Selected Fungal and Protozoan DiseasesUpdated Summer 2015Jerald 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. CandidiasisB. DermatophytosisC. CryptococcosisD. HistoplasmosisE. BlastomycosisF. 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. Amebiasis B. Primary Amebic Meningoencephalitis C. Giardiasis D. Trichomoniasis E. Balantidiasis F. Toxoplasmosis G. Malaria H. 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