Introduction to medically Important Parasites

Question 1

Parasitic disease where a vaccine is available:

Answer 1

Malaria, available for people in areas where malaria is endemic

Question 2

Which country has the highest incidence of the roundworm strongyloides?

Answer 2

Australia

Question 3

What are parasites?

Answer 3

Eukaryote pathogenic or commensal organisms

Question 4

What is the problem with eukaryotic parasite diseases?

Answer 4

They are very similar to human cells so drugs can be toxic to humans as well

Question 5

What are direct parasite life cycles?

Answer 5

Only one host in life cycle

Question 6

What are indirect parasite life cycles?

Answer 6

Two or more hosts required

Question 7

What are the types of parasite life cycles?

Answer 7

Direct

Indirect

They can undergo both sexual and asexual reproduction (usually in definitive host)

Question 8

What are the types of hosts that parasites can live in?

Answer 8

Definitive/primary host

Reservoir host

Secondary/intermediate host

Question 9

What are the modes of transmission of parasite infections?

Answer 9

Direct

Food/water borne

Via vector/intermediate host

Question 10

What happens in the intermediate host?

Answer 10

Can be just mechanical transmission or several important life-cycle stages can take place here.

Question 11

What is the efficacy of the RTS,S/AS01 (Mosquirix) vaccine?

Answer 11

26%

Question 12

What is leishmanisation?

Answer 12

Inoculating live parasites in the buttock to prevent leishmaniasis disease

Question 13

What are the types of disease causing parasites?

Answer 13

Single celled

Intracellular

Extracellular

Question 14

What type of evolution was required for pathogenic parasites to form?

Answer 14

Co-evolution

Question 15

What is the most common protozoan parasitic disease?

Answer 15

Trichomonas vaginalis (200 million cases detected worldwide)

Question 16

What kind of condition does Trichomonas vaginalis cause?

Answer 16

An STD

Question 17

What kind of pathogens are acanthamoeba and naegleria fowleri?

Answer 17

Protozoan parasites causing uncommon but deadly conditions.

Question 18

What is the disease caused by naegleria fowleri called?

Answer 18

Primary amoebic encephalitis

Question 19

What is the survival rate of naegleria fowleri infection?

Answer 19

No one has survived it (95% fatality even with treatment) Very rare with 340 cases recorded since the 1960s

Question 20

What common parasites are water borne?

Answer 20

Giardisis (relatively benign)

Toxoplasmosis (also benign and present in a huge percentage of the population)

Amoebiasis

Blantidiasis

Cryptosporidiosis

Question 21

What common parasites are caused by vector borne protozoan infections?

Answer 21

Malaria

Babesiosis

Leishmaniasis

Chagas disease caused by Trypanosoma cruzi

Sleeping sickness (trypanosoma brucei gambiensie/rhodesiense)

Question 22

What measures must be taken with systemic helminth infections and why?

Answer 22

To use immunosuppression due to the immunogenic nature of helminth infections. Helminths are also eukaryotes which means drugs are toxic

Question 23

How long do helminths stay in the body for?

Answer 23

They can survive for decades

Question 24

What are the types of helminth infections?

Answer 24

Nematodes (round worms)

Platyhelminths (flat worms) - Cestodes (tapeworms) and trematodes are the disease causing subgroups.

Question 25

Possible benefits to helminth infections:

Answer 25

Hygeine hypothysis. (infection with helminths at young age associated with protection from atopic illnesses like asthma and Irritable Bowl Disease)

Question 26

What is caenorhabditis elegans?

Answer 26

A nematode that is possibly one of the most important nematodes for medicine due to its use in research.

Question 27

How is caenorhabditis elegans used?

Answer 27

It is transparent and emits blue/green light.

Question 28

What is the second largest phylum in the animal kingdom?

Answer 28

Nematodes (25000 species discovered and 1 million predicted to exist)

Question 29

What parts of the body do helminths commonly cause infections in humans?

Answer 29

GI tract (eg hookworms) Tissue or blood (eg Filarial worms)

Question 30

What kind of nematode infections are most common?

Answer 30

GI infections

Question 31

How many people have GI nematode infections?

Answer 31

3.5 billion people (450 million seriously ill) 125000 deaths per year and 39 million DALYs

Question 32

Do GI tract infecting nematodes have intermediate hosts?

Answer 32

No they are direct parasites

Question 33

What is the most common cause of GI nematode infections?

Answer 33

Ascaris lumbricoides (~3000 deaths/yr)

Question 34

What GI nematodes cause infections in humans?

Answer 34

Ascaris lumbricoides Hookworms Trichuris trichura Strongyloides stercolis Enterobius vermicularis

Question 35

What kind of infection does enterobius vermicularis cause in humans?

Answer 35

Commonly infects children globally and causes itch on buttocks

Question 36

Which worm is expected to be eradicated next?

Answer 36

A tissue infecting nematode worm called guinea worm (Dracunulus medinesis) in 1986 there were 3.6 million cases and in 2015 only 22 cases

Question 37

What are the filarial worms that cause infection in people?

Answer 37

Lymphatic filiariasis Trichinella spiralis (only intracellular helminth)

Question 38

What are the types of tissue infecting nematodes?

Answer 38

Filarial worms such as lmyphatic filiariasis and trichinella spiralis Guinea worm Toxocara canis

Question 39

What kind of infection does toxocara canis cause?

Answer 39

Worm often targets the eye

Question 40

How do tapeworms attach to the gut?

Answer 40

Via scolex

Question 41

What mode of reproduction do tapeworms use?

Answer 41

They are hermaphrodites and reproduce by sexual reproduction

Question 42

What are tapeworm bodies composed of?

Answer 42

Segments or proglottids

Question 43

What does the tissue tapeworm echinococcus multilocularis do?

Answer 43

It is a parasitic infection that acts very similarly to cancer

Question 44

What common Intestinal tapeworm is obtained from consuming pork?

Answer 44

Taenia solium

Question 45

What are the types of tapeworms?

Answer 45

Tissue and intestinal. Intestinal tapeworms can also form cysts in tissues

Question 46

What common Intestinal tapeworm is obtained from consuming beef?

Answer 46

Taenia saginata

Question 47

Are flukes also haemaphrodites?

Answer 47

Yes with the exception of schistosomes which are dioecious

Question 48

What are the types of blood flukes?

Answer 48

Schistosoma mansoni (gut) Schistosoma haematobium (bladder) Schistosoma japonica (gut) These organisms can produce growth factors which is why some cancers can arise from these parasites (eg bladder cancer from schistosoma infection)

Question 49

What are the types of tissue flukes?

Answer 49

Most infect liver and lungs. Fasciola hepatica Clonorchis (opisthorchis) sinensis Opisthorcus viverrini Paragonimus westermani

Question 50

Why are helminth treatments so underdeveloped?

Answer 50

The diseases are more prevalent in the tropics and so drug companies cannot make profit making drugs for these diseases. Helminths are eukaryotic so drugs are often toxic

Question 51

What treatment is used for sleeping sickness?

Answer 51

Malarsoprol which is deadly in 8% of patients and contains 'arsenic dissolved in antifreeze' (this drug is used for stage 2 of the disease) Eflornithine treats 1 of the 2 causes of the disease rater harmlessly.

Question 52

What drugs are used for chagas disease?

Answer 52

Only 2 drugs available to treat chagas, in the 1990s Bayer decided that one of them was not profitable and withdrew it from production (Niturtimox) The drugs only work in the first 2 - 4 weeks

Question 53

What drug is used to treat leishmaniasis?

Answer 53

Pentavalent animony first used in 1930s and is the first choice drug for most cases