Module 1: Intro to Parasitology

Vector

• Carriers of parasites.

• Viruses, bacteria, protozoa

• Ex. Ticks, Nematodes, Kissing Bugs

Can vectors be carriers of parasites?

Yes

Neglected Tropical Disease

• Disease mostly in 3rd world countries.

• Not many resources for research and treatment.

Parasitology

The scientific study of parasites and their relationship (symbiosis) with a host.

Phoresis

• Attaches to another (host) and may take resources.

• Ex. Water mites, leeches

Symbiosis

• Two or more organisms are interacting.

  • Commensalism, mutualism, paratism.

Mutalism

• Both species benefit in the interaction.

• Potential used for coevolution.

• Ex. Bull horn acacia and ant.

Explain the mutualistic relationship between the Bull horn acacia and ant.

• The bull horn acacia provides habitat and food for the ant.

  • The ant protects the plant from predators through biting or stinging.

Commensalism

• One species benefits and one does not (no harm/help).

  • Ex. Spanish moss and tree.

Explain the commensal relationship between Spanish moss and the tree?

• The spanish moss is able to gain sunlight and support.

  • Tree is not harmed.

Parasitism

• Only one benefits in the relationship at the expense of the host.

• Ex. tapeworm (Taenia) and human.

• Encompasses: plants, insects, helminths, fungi, bacteria, protozoa.

Ectoparasite

• Parasite that attaches outside the host.

• Is specially adapted to attach to the host.

• Ex. Tick

Endoparasite

• Parasite that lives inside of the host.

• Have extreme specialization

Parasitoid

• Insect that lays eggs on the living host.

• Ex. parasitic wasp.

Host

• Living organism that harbors a parasite.

Definitive Host

• A parasite that is able to mature and reproduce.

Intermediate Host

• Parasite is not able to mature and reproduce within the host.

• Parasite undergoes required developmental change - can reproduce asexually.

• Ex. Fasciola hepatica (helminth).

Reservoir Host

• An organism that is harbors a parasite/pathogen, without getting sick.

Describe the stages of metamorphism.

Egg → Larvae → Pupae → Adult (circle)

Infectious Agent

• An organism that or sub organismal entity (virus) that is capable of producing an infection.

Infection

• Entry and development or multiplication of an infectious disease.

Pathogen

• An infectious agent that is capable of causing a state of disease.

• Produces a pathological condition.

Virulence

• When a parasite affects the host fitness.

Fitness

• The ability of pass on genes to future generations.

One Health

• Collaborative approach at various levels to understand the relationship between humans, animals, plants, abiotic factors in the environment.

• Global, local, and national scales.

• Transdisiplinary

Demodex canis

• Mites

• Cigar-shaped mite that lives inside dog hair follicles.

Wuchereia bancrofti

• Parasitic roundworm that causes filariasis (elephantiasis)

• Mosquitoes inject infectious larvae into human skin.

• Larvae grow into adult like worms and attacks the lymphatic system.

• Nematode

Are all copepods parasites?

No, but most are.

Helminths

• Large parasitic worms.

• Flat worms

Cestodes

Tapeworms

Nematodes

Roundworms

Trematodes

Flukes

Intracellular Parasites

• Parasites that live within the cell.

Extracellular Parasite

• A parasite that lives outside of the cell

Autogenic

• A parasite that is able to complete its entire lifecycle.

Allogenic

• A parasite that transforms (matures) through different ecosystems.

Epicellular

• A parasite that lives on the surface without going into the cell.

Obligatory Parasite

• A parasite that needs a host to survive.

• Depends on the host metabolically or physiologically.

• Ex. Malaria needs the mosquito to go onto it’s next stage.

Facultative Parasite

• A parasite that can complete its life cycle by itself, can act as a parasite when the opportunity arises.

Opportunistic Parasite

• Takes advantage of particular experiences to infect a host in a way that it foes not usually does.

Systematics

• The study of biological diversity and classification.

Taxa

Groups ranging from subspecies and species to genera, families, orders, class, phyla, and kingdom.

Taxonomy Order

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Microparasites

• Microscopic parasite species that multiply within the host.

• Ex. Rickettsia (bacteria) or Plasmodium (malaria)

Plasmodium

• Genus of protozoan parasites that causes malaria.

• Mosquitoes are vectors for this disease.

• Obligates

• Invades RBC’s, multiply, burst RBC’s causing sickness.

Macroparasites

• Larger, multicellular parasites that can live inside the host.

• No multiplication: usually release eggs for infection.

• Visible to the naked eye.

• Ex. Tapeworms and Ticks

Explain how the host is the “environment” for a parasite.

• The host is the environment where the parasite lives in.

• The parasite must adapt or become extinct as changes occur.

Parasites Ecological Niche

• Very complex

• Includes the resources needed for the parasites survival and reproduction.

Tunga penetrans

• Flea

• Burrows into the skin of humans and animals and causes skin infection.

Schistosoma mansoni

• Fluke/trematode

• Causes intestinal schistosomiasis in humans

• Snail (Biomphalaria) release larvae → larvae penetrate immature worms in humans → worms mature in humans (definitive host).

Snail Role in Schistosomiasis in humans

• They are an intermediate host.

• They release their larvae into freshwater.

Parathentic Host

• Transport host.

• Parasite does not undergo necessary development.

• Enables parasite to bridge a trophic gap.

Hyperparasite

• Parasite of a parasite.

Explain the hyperparasite relationship between dogs and tapeworm.

• The dog flea (tenocephalides canis) is an ectoparasite of dogs and people.

• Flea ingests parasite (diphylidium canimum) - a hyperparasite.

• Dog injests flea.

• Tapeworm develops in a dog.

Theileria

• Protozoan that infects RBC’s and WBC’s.

Asian Long Horned Tick.

• Haemaphysalis longicornis

• Native to China, Japan, and Korea

• Reproduction through pathogenesis → female produces her own offspring.

• Causes disease in cattle → carries theileria

Mechanical Vector

• Vector picks up the parasite from the host and transfers it to another, parasite undergoes no development.

• Ex. Horsefly and Trypsnoasoma evansi

Biological Vector

• Parasite develops in host transmitting disease.

• Ex. Tick and Borrelia → Lyme disease

What group do parasites mostly come from?

Protosomes. All protosomes belong either to lophotrochoza or ecdysoza.

Phylum Platyhelminths

• Flatworms

What are the characteristics of platyhelminths?

• Ciliated

• Soft body

• Incomplete digestive system

• Simple nervous system

• Male and female reproductive organs

• Eyespot

  • Found everywhere

Trematoda

• Flukes

• Anchoring and hooks

• May have 2 or more host.

Schistosoma

• AKA blood flukes

• Type of flatworm

• Fertilized egg breaks through intestinal wall → leaves through bladder.

• Causes schistosomiasis

Tapeworms

• Has male and female reproductive organs

• Can be long because of continuous growth.

• No eyes

• Ex. beef tapeworm (taenia saginata) from uncooked beef.

Proglottis

• Continuous growth

Phylum Nematoda

• Abundant and diverse

• Found everywhere

Characteristics of Phylum Nematoda

• Bilateral and symmetrical

• Developed digestion

• Cuticle molten as growth occurs

• Anus

Stylets

• Piercing organs in nematodes

Pharynx

• Aids in the sucking motion of nematodes.

How do nematodes reproduce?

• Sexual dimorphism: smaller hooks on males.

• Internal fertilization

• Development is indirect: egg → larva → adult

Lifestyle of Nematodes

• Active hunters of protist and small animals

• Can be parasitic to plants and larger animals.

• Approx. 50 species cause disease.

Hookworms

• Type of nematode that causes anemia.

• Comes from contaminated soil.

Trichinella

• Nematode that causes trichinosis.

• Comes from uncooked meat.

• Cyst on muscles.

Enterobius vernicularis

• Pinworms

• Causes anus itching

Ascaris lumbricoides

• Intestinal roundworms

• Can be long (~30 cm in females)