5. Anti-helminthics

Question 1

Describe the classification of helminths

Answer 1

1. Nematodes (roundworm)
   - Blood and tissue
   - Intestinal
2. Cestodes (tapeworms)
   - Taenia (human host)
   - Echinococcus (human is an accidental host)
3. Trematodes (flukes)
   - Lungs
   - Liver
   - Blood

Question 2

4 main pathological mechanisms of helminths

Answer 2

Inflammation
Competition for nutrients
Space occupying lesions
Stimulation of fibrosis

Question 3

Name 4 Nemotode helminths found in the intestines

Answer 3

Ascaris
Hookworm
Enterobius
Trichiuris

Question 4

Transmission of helminths?

Answer 4

Faecal-oral
Vector
Direct invasion

Question 5

4 types of host?

Answer 5

Definitive
Intermediate
Accidental
Parathenic

Question 6

4 examples of helminth vector?

Answer 6

Flies, Aedes mosquito, crysops and snails

Question 7

What is the consequence of repeated cycles of inflammation and bacterial infection in acute lymphoedema?

Answer 7

Elephantiasis

Question 8

Clinical features of trichiuris?

Answer 8

• Vague abdominal symptoms
• Trichiuris dysentery syndrome 
• Growth retardation
• Intellectual compromise
-micronutrient deficiency 
-mucosal integrity

Question 9

Clinical features of hookworm?

Answer 9

Anaemia due to blood usage

Vague abdominal pain

Question 10

Ascaris clinical features?

Answer 10

Vague abdominal pain
Intestinal obstruction
Hepatobiliary obstruction and jaundice

Question 11

Competition for nutrients, name 4 helminthis in which this is their main pathological mechanism?

Answer 11

• Hookworms
• Ascaris
• Tapeworms
• Trichiuris trichiura

Question 12

Space occupying lesions?

Answer 12

• Eggs in the wrong place
• Cysticercosis causing CSF obstruction
• Ascaris causing intestinal obstruction

Question 13

What pathology’s are caused by parasites being in the liver, brain and CSF

Answer 13

Cysticercus causing CSF block
Hydatid cyst in the liver
Cerebral cysticercosis in the brain (leading to seizures)

Question 14

What is the consequence of schistosomiasis?

Answer 14

In schistosomiasis, eggs trapped in the tissues produce granulomatous inflammatory reactions, fibrosis, and obstruction.

Question 15

What is the result of fibrosis associated with tissue schistosomes?

Answer 15

Leas to inflammation and fibrosis….
Lung fibrosis –> Right HF
Liver fibrosis –> Portal hypetension
Bladder fibrosis –> Bladder cancer

Question 16

What is the general treatment for helminth infections associated with the following pathogenesis:
• Inflammation
• Competition for nutrients 
• Space occupying lesions
• Stimulation of fibrosis

Answer 16

Inflammation
• Anti-inflammatory eg., steroids

Competition for nutrients
• Reduce worm burden and support nutrition

Space occupying lesions
• Surgery, decompression

Stimulation of fibrosis
• Helminth eradication and treatment of secondary effects

Question 17

Treatment of cestode classified helminths?

Answer 17

Praziquantel

Question 18

Due to the problems of the cysticercosis, what must be combined with anti-helminthic treatment of cestodes?

Answer 18

Continue anti-epileptic drugs

+ Steroids

Question 19

Treatment of nematodes classified helminths?

Answer 19

Albendazole mainly

[Levamisole and piperazine are rarely used]

Question 20

Praziquantel:
Mechanism?
Treats which diseases?
Properties?
Side effects on neuro, GI, Liver and skin?
Drug interactions?

Answer 20

Mechanism: Probably increases calcium permeability of membranes depolarising them. May interfere with purine synthesis

Treats:
• Hydatid disease
• Cysticercosis
• Schistosomiasis
• Clonorchis, Fascioliasis and Paragnomiasis infection

Properties:

• Well absorbed orally
• Low systemic conc
• Excreted in the kidneys
• Short half life

Side effects:
Neural: Dizziness, headache, drowsiness and somnolescence
GI: Abdominal cramps and nausea. Diarrhoea
Liver: Transient asymptomatic rise in transaminases
Skin: Urticaria, rash and pruritis

Drug interactions:
Interacts with rifampicin (decreased concentrations), carbamazine, phenytoin (reducing praziquantel bioavailability)

Question 21

Albendazole:
Classification?
Used for treatment of which nematode?
Used for treatment of which protozoa?
Used for treatment of which Cestoda infections?
Mode of action?
Where is it concentrated?
Side effects?

Answer 21

Classification: A benzimidazole

Treatment of nematode infections: trichiuriasis, filariasis, Enterobius infection, ascariasis, hookworm, toxocariasis, strongyloidiasis

Treatment of some protozoa: giardia

Treatment of some cestode infections: Neurocysticercosis
and hydatid disease

Mode of action:

1. Binds to colchicine sensitive receptor or tubulin. Prevents polymerisation into microtubules.
2. Impaired glucose uptake and depleted glycogen stores
3. Degenerative changes appear in the worm

Concentrated in semen and may be teratogenic

Side effects:
• Persistent sore throat
• Headaches dizziness and seizures
• Acute liver failure
• Aplastic anaemia and marrow suppression

Question 22

Piperazine as a treatment for helminths?

Answer 22

• Agonist activity against the gamma butyric acid receptor paralysing muscular activity
• Orally active
• Metabolism in liver
• Variable half life
• Used to treat ascariasis and enterobius infection
• SE include GI tract upset and rarely hypersensitivity, dizziness

Question 23

What drug replaces levamisole and pyrantel

Answer 23

Albendazole as it’s less toxic

Question 24

Helpful use of diethyl carbamazine?

Answer 24

Causes worms to come to skin surface for diagnosis by biopsy.

Features:
• A piperazine derivative
• WHO essential medicine list
• Inhibits arachidonic acid making parasites more susceptible to immune attack
• Filaria infection
• Associated with increase in inflammation: caution Mazzotti reaction, loss of site in onchocerciasis

Question 25

Ivermectin:
Mode of action?
Active against?
Complicated by?
How is absorption increased pass the BBB?

Answer 25

• Ivermectin binds glutamate-gated chloride increase in the permeability of the cell membrane to chloride ions with hyperpolarization of the nerve or muscle cell resulting in paralsysis and death of the parasite either directly or by causing the worms to starve.
• Active against fliarial worms, lice, scabies and bed bugs
• Complicated by CNS depression
• Increased risk of absorption past the blood brain barrier of HIV protease inhibitors, calcium channel blockers and glucocorticoids

Question 26

Niclosamide:
Mechanism?
Treats?
Side effects?

Answer 26

Mechanism: Inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism
Treats: Used for the treatment of tape worm infections only
Side effects: Causes dizziness, skin rashes, drowsiness and perianal itching.

Question 27

Prevention and control of intestinal helminths

Answer 27

• Vector control for filariasis
• Meat inspection for cysticercosis
• Sanitation and hygiene for intestinal nematodes

Question 28

Examples where inflammation

is the main pathogenic mechanism

Answer 28

• Filariasis
• Onchocerciasis ( in eye leading to blindness)
• Toxocariasis (generalised inflammation all over body)
• Cysticercosis
• Schistosomiasis
• Enterobius

Question 29

How many lobes should a neutrophil have? Pathology leading to excess lobes?

Answer 29

Should have 4

If more, sign on anaemia

Question 30

Cells in the stomach involved in gastric acid production

Answer 30

The stomach has a mucus cell lining, parietal glands an pyloric glands.
The parietal cells secrete HCl, pepsinogen, IF, mucus.
Whilst pyloric glands secrete mucus for protection and gastrin which stimulates ECL cells.

Question 31

3 modes of transmission of helminths?

Answer 31

Faecal oral (Ascaris)
Vector (filariasis)
Direct invasion (Schistosomiasis)