Fungi, Algae, Protozoa & Arthropod Vectors

Fungi

• 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 immitisDomain: 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 + arthroconidiaParasitic: 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

• 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

Prototheca wickerhamii

Chlorella species

Algae: rarely cause infectious disease

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 insidiosumDomain: 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 gondiiDomain: Eukarya

Kingdom: Protista

Apicomplexan

Etiologic agent of toxoplasmosis

Life cycle of Toxoplasma gondii

Definitive host

Int. hosts

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 rickettsiiDomain: Prokarya

Kingdom: Bacteria

Vector: ticks – Dermacentor andersoni, Dermacentor virabilis and Rhipocephalus sanguineous)

Disease: Rocky mountain spotted fever

3 host tick life cycle