Fungi, Algae, Protozoa &
Arthropod Vectors
Fungi
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Ubiquitous!
Have a cell wall = chitin
Are eukaryotes
Have a true nucleus
Reproduce sexually + asexually
Most don’t cause disease
Disease can be direct (infection) or indirect
(ingestion of toxin produced by the fungus)
Coccidiodes immitis
Domain: Eukarya
Kingdom: Fungi
Etiologic agent of coccidioidomycosis (“Valley
fever”)
Narrow environmental range: semi-arid zones of SW
US, Mexico, Central & South America
Dimorphic fungus:
Saprophytic: environmental temp - filamentous
fungus (mold) with branching septate hyphae +
arthroconidia
Parasitic: body temp: yeast form – large fungal
spherules + division (endosporulation) to produce
endospores
Arthroconidia → spores → inhalation by mammals
→ spherules → endospores
“Imperfect fungus” – no known sexual stage
Algae
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Aquatic or semi-aquatic environments
Have a cell wall (cellulose)
Are eukaryotes
Have a true nucleus
Photosynthetic (chloroplasts)
Reproduce sexually + asexually
Disease most often = indirect (toxic algae)
Algae: Cyanobacteria
Most common causes of toxic blooms:
Anabaena, Aphanizomenon, and Microcystis species
Hepatotoxic: cause
acute submassive to
massive
hepatocellular
necrosis → liver
failure
Algae:
rarely cause infectious disease
Chlorella species
Prototheca wickerhamii
Slime molds and water molds
• Slime molds: ameboid cells
– Phagocytic
– Cellular slime molds: single cells, can aggregate to
form a “slug” → fruiting body + spores →
dissemination
– Plasmodial slime molds = multinucleated; diploid cells;
also spread by fruiting body/spores
• Water molds = oomycetes
– Cell wall = cellulose
– Flagellated
Pythium insidiosum
Domain: Eukarya
Kingdom: Protista
Oomycete (Water mold)
Etiologic agent of pythiosis
(“Kunkers”)
Warm, wet environments
Pythium insidiosum
Protozoa
• Eukaryotes that don’t fit into any of our other
categories
• True nucleus
• No cell wall, no chloroplasts
• Reproduce sexually + asexually
• Most don’t cause disease
• Disease causing protozoa can be free
living/opportunists or obligate intracellular
parasites with a complex life cycle
Toxoplasma gondii
Domain: Eukarya
Kingdom: Protista
Apicomplexan
Etiologic agent of
toxoplasmosis
Life cycle of
Toxoplasma gondii
Int. hosts
Definitive
host
Vector transmitted diseases
• vec·tor (vktr)n.1. Mathematicsa. A quantity, such as
velocity, completely specified by a magnitude and a
direction.
• b. A one-dimensional array.
• c. An element of a vector space.
• 2. Pathology An organism, such as a mosquito or tick, that
carries disease-causing microorganisms from one host to
another.
• 3. Genetics A bacteriophage, plasmid, or other agent that
transfers genetic material from one cell to another.
• 4. A force or influence.
• 5. A course or direction, as of an airplane.
Vector transmitted diseases
• Mechanical vectors
• Biological vectors
• Arboviruses
Plasmodium species
Domain: Eukarya
Kingdom: Protista
Etiologic agent of malaria – 5
species involved = P. vivax, P.
falciparum, P. malariae, P ovale
and P. knowlesi
Vector = Anopheles species
mosquitos
Life cycle of Plasmodium sp.
Rickettsia rickettsii
Domain: Prokarya
Kingdom: Bacteria
Vector: ticks – Dermacentor
andersoni, Dermacentor
virabilis and Rhipocephalus
sanguineous)
Disease: Rocky mountain
spotted fever
3 host tick life cycle