Lecture 15-16 Epi of Trichostrongyles Flashcards
What are the trichostrongyles of sheep that occur in the abomasum? (3)
Haemonchus contortus Ostertagia circumcincta Trichostrongylus axei
What are the trichostrongyles of cattle that occur in the abomasum? (3)
H. placei
O. ostertagi
T. axei
What are the trichostrongyles of sheep that occur in the small intestine? (2)
Trichostrongylus spp. Nematodirus spp.
What are the trichostrongyles of cattle that occur in the small intestine (2)
Cooperia spp.
N. helvetianus
What are two economic losses caused by gastrointestinal nematodes and an example of each
Production losses • fleece weight and staple strength • ewe live weight and fertility • lamb growth rate • ↓weaning weight - increased deaths Increased expenses • treatment and monitoring
what are three stages you can target control of parasites at
parasitic stage (anthelmintics, vax, nutrition) contaminating stage (strategic drenching, rotational grazing) infectious stage (pasture spelling, reduced stocking)
what are 5 factors the epi of trichostrongyloidosis depends on?
- Moisture
- Temperature
- Grazing factors
- Host factors
- Management factors
how can moisture affect movement of parasites?
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
how does temperature impact trichostrongyles
- 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
in terms of moisture, what does T. vitrinus vs T. rugatus like
T. vitrinus- wet
T. rugatus- dry
what is the rule about parasitic infections in ruminants
mixed infections!- parasitic infections with different genera are synergistic in their pathogenic effects.
what are the two main assumptions about parasites in ruminants
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.
What grazing factors influence worm burdens?
- 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)
what host factors influence worm burdens
- age
- inherited susceptibility (genetic)
- negative bionomical distribution: most sheep have few worms, few sheep have high burden
- must sample at least 10 sheep
what does preparturient rise in fecal egg counts mean
inc in FEC in ewes just prior to lambing and for first 4-6 weeks of lactation
what can preparturient rise in FEC be due to
re emergence of inhibited larvae
existing worm burden becomes more fecund because of relaxed immunity
what management factor influence worm burdens
time of lambing- autumn lambing-> increased issues with parasites
what is hypobiosis
arrested development of parasite at the L4 stage INSIDE the host
what are factors supporting hypobiosis
- unfavorable climatic conditions
- immune status of animals
- Density of GINs
Factors supporting the resumption of the development of inhibited larvae
• hormonal changes
• alterations in the components of immune system
during the PPR
• density dependence of parasite
what does the history of an animal with a high parasite burden usually include
scouring (can be due to many causes) and noticeable “tail to the mob”
-dag scoring
What is an indirect method of diagnosis of parasites
FEC- rough guide to level of infection (cannot id genera)
fecal cultures (can identify genera)
- both can be performed ante mortem
what parasites are high egg producers and what does this have to do with FEC
haemonchus (5000/female/day) and Oesophagostomum (3000) have high correlation bewteen eggs and worms
- low egg producers have a low correlation
what does FEC not account for and what else is it affected by
male worms, encysted larvae, developing adults or immunological suppression of egg output
- rate of passage and water content of feces (diarrhea reduces egg counts)
what is a direct method of diagnosis of parasites
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
what is the most important genus as 5000 to 10000 can be fatal
haemonchus
how many worms of trichostrongylus causes production loss? death?
10000
80000-100000
what is the threshold level to recommend treatment after a FEC
> 500 epg (eggs per gram of feces) is pathogenic
what tests can be used to diagnose haemonchus
PCV, RBC and WBC counts (any blood sucking worm)
FAMACHA- measures level of anemia (small herd size)
what are two ways to measure pasture larval counts
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
what are 4 methods of control of trichostrongyloidosis
- 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)
explain smart grazing for merino weaners
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)
what is a trichostrongyle in the horse and where does it occur
T. axei in the stomach
what are two trichostrongyles in the pig, where
T axei and hyostrongylus rubidus are both in the stomach
what species does hyostrongylus affect, life cycle, PPP, where is L3, what does it cause and how can it be controlled
pigs in the stomach
direct life cycle
L3 in gastric glands PPP = 21 days
causes diarrhea, weight loss controlled on concrete floors
what is a trichostrongylus of a cat and where does it occur
Ollulanus tricuspis (stomach)
what species does ollulanus tricuspis affect, what size, female ID, pathogenicity (high/low), transmission
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
what are two trichostrongylus that occur in birds
Amidostomum anseris
(gizzard worm)
Trichostrongylus tenuis
