Parasitology Flashcards
What is a vector?
An organism that transmits a disease or parasite from one host to another.
protozoa infection
Single-celled organisms that can cause diseases
Transmitted by insects
Who cause and transmit Malaria?
Plasmodium
mosquitoes transmit plasmodium to human
What factors contribute to the prevalence of malaria?
Poverty and climate conditions that favor mosquito populations.
What is the life cycle of Plasmodium?
- Mosquito injects sporozoites into the blood vessels (~100 cells)
- Sporozoites travel to the liver, stop there for a week (varies depending on species), replicate to 1000 cells
- Become Merozoites
- Merozoites invade red blood cells
- Replicate in RBCs asexually can form a ring structure in RBC (key diagnosis feature under microscope)
This cause problem, the infected RBCs become sticky and stick to blood vessel block the blood, leading to starve for oxygen, brain will stop functioning finally
- Some Merozoites can convert to Gametocytes which will transmit to mosquito and start another cycle
What happens to infected red blood cells (RBCs) in malaria?
Infected RBCs become sticky, adhere to blood vessels, and can block blood flow.
True or False: There are vaccines available for malaria.
False
What are gametocytes in the context of malaria?
Forms of the parasite that can be transmitted back to mosquitoes.
What is the role of mosquitoes in the transmission of malaria?
Mosquitoes inject sporozoites into humans and can receive gametocytes from infected individuals.
What is the difference between parasites and bacteria
Parasites are larger in size, and have more complex cellular structures
Parasites are eukaryotes with nucleus and other complex structures.
They can be single cell or multicellular
There is no vaccines for disease caused by parasites
Bacteria are sigle cellular prokaryotes
Have vaccines for many diseases
Discovery of malaria
Charles Laveran: find malaria is caused by parasites in blood (see parasites in blood)
Ronald Ross: find malaria is transmit by mosquitoes (see parasites in mosquitoes)
Tu youyou: find treatment (Artemistin 青霉素)
What is the name of the Africa sleeping sickness?
African Trypanosomiasis
The cause parasite and the vector of African Trypanosomaisis
Caused by Trypanosome Brucei
Transmitted by Tsetse fly
The geography of African Trypanosomaisis
Only present in Africa
Where did parasites go after got African Trypanosomaisis
Parasites go into the central nerve and then go into the brain, cause confusion and a “coma” state (looks like sleeping), finally become severe encephalitis which lead to death.
Trypanosome Brucei Life Cycle
- Tsetse fly injection to human, Trypanosome Brucei go into bloodstream
- T. Brucei multiplies by binary diffusion in blood, lymph, and spinal fluid, T. Brucei is relatively large, it will let the organ be overwhelmed with the parasites
- Another Tsetse fly ingest T. Bruce
- T. Bruce multiplies in their midgut by binary diffusion
- T. Bruce transform to a infectious stage and enters the salivary gland and multiplies, wait to go into another host
How long & where does Trypanosomes existes? What is their host at that time?
200 million years
Africa and South America
Dinosaurs
Which type of Trypanosome is found in Africa and South America?
Africa: T. Brucei
South America: T. Curzi
What is the difference between T. Brucei and T. Cruzi
- T. Cruzi has much larger mitochondria
- Their vectors are different, T. Brucei transmit by testes fly, T.cruzi transmit by bettle called Triatomine or assassin bug
- T. Brucei infect the blood stream but the T. Cruzi infect muscle
T. Cruzi’s life cycle
- Traitomine bite on human at night
- .T.Cruzi go into human heart muscle, colon muscle, and esophagus muscle
- It transform to amastigote, replicated in the muscle cells
- Muscle cells finally burst open
- Amastigote transform to trypomastigote
- When there is another bite, the trypomastigote will go back to the Traitomine and multiplied in them
What disease does T. Cruzi cause?
It causes Chagas disease
Once you got infected, you will carry it for the whole life and the parasite inside the muscle cell will weaken you heart and cause heart attack, most of the people die from heart attack, but it you can live longer, it will cause problems in your intestine.
How did this disease become worldwide?
Due to the long symptomatic time, people who carrier those parasites they don’t know they were infected and they travel around world spread the parasites all over the world
What cause and what transmit Leishmaniasis?
Caused by leishmania
Transmitted by sandfly
What are two forms of Leishmaniasis? And their related symptom, parasites, and treatments?
1.Visceral Leishmaniasis
-cause enlargement of organ
-will die if not treated
-caused by L. Donovanii
-have very good and effective treatment: Ambizome
2.Cutaneous Leishmaniasis
-stay in the skin
-not deadly, usually self-healing
-caused by L. Major
No good treatment
What is the problem of the geography of Leishmaniasis?
Some countries are labeled to have this disease but actually there is only few regions in the country have the disease (ex. .Brazil and India)
How large is the sandfly?
Half size of mosquito
Leishmania Life cycle
- Sandfly feed on human transfer the promastigote to human body
- Promastigote has flagella, it infect the macrophage s in liver
- Macrophage engulf them, they transform to amastigote, replicate in macrophage and finally burst it open
- Amastigote convertie back to promastigote wait for next sandfly
What is the principle of the drug abizome? What is the advantage of this drug?
It go into macrophage, set on tope of the amastigote, melt its membrane
This happens so fast (treat in the afternoon, cure at night), the cell don’t have time to develop there resistance
What molecule does amastigote has on its surface? Human?
Amastigote: ergosterol
Human: cholesterol
Post kalaazar dermal leishmaniasis (PKDL)
10-25% of people who got treatment for Visceral infection has these white patches contain the parasites on their skin, unable to confirm PKLD as major reservoir for transmission
What are the disadvantages of field study?
The sample size sometimes are small
And you can’t repeat your study
Usually parasites have two stages: i and d
I: infective stage (in vector)
D: diagnostic stage (in human)
Helminth infection transmitted type
- Soil transmitted
Ascaris
Trichuris
Hookworm - Insect transmitted
Lymphatic Filariasis
Onchocerciasis - Snail transmitted
Schistosomiasis
Morphology of 3 major STHs
- Ascaris
20 cm, 1 year, 20,000 eggs/day - Trichuris
5 cm, 2 years, 5000 eggs/day - Hookworm
15 mm, 5 years, 10,000 eggs/day
Transmitted method and living space of the 3 STHs
- Ascaris and Trichuris
ingesting eggs - Hookworm
Larvae
All their adult worms live in intestine (gastrointestinal tract), the adult didn’t replicate in the intestine, but they mate and produce eggs and transmit through feces
Human are their only host
Major symptoms of STHs
Children growth: Malnutrition, growth stunting, cognitive and learning defects
Many suppress immune response to other infections
Ascaris life cycle
- Human ingest eggs
- Eggs grow to larvae, the larvae go through the big and small intestine and then go to the lung
- Finally go back to the digestive system stay in small intestine
Hookworm life cycle
- Larvae infect people through skin
- Go through lung and finally stay in intestine
- Adults mate in the small intestine, produce eggs that released to the environment by feces
- Grow to rhabditiform larvae
- Grow to filariform larvae (can infect people through skin)
Diagnosis of STH infection
The intensity of infection is measured by the number of eggs/g of feces
Determine under microscope
Treatment of STH infection
Goal: remove all the adults from the intestine
Common drugs: benzimidazoles and Ivermectin
Principle: paralyze the adult parasite
Problem: does not kill eggs
elephantiasis: disease name, caused by, transmitted by?
Lymphatic filariasis
Caused by Wuchereria Bancroft
Transmitted by mosquito
Wuchereria Bancroft life cycle
- Mosquito transmit larvae (L3) to human
- Adult worm in lymphatic block flow of lymphatic fluid, cause accumulation of lympatic fluid
- Adult worms produce Microfilaria that migrate to lymph and blood canals
- Microfilaria can be taken by mosquitoes and they develop to L1 larvae in mosquito and grow to L3 larvae
Riverblindness: disease name? Caused by? Transmitted by? What cause blind?
Onchocerciasis
Caused by Onchocorca Volvulus
Transmitted by blackflies
Microfilaria accumulate in the eye causing blindness
Hypothesis about helminth infection and autoimmune disease
It is hypothesized that helminth infection can reduce auto-immune disease, the infection might suppress the immune system, reduce the overall inflammation associated with autoimmune disease.
