Parasitology

what is the term for parasites that only infect humans?

what is the term for parasites that only infect humans?

Anthroponosis

what is the term for animal parasites that infect humans?

Zoonosis

What is the difference between a parasitic and a symbiotic relationship?

In parasitism, it is only the parasite that gains benefit, but symbyosis is beneficial for both.

What does ectoparasite and endoparasite mean?

ectoparasites are only in the surface but endo- are inside the body of the host.

What are the 4 types of parasitism?

1.Accidental

2.Optional

3.Obligatory (parasitic organism that cannot complete its life-cycle without exploiting a suitable host)

4.Erratic (wanders in to an organ in which it is not usually found)

What are the two main types of host?

1.Final host

2.Intermediate host

What is a reservoir?

A place such as an animal, soil, or human where the parasite is able to thrive for a long duration of time.

What is the difference between a monoxenic and heteroxenous life cycle?

Monoxenic=Evolution of parasite during the same host

Heteroxenic= when there is several hosts (e.g plasmodium)

Draw and describe the life cycle of Schistosomiasis:

1. cercariae penetrate the skin of a human that is usually in the aquatic environment like a lake.

2.The worm then loses its tail inside the host to become schistosomulae.

3. They then migrate to the liver where there is sexual reproduction of the parasite.

4.The eggs are then shed through the urine or feces and return back to the environment.

5.The eggs hatch and release the miracidia.

6.The miracidia then penetrate a snail, they then develop into free-swimming cercariae that are released from the snail.

7.The cercariae can now infect a human to start the life cycle again

Describe and draw the life cycle of Leishmaniasis:

This is a vector-borne transmission. A sandfly takes a blood meal from a human. Promastigotes enter the host through the blood circulation and are phagocytosed by macrophages. Then, the promastigotes transform into amastigotes inside the macrophage. The amastigotes multiply. A sandfly takes a blood meal and ingests the macrophages with the amastigotes inside. The amastigotes then become promastigotes again and live inside the sandfly. Next time, the sandly will take a blood meal, it will infect the human again to repeat the cycle.

Name strategies to control parasite infections:

1.Control of food and water

2.Control of intermediate hosts

3.Vector control

4.Vaccines

What are vectors?

A vector allows for the active transmission of parasites between humans and or other hosts. BUT snails are not vectors because they do not contribute actively to the transmission.

What type of animals are vectors?

Arthropods

Name 3 vectors of parasites:

1.Anopheles mosquito

2.Sandfly

3.Tse-tse files

What are the 5 types of vector control methods

1.Sanitizing method

2.Physical methods

3.Chemical methods

4.Ecological method

5.Biological method

Explain the sanitizing method for vector control

Use of traps for mosquitoes such as UV and CO2 traps.

Use of a biconical blue and black trap where the colours attract the vectors, and an attractive odour such as acetone is diffused.

Explain the physical method for vector control

The aim is to diminish the contact between the host and the vector. For example we can put mosquito nets around the bed or where long sleeves clothes to avoid the mosquito bites.

Explain the chemical method for vector control

Use of insecticides in the environment but also on the host, by using mosquito repellant for example

Explain the ecological method for vector control

This is related to making the environment of the vector more difficult for its survival. For example it can be to drain swamp areas, to reduce the areas where the mosquito can lay its eggs. This can also be the removal of aquatic plants against flukes as seen in lac d’annecy every year.

What does a Bio-rationale chemical method mean?

Insecticide that is based on the physiology of the vector but that is respectful of the environment.

Explain the biological method for vector control

Reducing populations of the vector by using living organisms or their products. For example, the use of some bacteria that produce toxins that lead to the death of the insect larva.

Give 2 examples of biological methods for vector control

1.The use of some bacteria (Bacillus thuringiensis) that produce toxins that lead to the death of the insect larva.

2.Introduction of sterile males into the enivronment via methods such as irradiation, genetic modifications etc.

Explain 2 main ways that invasive species have been introduced:

1.Intentional→ Pets and crops for medical or aesthetic reasons

2.Unintentional→Transport of goods where species survive to the transportation.

Briefly mention some of the consequences that invasive species can have on the ecosystem.

Some species that are introduced in either an intentional or unintentional way can contribute to the dissapearance of species of plants or animals. An example is the asiatic hornet (frelon asiatique) that has been introduced in a non intentional way and kills bees.

Name some antimalarial drug

Quinoline type (chloroquine, quinine); napthoquinone (atovaquone)

Explain the mechanism of action of quinolines

The drug accumulates in the parasite’s digestive vacuole and inhibits heme biominerilization leading to an accumulation of a cytotoxic complex.

Explain the mechanism of action of napthoquinone

Function as an antimetabolite, it is an analogue of coenzyme Q and inhibits oxidative phosporylation,

What does ACT stand for? what is it for?

Artemisin combination therapy used to treat malaria

what are the 2 drugs in ACT

Pipéraquine and Luméfantrine

Name 3 drugs active against malaria

1.Luméfantrine

2.Pipéraquine

3.atovaquone

Name the four things we can inhibit using antimalarial drugs

1.heme biomineralization

2.oxidative phosphorylation

3.trypanothione reductase

4.polyamine metabolism

Name a class of anti amobeic drugs

Nitro-5-imidazole

Name a drug from the Nitro-5-imidazole family

Metronidazole, tinidazole

Explain the mechanism of action of Nitro-5-imidazoles:

Nitro-5-imidazoles interact with pyruvate ferredoxine

oxydoreductase (PFOR) leading to the production of Reactive oxygen species (superoxide anion) leading to DNA fragmentation and inhibtion of nucleic acid synthesis.

Explain why nitro-5-imidazoles are not toxic to the host

The host cells have SuperOxide Dismutase which is used to convert the ROS into H2O2 which is less toxic, this is then converted by catalases. BUT, parasites dont have these enzymes so the ROS accumulate.

Name 2 antimonial drugs

1.Glucantime

2.Pentostam

Explain the MOA of antimonials

SbV can transform into SbIII inside the amastigote to inhibit trypanothione reductase. Inhibition leads to an impairment in glycosomal activity, which increases the cell’s suspceptibilty to oxidative stress.

Explain the resistance mechanism of pentavalent antimonials

One mechanism of resistance is the increase in levels of trypanothione reductase in the amastigote, as well as an efflux of SbIII by ABC transporters.

Explain the MOA of amphotericin B (Ambisome)

Amphotercin B binds to ergosterol in the parasite cell membrane, which leads to the formation of pores and leakage of K+ out of the cell, leading to cell death.

Name 2 trypanocidal drugs

1.Suramine

2.Nifurtimox

What is a combination therapy we can use for trypanosome

NECT: Nifurtimox- Eflornithine Combination Therapy

Explain the mechanism of toxicity of Amphotericin B for the host

Ergosterol is structurally very similar to cholesterol, which are found in the membrane of animals and humans. So the drug can sometimes to bind to cholesterol and cause leakage of ions.

Name 3 antihelminthic drugs

1.Benzimidazole

2.Avermectines

3.Pyrazino-isoquinoline

What is the target of Benzimidazoles

Inhibition of tubulin polymerization by fixation to beta-tubulin dimers

What is the target of Avermectines

Inhibition of the nerve impulse leading to paralysis of the parasite by mimicking GABA

What is the target of pyrazino-isoquinolone

Impairs membrane permeability and leads to increase in permeability to Ca2+, also leads to paralysis

What can you treat using pyrazino-isoquinolone?

Schistosoma

Give an example of a parasitoses provoked by protists

Amoebiasis

Give an example of a parasitoses provoked by nematodes

Ascaridosis

Give an example of a parasitoses provoked by cestodes

Hydatidosis

Name a parasite where the human is the intermediate host

Echinoccoccus granulosus (sheep)

Name a parasite where the human is the final host

Taenia

Draw and Describe the life cycle of Taenia

1.Humans ingest raw or undercooked infected meat

2.Scolex attach to intestine

3.Worm grows inside the intestine of the human

4.Eggs from the adult pass through the human into feces

5.Eggs are released into the environment

6.Cows and Pigs can ingest the eggs while grazing

7.Oncospheres hatch and go into the muscle of the animal

8.The oncospheres develop into cysticerci