Gut parasites of ruminants

Question 1

What are the most important gut parasites of sheep?

Answer 1

• abomasum:
  
  • Haemonchus contortus
  • Teladorsagia circumcinta
  • Trichostrongylus axei
• SI:
  
  • Nematodirus battus
  • Trichostrongylus spp

Question 2

What are the most important gut parasites in cattle?

Answer 2

• abomasum:
  
  • ostertagia ostertagi
• SI
  
  • Cooperia oncophora

Question 3

What is the normal lifecycle of the gut nematode?

Answer 3

• eggs passed out into pasture
• develop to L3
• then ingested by grazing ruminants
• undergo 2 moults
• go to intestine
• mate
• eggs

Question 4

What is bovine ostertagiosis?

Answer 4

• Infect gastric glands in abomasum, mature on mucosal surface
• PPP = 3 weeks
• takes 2 grazing seasons to develop immunity (not complete)
• worldwide
  
  • Type I - calves, first grazing season, on pasture with larvae
    
    • profuse, watery, green diarrhoea
    • Mid - July - 3/4 weeks after infection
    • low mortality
  • Type II
    
    • yearlings
    • winter/spring
    • larvae that had been ingested in autumn - gone into arrest - hypobiosis
    • high mortality
    • poor response to treatment
    • diarrhoea, thirst, anorexia

Question 5

What is hypobiosis?

Answer 5

• larvae arrest in L3/4
• ruminants and horses
• metabolic rate decreases

Question 6

What initiates the hypobiosis?

Answer 6

• over crowding
• internal genetic/ enviro clock?
• host immune response

Question 7

Why is hypobiosis important?

Answer 7

• survive hostile environment
• more resistant to anthelmintics
• serious outbreaks
• pasture contamination

Question 8

WHat is the mechanism of pathogenesis of ostertagiosis?

Answer 8

• larvae increase 100 fold in gastric glands
• get necrosis of the secretory ep, swelling of the gland and loss of secretory cells
• Parietal cells loss - less HCl secreted - increase pH, loss of bacteriocidal properties - protein digestion down
• Peptic cell loss - less pepsinogen - lower protein digestion
  
  • osmotically active contents in lumen - fluid transfer - diarrhoea
  • increased permeability of gut - so peptinogens out and plasma proteins in - hypoalbuninaemia

Question 9

In dairy when do Type I and II diseases occur?

Answer 9

• I = July-Oct
• II = winter and early spring

Question 10

What is the epidemiology in beef herds?

Answer 10

• Spring calving - ostertagiosis uncommon - immune adults dont produce many eggs/ die before many larvae can be ingested
• Autumn/ winter calving - common in following grazing season

Question 11

What does Cooperia oncophera cause?

Answer 11

• inappentance, lower weight gain in calves
• 1 grazing season for partial immunity
• adults develop on intestinal mucosa

Question 12

Which animals are most affected by Nematodirus battus?

Answer 12

• SI - lambs
• L3 in eggshell
• need prolonged chill to hatch then >10 degrees
• invade intestinal mucosa - then 2 moults - in the lumen

Question 13

Pathogenesis of nematodirus battus?

Answer 13

• larvae
• destroy villi and mucosa
• villus atrophy and fusion
• impaired ability of the intestine to exchange fluid and nutrients

Question 14

Clinical signs and diagnosis for Nematodirus battus?

Answer 14

• green-yellow diarrhoea
• inappentence
• low growth rates
• dehydration
  
  • carcass dehydrated, acute enteritis, thin twisted worms >10000

Question 15

Epidemiology of Nematodirosis?

Answer 15

• L3 survive long time on pasture
• if lambs grazing coincides with this - infection (May, June)
• lamb-lamb transmission
• cool, wet summers increase it

Question 16

What are the signs of teladorsiagia circumcincta in sheep?

Answer 16

• ostertagiosis
• similar to type I bovine
• intermittent diarrhoea, weight loss, poor protein and fat depostition (lambs)
• July-Sept - immunity relaxed at this time
• immunity acquired slowly - 2 grazing seasons

Question 17

What is haemonchosis?

Answer 17

• haemonchus contortus
  
  • larvae exsheath in lumen and moult 2x in gastic glands
  • female - barbers pole
  • before final moult - piercing lancet - blood from mucosal vessles
  • no acquired immunity

Question 18

Clinical features of haemonchus?

Answer 18

• acute - aneamia, loss of rbc packed volume, reduced iron and protein to GIT, weight loss, inappentence, sub-mandibular oedema, falling wool, dark coat colour
• chronic - increased blood loss, weight loss, weakness

Question 19

Describe the epidemiology of Haemonchus contortus

Answer 19

• high temp/ humidity needed
• ingested in summer
• normally arrest - so next spring
• if dont then late summer

Question 20

How would you tell between strongyl eggs and Nematodirus eggs?

Answer 20

• N. battus = 160 um
• Strongyle = 80 um

Question 21

What other tests could be done?

Answer 21

• Ostertagiosis and haemonchus - higher pepsinogen levels
• Haemonchus - lower packed rbc, anaemi, lower iron

Question 22

What are SCOPS principles?

Answer 22

• fully effective treatment
• dont bring resistant worms on farm
• dont allow seletion of resistant worms
• reduce reliance of anthelmintics

Question 23

What is COWS policies?

Answer 23

• control of worms sustainable
  
  • grazing - newly seeded, hay/silage used second half, mixed/sequential
  • anthelmintics - strategic (target and limit pasture contamination), thereuptic - target groups suffering production losses, treat housing

Question 24

What is rumen fluke?

Answer 24

• trematodes
• young - in duodenum
• older - forestomachs
• intermediate host = water snails (plenorbia)
• disease = high amount in intestine
• more common
• anorexia, diarrhoea, anaemia

Question 25

What are the tapeworms that infect?

Answer 25

• Moniezia benedeni, M.expansa
• adults in SI
• not highly pathogenic - can occlude SI lumen in lambs
• depends on lifecycle of oribatid mite
• eggs passed out of SI, ingested by oribatid mites, cysticeroid develops in mite, eaten by cow etc