Parasitic Nematodes

Question 1

What are parasitic nematodes also known as?

Answer 1

Helminthes

Question 2

What are drugs used against parasitic worms called (as a group)?

Answer 2

Anthemintics

Question 3

What are the groups of drugs that have been created to treat parasitic nematode infections in the 1960s?

Answer 3

Benzimidazoles (1960s)

Question 4

What is the general target for all current anthelmitics?

Answer 4

Mainly neuromuscular junction

Question 5

Example of an imidazothiazole

Answer 5

Levamisole

Question 6

Example of a macrocyclic lactone

Answer 6

Invermectin

Question 7

Example of a spiroindole

Answer 7

Paraherquamide

Question 8

What do benzimidazoles target?

Answer 8

inhibit cellular transport and energy metabolism -> impair locomotion and reproduction

Question 9

What do imidazothiazoles target?

Answer 9

nicotine receptor antagonists -> muscle paralysis

Question 10

What do macrocyclic lactones target?

Answer 10

ligand-gated ion channels -> paralysis of nematode pharyngeal and body wall muscle

Question 11

What do spiroindoles target?

Answer 11

competitive cholinergic antagonist -> cause paralysis

Question 12

Challenges to treatment of parasitic nematode infections

Answer 12

multiple life cycle stages
complex body plan 
protective cuticle
mutlicellular
abundant and high reproduction capacity
some stages metabolically inactive - resistant

Question 13

Challenges with drug treatment

Answer 13

Resistance
Reliance
Denser stock (livestock)
Movement of livestock

Question 14

Solutions to challenges with drug treatment

Answer 14

Ensure effective treatment 
Reduce reliance 
Combination drugs
Correct dose
Quarantine

Question 15

Parasite response to the immune response (host)

Answer 15

Suppress TH1 response (inflammatory)
Activate TH2 response (anti-inflammatory)
Also secrete other substances

Question 16

Genomic targets for future drug treatment

Answer 16

differential gene expression sites (between parasite and host)
disease-causing genes

Question 17

Three types of gastrointestinal worm with greatest impact on human health and fitness

Answer 17

Ascaris
Trichuris (whipworm)
Necator and Ancylostoma (hookworm)

Question 18

Two parasitic worms that have a big impact on farming of animals

Answer 18

Haemonchus

Trichinella

Question 19

How do Ascaris and Trichuris infect their hosts (human)?

Answer 19

eggs passed in faeces - contaminate -> ingested

Question 20

At which stage of their respective lifecycles are Ascaris and Trichuris infective to humans?

Answer 20

Eggs (embryogenesis in soil)

Question 21

How do hookworms (Necator and Ancylostoma) infect their hosts (human)?

Answer 21

L3 larvae penetrate skin on foot

-> bloodstream->lung-> oesophagus-> intestinal epithelium

Question 22

How can Ascaris, Trichuris (whipworm), Necator and Ancylostoma (hookworm) infections be diagnosed?

Answer 22

eggs in faeces

Question 23

How does Haemochus infect their hosts?

Answer 23

L3 larvae are ingested, on grass eaten

Question 24

What is the host of the parasitic worm Haemonchus?

Answer 24

sheep and goats

Question 25

What is the significance of the parasitic worm Haemonchus?

Answer 25

most abundant sheep parasite globally

Question 26

Why are parasitic worms so important to the farming of animals?

Answer 26

reduces productivity of cattle, sheep and goats

Question 27

Brief life cycle of whipworms (Trichuris) and Ascaris

Answer 27

faeces -> soil -> mouth -> small intestine -> ...

Question 28

Brief life cycle of Necator and Ancylostoma

Answer 28

faeces -> soil -> foot -> lungs -> oesophagus -> small intestine -> ...

Question 29

What is the significance of parasitic worm infections in terms of human health and fitness?

Answer 29

Disability adjusted life years | - may not kill, but disable = reduction in productivity

Question 30

Methods for control of Trichinella

Answer 30

Effective public veterinary health programme Farm management practices (rodent control + hygiene Mandatory meat inspection Public health information

Question 31

Brief life cycle of Haemonchus

Answer 31

direct life cycle (no vector) | faeces(eggs) -> soil (L1-L2) -> infect host (L3) -> abomasum (L3-adult)

Question 32

Risk factors for infection by Haemonchus

Answer 32

``` young - 1st grazing season old genetics environmental factors exposure levels (conc. of eggs on grass) ```

Question 33

Methods for control of Haemonchus

Answer 33

``` monitoring mixed grazing (young and mature) alternating stock (sheep/cattle) stocking density pasture composition - anthelmintic plants, e.g. chicory ```

Question 34

Why might trichinella be of particular concern in terms of pig meat consumption?

Answer 34

It is a zoonotic parasite.

Question 35

At which stage of its life cycle does trichinella infect?

Answer 35

L1 larvae (encysted larvae in striated muscle)

Question 36

Why is trichinella re-emerging?

Answer 36

wild reservoirs political upheaval - i.e. Eastern Europe in the 1990s changes in animal husbandry global trade EU trade (Eastern Europe has natural reservoirs)

Question 37

What are the hosts of trichenella?

Answer 37

humans pigs (domestic) other predatory/scavenging animals

Question 38

Brief life cycle of trichinella

Answer 38

meat -> mouth -> small intestine (larvae to adults) -> larvae in mucosa -> encysted larvae in striated muscle

Question 39

Point of diagnosis for trichinella

Answer 39

striated muscle

Question 40

What are the groups of drugs that have been created to treat parasitic nematode infections in the 1970s?

Answer 40

Imidazothiazoles

Question 41

What are the groups of drugs that have been created to treat parasitic nematode infections in the 1980s?

Answer 41

Macrocyclic lactones

Question 42

What are the groups of drugs that have been created to treat parasitic nematode infections in the 2000s?

Answer 42

Spiroindoles