Resistance

Question 1

Define resistance.

Answer 1

Greater freq of individuals in a pop that tolerate treatment than in a normal pop of the same species & is heritable.

Question 2

Define refugia.

Answer 2

-stages of a parasite species not exposed to drugs
>eggs & larvae in environment
>larvae & adults in untreated animals
-less refugia = more resistance
[killing only some worms relieves clinical signs]
*put on new pasture, leave for a week THEN treat to keep a low exposure (not the other way around) = optimal low exposure
*treat, leave for a week & move = ok option

Question 3

Describe approaches that decrease refugia.

Answer 3

-treating when few larvae on pasture (drought)
-treating all animals at same time
-frequent deworming
-Anthelmintics with residual activity

Question 4

Describe resistance.

Answer 4

-inevitable consequence
-resistance to one drug = resistance to others in the same class
-largest threat to livestock
-resistance w almost all trichostrongylids

Question 5

Describe the integrated parasite management. (IPM)

Answer 5

-slow down rate of resistance
-animals never parasite free
-prevent clinical disease & production losses
-maintain parasite below economic threshold
-reassess 1-2yr

Question 6

Describe IPM selective treatment.

Answer 6

-70-80% untreated 20% treated
-FAMACHA, FEC, age, susceptibility, weight gain, etc
-decrease Anthelmintics use & protect refugia
*FAMCHA = sheep & goats suffering from Haemonchus contortus
>5 point check: eye, body, rear, jaw, nose
*FEC = McMaster - identify high egg producers -> pasture contamination
>high shedding doesnt mean disease

Question 7

Describe the IPM fecal egg counts.

Answer 7

-EPG of feces; McMaster
-identify high egg producer = pasture contamination
high shedding doesnt equal disease!
LIMITATION:
-cant distinguish eggs
-not correlated to severity of disease or worm#

Question 8

Describe IPM breeding.

Answer 8

-breed for host resistance
>decreased parasite estab
>decreased fecundity
-breed for host resilience
>ability to tolerate infection
-genetics of host resistance & resilience NOT related

Question 9

Describe IPM nutrition.

Answer 9

-support immune system
-decrease parasite estab
-decrease fecundity
(pasture forage & micronutrients)

Question 10

Describe IPM pasture management.

Answer 10

-rotational grazing
>of livestock
>leaders-followers
-resting pasture
-mixed grazing
-crop/grazing rotations

Question 11

Describe IPM anthelmintic efficacy.

Answer 11

-% egg reduction
-(pretreatment FEC-posttreatment FEC)/pretreatment FEC
-test 10-14d post treatment