L5: Complex Pathogen Life Cycles Flashcards
3 main types of leishmaniasis?
- Visceral
- Cutaneous
- Mucocutaneous
Example drug commonly used to treat VL?
Antimonials.
Sudanese epidemic occurred between?
1985 - 1987.
Leishmaniasis life cycle.
- Bite of female sandfly. Promastigotes enter bloodstream.
- Promastigotes taken up by phagocytes. Form amastigotes.
- Multiply and infect other phagocytes.
- Phagocytes taken up by sandfly in a bloodmeal.
- Migrate to the gut and reform promastigotes.
CYCLE REPEATS.
Give some reasons as to why we think we can make a vaccine for leishmaniasis.
- Single life cycle stage responsible for infection - amastigotes.
- No antigenic variation.
- Sub clinical infection is common.
T. cruzi causes what disease?
Chagas disease.
T. cruzi life cycle.
- Kissing bug takes a blood meal –> deposits faeces near wound. Trypomastigotes infect local tissues and differentiate into amastigotes.
- Differentiate into trypomastigotes –> burst cell and enter bloodstream.
- Invade other tissues. Can only replicate once they’ve entered another cell and differentiated into intracellular amastigotes.
- Bug reinfected when taking bloodmeal.
Obstacles in forming trypanosome vaccines?
- 2 life cycles responsible for the disease.
- Antigenic variation.
- Brucei = crosses blood brain barrier.
- Cruzi = many challenges, e.g. genetic diversity, infects all nucleated cells, has many animal reservoirs.
What is amoebiasis?
Disease caused by several protozoan species of the genus Entamoeba, e.g. Entamoeba histolytica.
Giardiasis is a disease caused by the gut microbe…
Giardia lamblia.
Three main types of helminths (parasitic worms)?
Tapeworms, flukes and roundworms.
Two common types of tapeworm?
Taenia saginota and T. solium.
Tapeworm life cycle?
- Eggs of proglottids found in faeces.
- Cows/pigs ingest faeces. Larval form hatch and cysts form in muscles.
- Humans ingest uncooked/raw meat.
- Adult tapeworm latches onto the wall of the s.intestine using its scolex.
- Produce proglottids –> pass into faeces.
Explain the life cycle of Schistosomiasis.
- Eggs eliminated within faeces.
- Hatch and form miracidia, penetrate snail host.
- Form cercariae, which are released and penetrate the skin of the human host.
- Shed forked tail, form schistosomulae. Reside in veins.
- Mature into adult worms which lay eggs; released into the faeces.
What type of helminth is Ascaris lumbricoides?
Roundworm.
Explain the life cycle of Ascariasis.
- Adult roundworm found in the small intestine. Eggs released into faeces.
- Depending on environmental conditions, eggs become infective.
- Swallowed –> larvae hatch –> intestinal mucosa –> enter the system circulation of the lungs.
- Re-enter the s. intestine.
- Develop into adult worms.
Advantages of inactivated vaccines?
- They pose no risk of contracting the disease.
2. Safe in immunodeficient patients.
Advantages of attenuated vaccines?
- Community immunisation (indirect).
- Lifelong immunity.
- Booster vaccinations not required.
Disadvantages of inactivated vaccines?
- Require booster vaccinations.
2. Administration = injection.
Disadvantages of attenuated vaccines?
- Increased chances of vaccine-induced disease.
2. Unsafe for immunodeficient patients.
Basic life cycle of Plasmodium falciparum?
- Enter the hepatocytes of the liver as sporozoites (exo erythrocytic stage).
- Merezoites then infect the RBCs.
Plasmodium falciparum shows growing resistance towards two commonly used drugs for malaria. Name these.
Quinolines and anti-folates.
Artemisinin compounds used to treat malaria. Benefits?
- Rapid response.
- Works against drug resistant P. falciparum.
- Well tolerated by patients.
- Reduced gametocyte carriage.
