L5: Complex Pathogen Life Cycles

Question 1

3 main types of leishmaniasis?

Answer 1

1. Visceral
2. Cutaneous
3. Mucocutaneous

Question 2

Example drug commonly used to treat VL?

Answer 2

Antimonials.

Question 3

Sudanese epidemic occurred between?

Answer 3

1985 - 1987.

Question 4

Leishmaniasis life cycle.

Answer 4

1. Bite of female sandfly. Promastigotes enter bloodstream.
2. Promastigotes taken up by phagocytes. Form amastigotes.
3. Multiply and infect other phagocytes.
4. Phagocytes taken up by sandfly in a bloodmeal.
5. Migrate to the gut and reform promastigotes.

CYCLE REPEATS.

Question 5

Give some reasons as to why we think we can make a vaccine for leishmaniasis.

Answer 5

1. Single life cycle stage responsible for infection - amastigotes.
2. No antigenic variation.
3. Sub clinical infection is common.

Question 6

T. cruzi causes what disease?

Answer 6

Chagas disease.

Question 7

T. cruzi life cycle.

Answer 7

1. Kissing bug takes a blood meal –> deposits faeces near wound. Trypomastigotes infect local tissues and differentiate into amastigotes.
2. Differentiate into trypomastigotes –> burst cell and enter bloodstream.
3. Invade other tissues. Can only replicate once they’ve entered another cell and differentiated into intracellular amastigotes.
4. Bug reinfected when taking bloodmeal.

Question 8

Obstacles in forming trypanosome vaccines?

Answer 8

1. 2 life cycles responsible for the disease.
2. Antigenic variation.
3. Brucei = crosses blood brain barrier.
4. Cruzi = many challenges, e.g. genetic diversity, infects all nucleated cells, has many animal reservoirs.

Question 9

What is amoebiasis?

Answer 9

Disease caused by several protozoan species of the genus Entamoeba, e.g. Entamoeba histolytica.

Question 10

Giardiasis is a disease caused by the gut microbe…

Answer 10

Giardia lamblia.

Question 11

Three main types of helminths (parasitic worms)?

Answer 11

Tapeworms, flukes and roundworms.

Question 12

Two common types of tapeworm?

Answer 12

Taenia saginota and T. solium.

Question 13

Tapeworm life cycle?

Answer 13

1. Eggs of proglottids found in faeces.
2. Cows/pigs ingest faeces. Larval form hatch and cysts form in muscles.
3. Humans ingest uncooked/raw meat.
4. Adult tapeworm latches onto the wall of the s.intestine using its scolex.
5. Produce proglottids –> pass into faeces.

Question 14

Explain the life cycle of Schistosomiasis.

Answer 14

1. Eggs eliminated within faeces.
2. Hatch and form miracidia, penetrate snail host.
3. Form cercariae, which are released and penetrate the skin of the human host.
4. Shed forked tail, form schistosomulae. Reside in veins.
5. Mature into adult worms which lay eggs; released into the faeces.

Question 15

What type of helminth is Ascaris lumbricoides?

Answer 15

Roundworm.

Question 16

Explain the life cycle of Ascariasis.

Answer 16

1. Adult roundworm found in the small intestine. Eggs released into faeces.
2. Depending on environmental conditions, eggs become infective.
3. Swallowed –> larvae hatch –> intestinal mucosa –> enter the system circulation of the lungs.
4. Re-enter the s. intestine.
5. Develop into adult worms.

Question 17

Advantages of inactivated vaccines?

Answer 17

1. They pose no risk of contracting the disease.

2. Safe in immunodeficient patients.

Question 18

Advantages of attenuated vaccines?

Answer 18

1. Community immunisation (indirect).
2. Lifelong immunity.
3. Booster vaccinations not required.

Question 19

Disadvantages of inactivated vaccines?

Answer 19

1. Require booster vaccinations.

2. Administration = injection.

Question 20

Disadvantages of attenuated vaccines?

Answer 20

1. Increased chances of vaccine-induced disease.

2. Unsafe for immunodeficient patients.

Question 21

Basic life cycle of Plasmodium falciparum?

Answer 21

1. Enter the hepatocytes of the liver as sporozoites (exo erythrocytic stage).
2. Merezoites then infect the RBCs.

Question 22

Plasmodium falciparum shows growing resistance towards two commonly used drugs for malaria. Name these.

Answer 22

Quinolines and anti-folates.

Question 23

Artemisinin compounds used to treat malaria. Benefits?

Answer 23

1. Rapid response.
2. Works against drug resistant P. falciparum.
3. Well tolerated by patients.
4. Reduced gametocyte carriage.