Module 2: Parasites and the Significance of Disease

Metagenomics

• Study of genetic material recovered from a mixed community of organisms.

• Uses environmental DNA (eDNA)

• Can check prokaryotic and eukaryotic DNA.

Environmental DNA (eDNA)

• DNA that is left behind from shedding from organisms.

• DNA is left behind in their surroundings such as soil, water, or air.

To check prokaryotic DNA you use…

• 16 s RNA

To check eukaryotic DNA you use…

• 18 s RNA

Barcode Region

• Variable region, can scan to see what species the organism is.

What are the limits of using environmental DNA?

• Don’t have evidence of where the DNA came from.

Cyclospora cayetanesis

• Unicellular parasite that causes intestinal disease.

• Causes cyclosporiasis

• Coccidian (circular parasite)

• Sheds oocysts rather than cyst than ova.

Microbiome

• Grouping of microorganisms (bacteria, fungi, viruses, protist) that live in a specific environment - typically the human body.

What is the possible origin of parasitism?

• Parasitism originated from Archea.

• Phylogeny supports the idea.

Describe bacteria as parasites

• 30 major groups

• 8 prominent groups

• Ex. Borrelia (lyme disease), Ricketssia, Elrichiosis

Legionelle pneumophila

• Bacteria that causes legionarrie’ disease.

• Pathogenic

Spirochetes

• Prominent parasites can be free-living.

• Practices horizontal gene transfer (HGT)

  • Plasmids → one-way gene transfer between bacteria.

Can plants be infected by bacterial infections

Yes, plants can be infected by bacterial infections. As well, parasites. Corals as well can be infected by bacterium.

Bdellovibrio

• Bacterial parasitiod.

• Parasitizes other bacteria with boring mechanism.

• Can possible be used to control antibiotic resistant bacteria

Bacterial Colonization of Unicellular Eukaryotes

• Bacteria can colonize unicellular eukaryotic cells.

  • Ex. Paramecium

Example of Bacterial Colonization of Uni. Eukaryotes

• Bacteria can colonize paramecium.

• Holospora is a type of bacteria and can colonize paramecium.

• Lives inside of the nucleus of paramecium species.

• Candidatus caedibacter is another example of bacteria that can colonize inside of paramecium.

Eukaryotes & Parasites

• Very diverse group.

• Includes many types of parasites.

• Includes plants, animals, fungi, and algae.

• Protists and protozoa → informal terms no taxonomic value

SAR Supergroup

• Stramenophiles

• Alveolata

• Rhizaria

Stramenophiles

• Lineage of eukaryotic organisms

• Diatoms, golden brown algae, water molds, oomycetes.

Pythium

• A genus of parasitic Oomycetes (water fungus)

P. insidiosum

• Causes infection - pythiosis in humans and animals.

• Lives in stagnant, warm, freshwater.

Blastocytis hominis

• Unicellular eukaryote associated with the human GI tract.

• Many people carry the parasite without any signs or symptoms.

Dioecious/Gonochoristic

• Having separate male and female individual organisms or structures.

Monoecious/Hermaphrotic

• Individual has both male and female reproductive structures.

Biological Species Concept

• Defines species on their ability to interbreed and produce viable offspring.

• Difficult to apply this concept to organsism that rarely or do not undergo s. reproduction.

Explain how Giardia lamblia relates to the Biological Species Concept

• G. lamblia → no mating events, but genetic exchange may occur.

What are some examples of organisms that do not fit the Biological Species Concept

• Entamoeba, Trichonmonas, Leishmania, Trypanosomas.

Explain the lifecycle of G. lamblia

• Cyst: Hard; can survive in cold water for months.

• Small Intestine: Cysts excyst → trophozoites.

  • Trophozoites: attaches to the small bowel with sucking disk.

• Encystation: occurs when the parasite moves to the colon.

• Cyst: Most common stage; found in feces.

• Transmission: the cysts are infections when passed in the stool or shortly later.

Trypanosome

• Parasitic protozoa

• Undergoes asexual reproduction: binary fission.

• Possible s. reproduction in the insect vector (ex. tsetse fly)

Trypanosoma brucei Experiment

• Causes sleeping sickness

• Two trypanosome stocks were use

  • 1 red fluorescent marker 1 green fluoro.

• Fly fed on both markers

• Tsete fly → parasite → mice → isolated parasite

  • Some parasites were yellow: had red and green markers

  • Indication of genetic recombination/exchange

What is the most common phyla of parasites in the Costa Rican forest?

• Apicomplexa

• Apicomplexa includes Plasmodium (malaria), Cyclospora (cyclophorias), Toxoplasma (Toxoplasmosis).

• All but a few are parasitic

Are parasites gonochoristic?

• No, they have both make and female reproductive parts.

Dracunculus medinensis

• Parasitic roundworm/nematode.

• Known as Guinea Worm

• Worm incubates for a year inside of the body.

• Female worm emerges from the body (typically in lower extremities).

Life cycle of Dracunculus medinensis

• Larvae copepods are swallowed are swallowed from contaminated water.

• Larvae are freed from copepods in small intestine.

• Larvae penetrate from the small intestine and enters the abdominal wall.

• Larvae enters the subcutaneous tissue and matures there.

• Larvae travels to lower extremities.

• Blisters rupture releasing the larvae.

• Larvae infect copepods.

Transmission of Guinea Worm

• Transmission mostly occurs during dry seasons.

• Many people in Africa depend on rivers for water.

• Water during drought season becomes concentrated with the parasite.

Ovoviviparous

• Produces eggs that hatch inside that gives birth to live young.

• Inside the body

Viviparous

• Gives birth to live young, which the offspring develops inside the body from the mother’s nourishment.

Approaches to Guinea worm Prevention

• Filters: drinking water was filtered with specially made nets. They removed the copepods. Also drinking water through filter straws.

• Larvicide

• Health Education

• Providing clean water from wells.

Apicomplexa Characteristics

• Phylum is a part of the alveolate lineage.

  • some of the deadliest pathogens.

• Secretory organs

• Unicellular parasite protozoan

• Ex. Plasmodium (malaria) and Toxoplasma gondii (toxoplasmosis)

Apical complex

• Structural fibers and attachments that aid in the attachment and penetration into a host cell.

Apicoplast

• Plastid with essential metabolic functions inside of an ampicomplexa.

• Can hold DNA

• Bound by four membranes.

• Acquired by secondary endosymbiosis

Amblyomma americanum

• The Lonestar Tick

• Very abundant in the Southeastern US

• Can attack at any life stage.

• Transmits human monocytic ehrlichiosis and STARI

Dermacentor variabilis

• American dog tick

• Found throughout Georgia

• Vector of: RMSF, Tularemia, Ehrlichiosis, tick paralysis

Amblyomma maculatum

• Gulf Coast Tick

• Can transmit Rickettsia parkeri rickettsiosis, a form of spotted fever

Ixodes scapularis

• Black-legged tick

• Long mouth parts

• No festoons

• Common in North Georgia

• Known as the deer tick

• Can cause lyme disease, Ehrlichiosis, Babesiosis

Rhipicephalus sanguineus

• Brown dog tick

• Short mouthparts and festoons

• No white markings

• Common throughout Georgia; can reproduce indoors.

• Can cause RMSF, dog pathogens, and others

Oropouche Virus

• OROV and orthobunyaviruses

• Transmitted through arthropods (insects)

• Causes oropouche fever → can be fatal

Culicoides paraensis

• Not the same as mosquitoes or flies.

• #1 transmitters of the Oropouche virus.

• Found in hot and humid climates.

• First discovered in Trinidad and Tobago

OROV Concern in Georgia

• Oropouche virus cases are trending North. Global warming (hotter, more humid climates) = OROV can become a North American arbovirus.