Parasites

Question 1

Platyhelminths examples

Answer 1

Cestodes (tapeworms)

Trematodes (flukes)

Question 2

Main parasites for human health

Answer 2

Trichuris (whipworm)
Ascaris
Necator & Ancylostoma (hookworms)
Lymphatic filariasis (Brugia)
Onchocerciasis (river blindness)
Dracunculus (guinea-worm)

Question 3

Most abundant sheep parasite

Answer 3

Haemonchus spp.

Question 4

Anthelmintic Drugs

Answer 4

Benzimidazoles (b-tubulin – locomotion & reproduction)

Imidazothiazoles (nicotinic receptor agonist – muscle paralysis)

Macrocyclic lactones (glutamate-gated chloride channels – paralysis)

Spiroindoles (cholinergic antagonist – paralysis)

Question 5

Target of Benzimidazoles

Answer 5

b-tubulin – locomotion & reproduction

Question 6

Target of Imidazothiazoles

Answer 6

nicotinic receptor agonist – muscle paralysis

Question 7

Target of Macrocylic Lactones

Answer 7

glutamate-gated chloride channels – paralysis

Question 8

Target of Spiroindoles

Answer 8

cholinergic antagonist – paralysis

Question 9

Life Cycle of Whipworm

Answer 9

Eggs infective, straight to digestive tract

Eggs passed in the faeces
Embryogenesis occurs in the soil & the eggs become infective (days)
Larval development to adult stages occurs in host
Live in the colon – fixed into the mucosa

Females deposit eggs at ~60 dpi
Life span of 1 year

Question 10

Life Cycle of Ascaris lumbricoides

Answer 10

Eggs infective, intestine-blood-lungs-small intestine

Eggs passed in the faeces
Embryonate the soil – infective eggs at ~18 days
Ingested eggs hatch in intestine
Larvae move to lings via blood
Develop further then move to throat and swallowed
Adults mature in small intestine

Female deposit eggs (2-3 months pi)
Life span of 1-2 years

Question 11

Life Cycle of Hookworm (Ancylostoma duodenale & Necator americanus)

Answer 11

L3 stage infective, skin in foot - blood-heart-lungs-intestine

Eggs passed in faeces
Hatch, molt & develop to L3 larva outside of host in the soil
L3 larva is infective stage Penetrates skin of foot
Blood system to heart to lung
Move to pharynx & wallowed
Mature to adult in intestine
Attached to intestinal wall

Life span 1-2 years

Question 12

Host signalling for life cycle example

Answer 12

Strongyloides: evidence that resumption of development is regulated by the insulin-signaling pathway

Question 13

Parasite immune evasion strategy example

Answer 13

Block TH1/17 response (inflammatories INF-y, TNF-alpha, IL2, 12 &17)

Causes TH2 response (anti-inflammatory, IL4, 5, 13 & 10, TGF-beta and IgE)
- may be ES fractions - IL4-dependent

Question 14

How employ immune evasion strategy (nematodes)?

Answer 14

Excreted-secreted (ES) protein fractions

Question 15

ES immune evasion strategy examples specific

Answer 15

Schistosoma mansoni w-1 (T2 Rnase glycoprotein)

Strongyloides ratti Sra-HSP-17.1, 17.2

Fasciola hepatica FhHDM-1

Brugia macrophage migration inhibitory factor (MIF), acts synergistically with IL-4 to suppress pro-inflammatory activation of macrophages

Brugia secretes a TGF-b that can bind host receptor to promote generation of regulatory T cells

H. polygyrus secrets a TGF-b-like mimic that induces Foxp3+ expression in activated T cells

Proteases – involved in tissue invasion, also degradation of host cytokines

Protease inhibitors, e.g Cystatins & Serpins (immunomodulatory properties)

Glycans, lipids, small molecules

Question 16

Categories of ES immune evasion strategy examples specific

Answer 16

Parasite-encoded cytokine homologues
TGF-beta-like proteins
Proteases 
Protease inhibitors
Glycans, lipids, small molecules

Question 17

Hygiene Hypothesis

Answer 17

Proposed to explain rise in allergy and autoimmune disease

Exposure to pathogens promotes immune tolerance

Coevolution of immune system with pathogens

Being too clean leads to a ‘disordered’ immune system

Question 18

Autoimmune treatment parasites

Answer 18

Multiple sclerosis treated with Trichuris suis live parasite or products / Suppression of pathology in mouse models

Inflammatory Bowel Disease
Suppression of colitis by submucosal administration of Trichinella spiralis TSp53 protein