Ovine GI nematodes

Question 1

Important disease syndromes caused by sheep GI nematodes

Answer 1

• PGE (Osteragia Teladorsagia + trichostrongylus)
• Nemadatodirus battus
• Hemonchosis

Question 2

Ovine abomasal nematodes

Answer 2

Osteragia (teladorsagia)

Hemonchus

Trichostrongylus **HOT

Question 3

Ovine Small Intestinal nematodes

Answer 3

**Cooperia

**Nematodirus

**Trichostrongylus

Bunostomum

Strongyloides

** = most important

Question 4

Basic Trichostrongyloidea information

Answer 4

Most important group of nematode pathogens in grazing ruminants

• Direct life cycle, L3 infective
• Mainly GI nematodes, except dictylocaulus
• PPP = 21d

Question 5

What is the most important group of nematode pathogens in grazing ruminants?

Answer 5

Trichostrongyloidea

Question 6

List the nematodes in Trichostrongyloidea superfamily

Answer 6

Ostertagia (Abomasum)

Trichostrongylus (abomasum + SI)

Hemonchus (abomasum)

Cooperia (SI)

Nematodirus (SI)

Question 7

Teladorsagia circumcincta life cycle

Answer 7

Eggs hatch in feces –> Mature from L1 to L3 in pasture –> infective L3 ingested –> penetrates abomasal gland –> L4 (can arrest here) –> emerge 18d post ingestion in abomasum –> eggs laid

PPP = 21d, direct

* same as cattle

Question 8

Ovine osteragiosis: Which type is more common?

Answer 8

Type 1 = common

Type 2 = uncommon

Question 9

Clinical signs of Ovine osteragiosis

Answer 9

Weight loss/failure to gain weight

Intermittent diarrhea (less dramatic than cattle)

Appetite loss

Question 10

What causes major pathology in Osteragia?

Answer 10

Larvae emerging from gland

• rupture of intracellular jx
• Destruction of parietal cells
• Decrease HCl secretion
• Increased abomasal pH (2–>7)
• pepsinogen no longer converted to pepsin
• bacterial overgrowth
• Elevated plasma pepsinogen

** same as cattle

Question 11

How to diagnose Ostergia in sheep?

Answer 11

Clinical signs

Predominantly in lambs

Time of year

Fecal egg counts PM

Question 12

Discuss the immunity to Tealdorsagia in sheep

Answer 12

• slow to develop, worm burdens and fecal egg output low in adults except during periparturient period

Question 13

Discuss the periparturient rise in fecal egg output from EWES

Answer 13

• Occurs 2 weeks prior to and 6 weeks after lambing

Due to:

• Increased establishment of overwintered larvae from pasture (take up higher numbers –> patent infection –> eggs) - Inhibited L4s reactivating and developing to adults
• Female worms have increased fecundity (pasture more highly contaminated

Question 14

Draw the epidemiology of ovine ostertagiosis in a graph

Answer 14

Build up of L3s from July –> October from :

• eggs passed by ewes (peripaturient rise) - most important
• eggs passed by lambs from 1st generation parasites established from overwintered larvae

Development of eggs to L3 in warmer months –> speed up development

Lamb begin to graze in April/May

Major difference in b/w sheep and cattle is that egg output of ewes in important and they also need deworming, but resitance is a major concern

Best control is not grazing on heavily infested pasture in summer

Question 15

Hemonchus species in sheep

Answer 15

H. contortus = barber’s pole

H. similis = mainly cattle

Question 16

Hemonchus contortus - basics and lifecycle

Answer 16

• Largest parasite in abomasum, sucks blood –> anemia
• Barbers pole
• Very pathogenic (poor immunity)
• Very important in tropical climates
• Sporadic dz in temperate climates
• Anthelmentic resistance

Life cycle

• egg –> L1 to L3 in pasture –> ingestion, typical trichostrongylid

can go from egg to L3 in 5-7days

Ewes remain susceptible to dz