Lecture 15-16 Epi of Trichostrongyles

Question 1

What are the trichostrongyles of sheep that occur in the abomasum? (3)

Answer 1

Haemonchus contortus Ostertagia circumcincta Trichostrongylus axei

Question 2

What are the trichostrongyles of cattle that occur in the abomasum? (3)

Answer 2

H. placei
O. ostertagi
T. axei

Question 3

What are the trichostrongyles of sheep that occur in the small intestine? (2)

Answer 3

Trichostrongylus spp. Nematodirus spp.

Question 4

What are the trichostrongyles of cattle that occur in the small intestine (2)

Answer 4

Cooperia spp.

N. helvetianus

Question 5

What are two economic losses caused by gastrointestinal nematodes and an example of each

Answer 5

Production losses
• fleece weight and staple strength
• ewe live weight and fertility
• lamb growth rate
• ↓weaning weight - increased
deaths
Increased expenses
• treatment and monitoring

Question 6

what are three stages you can target control of parasites at

Answer 6

parasitic stage (anthelmintics, vax, nutrition)
contaminating stage (strategic drenching, rotational grazing)
infectious stage (pasture spelling, reduced stocking)

Question 7

what are 5 factors the epi of trichostrongyloidosis depends on?

Answer 7

1. Moisture
2. Temperature
3. Grazing factors
4. Host factors
5. Management factors

Question 8

how can moisture affect movement of parasites?

Answer 8

lateral movement is limited and assisted by heavy rains and floods
vertical movement can be up to 7 cm- larvae will move up grass blades in the morning in the hopes of being ingested by a host

Question 9

how does temperature impact trichostrongyles

Answer 9

• mild Australian temperatures have little effect except: Haemonchus >10o C
• low temperature can slow egg hatching & development in some species
• high temperatures shorten survival times of L3’s on pasture

Question 10

in terms of moisture, what does T. vitrinus vs T. rugatus like

Answer 10

T. vitrinus- wet

T. rugatus- dry

Question 11

what is the rule about parasitic infections in ruminants

Answer 11

mixed infections!- parasitic infections with different genera are synergistic in their pathogenic effects.

Question 12

what are the two main assumptions about parasites in ruminants

Answer 12

i. All sheep are infected all the time
ii. Eradication is impossible, therefore try to control infections.
Eradication would lead to totally susceptible sheep, ie no immunity.

Question 13

What grazing factors influence worm burdens?

Answer 13

• sheep do not use paddocks uniformly (use indicated by fecal deposits)
• sheep graze selectively
• stocking rates affect parasite densities (higher= more parasites, too high= larvae exposed and die)

Question 14

what host factors influence worm burdens

Answer 14

• age
• inherited susceptibility (genetic)
• negative bionomical distribution: most sheep have few worms, few sheep have high burden
• must sample at least 10 sheep

Question 15

what does preparturient rise in fecal egg counts mean

Answer 15

inc in FEC in ewes just prior to lambing and for first 4-6 weeks of lactation

Question 16

what can preparturient rise in FEC be due to

Answer 16

re emergence of inhibited larvae

existing worm burden becomes more fecund because of relaxed immunity

Question 17

what management factor influence worm burdens

Answer 17

time of lambing- autumn lambing-> increased issues with parasites

Question 18

what is hypobiosis

Answer 18

arrested development of parasite at the L4 stage INSIDE the host

Question 19

what are factors supporting hypobiosis

Answer 19

• unfavorable climatic conditions
• immune status of animals
• Density of GINs

Question 20

Factors supporting the resumption of the development of inhibited larvae

Answer 20

• hormonal changes
• alterations in the components of immune system
during the PPR
• density dependence of parasite

Question 21

what does the history of an animal with a high parasite burden usually include

Answer 21

scouring (can be due to many causes) and noticeable “tail to the mob”
-dag scoring

Question 22

What is an indirect method of diagnosis of parasites

Answer 22

FEC- rough guide to level of infection (cannot id genera)
fecal cultures (can identify genera)
- both can be performed ante mortem

Question 23

what parasites are high egg producers and what does this have to do with FEC

Answer 23

haemonchus (5000/female/day) and Oesophagostomum (3000) have high correlation bewteen eggs and worms
- low egg producers have a low correlation

Question 24

what does FEC not account for and what else is it affected by

Answer 24

male worms, encysted larvae, developing adults or immunological suppression of egg output
- rate of passage and water content of feces (diarrhea reduces egg counts)

Question 25

what is a direct method of diagnosis of parasites

Answer 25

total worm count (post mortem)- can only perform on 1-2 sheep from “tail of the mob”
- get direct estimate of numbers of individual genera

Question 26

what is the most important genus as 5000 to 10000 can be fatal

Answer 26

haemonchus

Question 27

how many worms of trichostrongylus causes production loss? death?

Answer 27

10000

80000-100000

Question 28

what is the threshold level to recommend treatment after a FEC

Answer 28

> 500 epg (eggs per gram of feces) is pathogenic

Question 29

what tests can be used to diagnose haemonchus

Answer 29

PCV, RBC and WBC counts (any blood sucking worm)

FAMACHA- measures level of anemia (small herd size)

Question 30

what are two ways to measure pasture larval counts

Answer 30

Direct quantification from pasture
• estimate no of larvae/kg of herbage
• slow
• does not detect low levels of contamination*
• non random distribution of larvae in paddock
makes sampling difficult
• can be useful in comparing paddocks
Introduction of worm-free ‘tracer’ animals
• mimic the grazing patterns of the resident flock
• costly
• time consuming
• not all ingested larvae develop into adults

Question 31

what are 4 methods of control of trichostrongyloidosis

Answer 31

• paddock spelling (effective over summer)
• crops (sowing paddock, use of stubbles)
• Alternate grazing (sheep and cattle- except t axei)
• Use of anthelmintic drugs (effective in summer in southern aus- 1 at start and 1 at end)

Question 32

explain smart grazing for merino weaners

Answer 32

pick a paddock
deworm sheep and overgraze that paddock
spell paddock for 2-3 months
treat flock again and overgraze
don't graze for a month
bring in weaners for their first winter to this paddock with no worms (worms are highest in winter)

Question 33

what is a trichostrongyle in the horse and where does it occur

Answer 33

T. axei in the stomach

Question 34

what are two trichostrongyles in the pig, where

Answer 34

T axei and hyostrongylus rubidus are both in the stomach

Question 35

what species does hyostrongylus affect, life cycle, PPP, where is L3, what does it cause and how can it be controlled

Answer 35

pigs in the stomach
direct life cycle
L3 in gastric glands PPP = 21 days
causes diarrhea, weight loss controlled on concrete floors

Question 36

what is a trichostrongylus of a cat and where does it occur

Answer 36

Ollulanus tricuspis (stomach)

Question 37

what species does ollulanus tricuspis affect, what size, female ID, pathogenicity (high/low), transmission

Answer 37

Cat in the stomach
minute nematode (1 mm)
female has a tail with 3-4 short cusps viviparous (L3 develops within uterus) not very pathogenic
transmitted in vomit

Question 38

what are two trichostrongylus that occur in birds

Answer 38

Amidostomum anseris
(gizzard worm)
Trichostrongylus tenuis