Livestock antiparasitics

Question 1

Define WHP…

Answer 1

Witholding period - minimum period of time that must elapse BETWEEN LAST ADMINISTRATION OR APPLICATION of vet chemical product & treated feed & SLAUGHTER OR USE FOR HUMAN CONSUMPTION

Question 2

Define ESI…

Answer 2

Export slaughter interval - the time which should elapse between administration of a veterinary chemical to animals and their slaughter for export.

Question 3

Name 3 broad spectrum sheep anthelmintics (nematode)…

Answer 3

Benzimidazoles (‘white’ drenches)
Levamisole (‘clear’ drenches)
Macrocyclic lactones (IVERMECTIN etc.)

Question 4

Name 3 narrow-spectrum sheep anthelmintics & state what they treat…

Answer 4

closantel - barber’s pole
Triclabendazole - Fasciola hepatica (liver fluke)
praziquantel - cestodes

Question 5

Name 3 cattle anthelmintics…

Answer 5

1. benzimidazoles
2. Levamisole
3. macrocyclic lactones (ivermectin)

Question 6

Name 3 equine anthelmintics…

Answer 6

1. benzimidazoles
2. Tetrahydropyramidines (THP’s) - pyrantel
3. praziquantel - (tapeworms/cestodes/flatworms)

Question 7

Name 2 flukicides…

Answer 7

Triclabendazole

Flukazole

Question 8

Name an injectable flukicide for cattle

Answer 8

Nitromec - nitroxynil + clorsulon

Question 9

Discuss the factors that lead to selection for anthelmintic resistance…

Answer 9

• resistance occurs when there is a greater frequency of individuals within a population able to tolerate doses of [a] compound than in a normal population of the same species
• resistance will develop when individual worms are able to survive drug treatment, then pass on their genes to subsequent generations
• Subsequent generations also need to be subjected to drug selection. Ultimately there are sufficient numbers of resistant worms to successfully breed with each other

Question 10

How would you test for anthelminthic resistance?

Answer 10

Fecal Egg Count Reduction Test (FECRT)
Worm egg count (WEC) & find wormy [young] animals to test
treat some & not others (control)
resample & WEC/larval diff within PPP
check reduction in WEC = drench efficacy

Question 11

How does anthelminthic resistance develop?

Answer 11

high treatment frequency
Underdosing
Using ineffective products
Poor treatment technique
Poor quarantine protocol
Blanket drenching of all sheep on the farm

Question 12

Major anthelmintic groups for sheep and current resistance levels for these groups… (Benzimidazoles ‘white’ drenches)

Answer 12

More than 90% of farms with resistant worms

Question 13

Major anthelmintic groups for sheep and current resistance levels for these groups… Clear (levamisole) drenches

Answer 13

More than 90% of farms with resistant worms

Question 14

Major anthelmintic groups for sheep and current resistance levels for these groups… BZ/lev combination drenches

Answer 14

More than 60% of farms with resistant worms

Question 15

Major anthelmintic groups for sheep and current resistance levels for these groups… Closantel

Answer 15

Definite resistance in barber’s pole worm

Question 16

List some chemical groups that treat sheep blow fly…

Answer 16

organophosphates - diazinon (only for individual sheep treatment)
insect growth regulators - dicyclanil
macrocyclic lactones - ivermectin

Question 17

All lice info in ‘ruminant ectoparasites’ para lecture…

Answer 17

only 1 additional slide in pharma

Question 18

List some chemical groups for sheep body lice treatment

Answer 18

organophosphates - diazinon
macrocyclic lactones - ivermectin
insect growth regulators - triflumuron