B2 Ectoparasites 1E

Question 1

What is malathion and how does it work ?

Answer 1

Anticholesterase- works by blocking the action of the enzyme cholinesterase which is required for the hydrolysis of cholenesterate at the neuromuscular junction (neuromuscular toxin)

Question 2

Where does malathion act on in the animal ?

Answer 2

Nervous system

Question 3

Does malathion irreversibly or reversible bind to block cholinesterase ?

Answer 3

Irreversibly

Question 4

What is the consequence of malathion binding to cholinesterase ?

Answer 4

Prolonged post-ganglion if neuronal excitation causing continuous muscle excitation and contraction

Question 5

How toxic is malathion in humans ?

Answer 5

Low toxicity but repeat exposure and over usage is toxic

Question 6

Is ingesting malathion more toxic or less toxic than normal and why ?

Answer 6

More toxic due to it being metabolised (oxidised) to malaoxon

Question 7

What are the muscarinic (parasympathetic) effects of malathion/malaoxon poisoning ?

Answer 7

• mitosis (pupillary constriction)
• salivation
• sweating
• bradycardia (slowing of heart rate)

Question 8

What are the nicotine (skeletal muscle, SkM) effects of malathion/malaoxon poisoning ?

Answer 8

Fasciculation (tiwitjcing of SkM)
- spontaneous release of ACh

Paralysis
- depolarising neuromuscular block

Question 9

What are the nervous system symptoms with the use of malathion/malaoxon poisoning ?

Answer 9

• anxiety
• restlessness
• dizziness