Small Ruminant Parasites

Question 1

What is the infective stage of haemonchus contortus?

Answer 1

L3

Question 2

what are the 3 abomasal nematodes in SR?

Answer 2

1. haemonchus contortus
2. Teladorsagia spp.
3. Trichostrongylus axei

Question 3

T/F: Trichostrongylus axei is the only trichostrongyle of the abomasum

Answer 3

true

Question 4

What are 4 small and large intestinal nematodes of importance in SR?

Answer 4

1. Trichostrongylus spp.
2. Cooperia spp.
3. Oesophagostonum spp.
4. Trichuris spp.

Question 5

Which parasites cause parasitic gastroenteritis (PGE) in sheep and goats?

Answer 5

ALL parasites except haemonchus
they cause slow growth, weight loss, and reduced production of milk/wool/meat

Question 6

why are sheep more at risk for getting internal parasites than goats?

Answer 6

behavior!
goats are browsers and sheep are grazers.
parasites cannot be any higher than 4 inches from the ground, so sheep are at higher risk due to grazing at this level.

Question 7

Between sheep and goats, which is SLOWER to develop immunity to internal parasites?

Answer 7

goats.

Question 8

T/F: the more parasites there are in an individual, the more likely this individual is to suffer negative consequences.

Answer 8

true

Question 9

how do SR obtain GI parasites?

Answer 9

ingest the larvae while grazing

eggs are passed in manure and develop to L3 which gets ingested by the sheep/goat in the pasture

Question 10

Describe the ‘negative binomial distribution’ of parasites within the SR population.

Answer 10

Most of the individuals have few/no parasites
Only few of the individuals have most/a lot of parasites
(70/30 rule) parasite populations in animals are aggregated.

Question 11

What were some of the early recommendations that lead to selection of populations of nematodes that are RESISTANT to anthelmintics and decreased refugia?

Answer 11

• deworm ALL animals at same time
• deworm when fecal exams are +
• deworm regularly (q3-6m)
• rotate antiparasitic drugs
• place animals onto clean pasture after deworming

Question 12

what is the goal of intergral parasite management (IPM)?

Answer 12

keep worms at a level that does NOT have detrimental health effects
this includes more factors than only anthelmintic tx.

Question 13

what are the 3 basic principles of IPM?

Answer 13

1. reduce exposure of hist to infective stages (grazing management)
2. develop more favorable response to host GI parasite infection
3. deworming

Question 14

what things can you do to positively influence grazing management for IPM?

Answer 14

1. limit pasture exposure
2. dry the pasture and produce hay to kill larvae
3. decrease stocking rate
4. do not allow sheep to graze on pastures previously used by goats
5. increase rest time of the pasture and rotate them.

Question 15

When is immunity to GI parasites fully developed?

Answer 15

in mature animals
so first lactation animals are STILL vulnerbale.
Dry, non-pregnant ewes/does are most immune.

Question 16

Describe the difference between resilient animals vs resistant animals

Answer 16

resilient = little or no indicators of parasitism but have HIGH FEC

resistant = LOW FEC, LOW FAMACHA, and rarely require deworming.

Both of which are heritable.
We want to select for RESISTANT animals.

Question 17

T/F: goats are more resilient than sheep

Answer 17

true

Question 18

T/F: you should cull highly susceptible animals as a part of IPM.

Answer 18

true – cull animals with high FAMACHA and high FEC.
this will help select for resistant animals.

Question 19

T/F: there are no FDA-approved macrocyclic lactones for use in goats.

Answer 19

true – benzimidazoles and nicotinic agents are.
the MLs are approved for use in sheep though.

Question 20

What are management factors that could speed up development of resistance and decrease refugia?

Answer 20

1. frequent deworming
2. using same drug/group
3. anthelmintic underdosing
4. mass treatment
5. purchase/movement of new animals

Question 21

Define refugia

Answer 21

the proportion of a parasite population that remains susceptible to a dewormer.

Question 22

How can we integrate the concept of refugia into our deworming protocol?

Answer 22

ONLY treat animals that need it based on FAMACHA and FEC.
Never deworm all animals.
(Targeted Selective Treatment)

Question 23

T/F: FAMACHA is only used for trichostrongyle infections

Answer 23

false – H. contortus
it measures the degree of anemia to inform treatment decisions (only anemia animals grade 4-5 +/- 3 are treated)

Question 24

Why do FEC not always accurately reflect the GI nematode population?

Answer 24

1. some genera produce more eggs than others (haemonchus>teladorsagia)
2. egg production/female is inversly related to population (teladorsagia)
3. when immunity develops, egg production decreases
4. FEC is altered by food and feces consistency

Question 25

T/F: Targeted selective treatment decreases refugia

Answer 25

false -- it increases it and slows the rate of developing anthelmintic resistance because it allows only for treatment of animals that are suffering consequences of parasitism.

Question 26

T/F: goats require higher doses of anthelmintics than sheep do because they metabolize drugs differently.

Answer 26

true