Anthelmintics Flashcards
How are anthelmintics often classified?
- Spectrum of activity
- Chemical group/mode of actin
- Target parasites
- Method of delivery
What are the main groups of anthelmintics and their drench colours?
Benzimidazoles - white dreched
Imidazothiazoles - yellow drenches
Macrocyclic lactones - clear drenches
How do the three main anthelmintic groups work?
BZ - Bind to tubulin thus preventing glucose uptake from the gut. They kill over a period of days so the longer then last the more potent they are
LV - They are cholinergic agonists so cause a spastic paralysis
ML - They open glutamate - chloride channels in the post synaptic membrane leading to a flaccid paralysis.
How does potency vary for BZs with regard to dose frequency, species and food intake?
Increase potency with multiple small doses, ruminants and horses has a greater potency in than dog, starvation in ruminants for 12-24 hours as decreased motility.
What are the two types of IZ?
Levamisole
pyrantel
What is the spectrum of activity of Levamisole?
Nematodes and lungworms. Activity against hypobiotic larvae is variable dependent on host and parasite species.
What are the main types of ML?
Avermectins (e.g. ivermectin) and milbemycins (e.g. milbemectin & milbemycin)
What parasites do MLs target?
Nematodes - highly effective against all stages
Lungworms
Arthropods - mainly against blood sucking but this is also variable dependent on host/parasite sp.
What is the difference between metaphylaxis and prophylaxis with regard to grazing animals?
Metaphylaxis protects animals grazing contaminated pasture.
Prophylaxis prevents grazing animals from infecting clean pasture.
What is worth considering when treating against tapeworms?
Consider using a narrow spectrum antehelmintic
How does pranziquantal work?
It increases permeability of the tegument of cestodes to Ca. Ca influx causes muscular spasm - spastic paralysis and malabsorption. It also causes disruption of the tegument so the tapeworm is digested.
What are salicylanilides and substituted phenols and how do they work?
These are flukicides but also have effect on blood sucking nematodes e.g. Haemonchus spp. They uncouple oxidative metabolism.
Why do salicylanilides have such a long period of action?
Why is this important in production animals?
They bind to plasma proteins. Don’t use in milking animals as significant quantities enter the milk.
What is the flukicide of choice to treat acute fluke infestatin?
Triclabendazole
What different methods of delivery are there for worming treatments?
Oral -Drench -Paste -Tablet -In feed -bolus Parenteral -SC or IM injection Topical -Spot on/pour on
