals
Dermatophytosis
• Symptoms
▫ Tinea infections: Red, scaly or blister-like lesions;
often a raised red ring; “ringworm”
▫ Used together with Latin name of the body part:
 Tinea pedis
 Tinea corporis
 Tinea capitis
 Tinea barbae
 Tinea cruris
 Tinea unguium
Cryptococcosis
• Cryptococcus neoformans and Cryptococcus gattii
• A basidiomycete
• Spores in contaminated soil; esp. contaminated with
bird droppings
• Airborne to humans
• Gelatinous capsules resist phagocytosis
• Respiratory tract infections
• Occasional systemic infections involving brain &
meninges
Histoplasmosis
• Histoplasma capsulatum
• An ascomycete
• Airborne infection
• Transmitted by inhalation of spores in
contaminated soil
• Associated with chicken & bat droppings
• Respiratory tract symptoms; fever,
headache, cough, chest pains
Blastomycosis
• Blastomyces dermatitidis
• An ascomycete
• Associated with dusty soil & bird droppings
• Skin transmission: via cuts & abrasions
• Raised, wart-like lesions
• Airborne transmission: via inhalation of spores
• Respiratory tract symptoms
• Occasional internal infections with high
fatality rate
Pneumocystosis
• Pneumocystis jirovecii (formerly Pneumocystis
carinii)
• An ascomycete
• Transmitted by airborne contact
• Usually asymptomatic or with mild respiratory
symptoms
• Causes severe pneumonia in
immunocompromised persons
• A major secondary infection & cause of death in
AIDS patients
Properties of the Protozoa
• Cellular properties
▫ Eukaryotic microorganisms having animal-like
cells
▫ No cell walls
▫ Most have heterotrophic metabolisms
▫ A few protozoa (eg Euglena) are photosynthetic
Properties of the Protozoa
• Cellular properties (cont.)
▫ Many are free-living in soil or aquatic
environments; a few are parasitic
▫ Single-celled or simple colonial organization
▫ Classification based predominately on the
mechanism of motility
Properties of the Protozoa
• “Trophozoite” and “Cyst”
▫ Some protozoa go through different stages in their
life cycle.
▫ This is especially true of certain parasitic protozoa.
▫ Trophozoite: Actively growing and reproducing
stage
▫ Cyst: A dormant stage, enclosed in a resistant cyst
coat
Properties of the Protozoa
• Selected Protista
▫ Diplomonads and parabasalids





Unicellular & flagellated
Lack mitochondria and chloroplasts
Parasites
Giardia – a diplomonad; has mitosomes
Trichomonas – a parabasalid; parabasal body
supports golgi; no mitochndria but has
hydrogenosomes; unusually large genome, highly
repetitive, lacks introns but may encode around
60,000 genes (almost twice the number of humans)
Properties of the Protozoa
• Selected Protista (continued)
▫ Euglenozoans
 Unicellular, flagellated
 Trypanosoma and Leishmania, two genera of
kinetoplastids
 the kinetoplast is a mass of DNA within their single large
mitochondria
 Trypanosoma includes species of insect-borne parasitic
flagellates, including causes of sleeping sickness and Chargas
disease
 Euglena, a euglenid
 Photosynthetic with chloroplasts; can also live as
chemorganotrophs in the darkness and can feed on bacteria
via phagocytosis
Properties of the Protozoa
• Selected Protista (continued)
▫ Alveolates
 Characterized by alveoli – membranous sacks
located just underneath the plasma membrane;
function unknown
 Ciliates
 covered with cilia; oral groove; macronuclei and
micronuclei, conjugation, many host endosymbionts
 Paramecium – free-living ciliate
 Balantidium – parasitic
Properties of the Protozoa
• Selected Protista (continued)
▫ Alveolates (continued)
 Dinoflagellates
 Diverse group of freshwater and marine phototrophic
alveolates; part of the plankton
 Includes Gonyaulax, the “red tide” organism
 Apicomplexians
 Once known as the Sporozoa
 Nonmotile “adult” forms
 Contain apicoplasts (degenerated nonfunctional
chloroplasts) and likely evolved from red-tide dinoflagellates
 Sexually reproducing (meiosis and chromosome segregation)
 Different life cycle stages may require different host species
 Example: Plasmodium, cause of malaria
Properties of the Protozoa
• Selected Protista (continued)
▫ Stramenopiles
 Diatoms – another photorophic plantonic group
 Golden algae (chrysophytes) and brown algae
 Golden algae are mostly unicellular; some are colonial
 Brown algae (Fucus) are mostly multicellular; seaweed
 Oomycetes




Slime molds
Originally classified as fungi
Motile, flagellated sexual spores
Includes Phytophthora, cause of the potato blight
Properties of the Protozoa
• Selected Protista (continued)
▫ Cercozoans and Radiolarians
 Once classified as amoebas because of pseudopods
 Cercozoans
 Chlorarachniophytes: Both freshwater and marine;
“amoeba-like;” phototrophic; no test (shell)
 Foraminifera: Exclusively marine and form symetrical
tests of calcium carbonate; may also host algal
symbionts
 Radiolarians
 Also make calcium tests; typically lobed or spiked;
exclusively heterotrophic
Properties of the Protozoa
• Selected Protista (continued)
▫ Amoebozoa
 Gymnamoebas – free-living amoebas; unicellular with
pseudopod movement; genera Amoeba and Pelomyxa
 Entamoebas – parasitic, example Entamoeba hystolytica
that causes amoebic dysentery
▫ Slime molds
 Once classed as fungi
 Dictyostelium
 Life cycle that begins as amoeba that slime together,
aggregate, and form multicellular stalks (fruiting bodies)
Protozoan Diseases
A.
B.
C.
D.
E.
F.
G.
H.
Amebiasis
Primary Amebic Meningoencephalitis
Giardiasis
Trichomoniasis
Balantidiasis
Toxoplasmosis
Malaria
Cryptosporidiosis
Amebiasis
• Cause: Entamoeba histolytica
▫
▫
▫
▫
▫
A parasitic amoeba
Transmitted via contaminated food & water
Cysts are shed in the feces
When ingested: Excystation occurs in the intestine
Trophozoites grow & reproduce in the intestinal
tract
Amebiasis
• Symptoms
▫ Abdominal pain
▫ Little diarrhea but often blood in the stool
(“amebic dysentery”)
▫ Possibly of intestinal ulceration; perforation;
infection of internal organs such as liver & lungs
Primary Amebic Meningoencephalitis
• Cause: Naegleria fowleri
▫ A fresh water, free living ameba
▫ No cyst stage
▫ Several cases of infections in swimmers
• Transmission and Symptoms:
▫ Transmission through the nasal & sinus passages
▫ Infection of the brain & meninges
▫ Headaches; delirium; seizures
Giardiasis
• Cause: Giardia lamblia
▫ A flagellated diplomonad
▫ The trophozoite has four pairs of flagella & two
nuclei; giving it a face-like appearance
▫ Grows in the intestinal tract
▫ Cysts are shed in the feces
Giardiasis
• Transmission and Symptoms
▫
▫
▫
▫
▫
▫
Transmitted via contaminated water & food
Foul-smelling profuse diarrhea
Sometimes chronic
Often misdiagnosed
Diagnosis via microscopic examination
Enterotest capsule
Trichomoniasis
• Cause: Trichomonas vaginalis
▫ Flagellated parabasalid
▫ No cyst stage
• Transmission & Symptoms
▫
▫
▫
▫
Transmitted via sexual contact
Genital itching
Painful urination with a white, mucoid discharge
Occasional reduction of sperm count or erosion of
the cervix
Balantidiasis
• Cause: Balantidium coli
▫ Ciliated alveolate
▫ Trophozoites grow in the intestinal tract
▫ Cysts are shed in the feces and may remain
embedded in intestinal walls, causing chronic
infections
• Transmission & Symptoms
▫ Contaminated water & food
▫ Ulceration in intestines
▫ Profuse diarrhea
Toxoplasmosis
• Cause: Toxoplasma gondii
▫ Alveolate apicomplexian
▫ Both asexual & sexual stages
▫ Invasion of several areas of the body, including
internal organs & muscle tissue
▫ Possibly the most prevalent protozoan parasite of
humans
Toxoplasmosis
• Transmission & Symptoms
▫ Transmitted via eating contaminated meat
▫ Cysts are found in the meat, especially of grazing
animals such as cattle
▫ Cats can transmit the disease through their feces
▫ Lymph node swelling; flu-like symptoms
Toxoplasmosis
• Transmission & Symptoms (cont.)
▫ Generally mild in non-immunosuppressed
persons
▫ Severe infections in immunosuppressed persons
▫ Pregnant women are in danger of fetal damage or
miscarriage
Malaria
• Cause: Plasmodium species
▫ Alveolate apicomplexian
▫ Complex life cycle requiring two hosts: a mammal
(human) and the mosquito Anopheles
Malaria
• Transmission and Symptoms
▫ The asexual merozoite stage infects human blood
from the bite of a mosquito
▫ The parasite invades erythrocytes & reproduces
▫ Erythrocytes break open & release the parasite;
this causes the characteristic fever, chills, anemia,
weakness, hemorrhaging
▫ Intense fever & chills about 48 - 72 hr after
exposure, due to the simultaneous rupture of so
many erythrocytes
Malaria
• Transmission and Symptoms (cont.)
▫ The sexual stage of Plasmodium develops in the
human host and is picked up by a mosquito
▫ The sexual stage is completed in the salivary gland
of the mosquito to complete the cycle
▫ Treatment by quinine & other antimalarial drugs
Cryptosporidiosis
• Cause: Cryptosporidium species
▫ Alveolate apicomplexian
▫ A common protozoan parasite in humans
• Transmission and Symptoms
▫ Contaminated water
▫ Mild diarrhea in non-immunosuppressed persons
▫ Severe diarrhea in immunosuppressed persons