Table 1 Morphological characteristics, pre-patent periods and locations in the host of key genera and species of gastrointestinal nematodes infecting sheep in Australia[6, 7, 10, 11]

Trichostrongylidae

Haemonchus contortus

♂ 10-20

Red pseudocoelomic fluid and white coiled ovaries giving the appearance of a barber's pole.

18-21

Abomasum

♀ 18-30

Presence of vulvar flap depends on strain.

Teladorsagia circumcincta

♂ 7-8

Small head and buccal cavity.

15-21

Abomasum

♀ 10-12

In females, a vulvar flap can be present.

Trichostrongylus axei

♂ 2-6

Dissimilar spicules of unequal length.

15-23

Abomasum

♀ 3-8

or stomach

T. colubriformis

♂ 4-8

Equal length spicules with triangular tip.

15-23

Anterior small intestine

♀ 5-9

T. vitrinus

♂ 4-7

Equal length spicules with sharp tips.

15-23

Anterior small intestine

♀ 5-8

T. rugatus

♂ 4-7

Dissimilar spicules with foot-like appearance.

15-23

Small intestine

♀ 6-7

Cooperia curticei

♂ 4-5

Transverse striation of cuticle in all species.

14-15

Small intestine

♀ 5-6

Watch-spring-like body posture and presence

a small cephalic vesicle are characteristic.

Molineidae

Nematodirus spathiger

♂ 10-19

Small but distinct cephalic vesicle.

18

Small intestine

♀ 15-29

Very long spicules ending in a

spoon-shaped terminal piece.

N. filicollis

♂ 10-15

Small but distinct cephalic vesicle.

18

Small intestine

♀ 15-20

Long and slender spicules with a

narrow, lanceolate membrane.

Ancylostomatidae

Bunostomum trigonocephalum

♂ 12-17

Anterior end is bend dorsally,

40-70

Small intestine

♀ 19-26

Buccal capsule with two cutting plates.

Chabertiidae

Oesophagostomum columbianum

♂ 12-16

Have two leaf crowns and a shallow

40-45

Large Intestine

♀ 14-18

buccal capsule. Position of cervical papillae

used for species differentiation.

O. venulosum

♂ 11-16

Cervical papillae are situated

40-45

Large intestine

♀ 13-24

posterior to the oesophagus.

Chabertia ovina

♂ 13-14

Mouth is directed antero-ventrally.

42-50

Large intestine

♀ 17-20

Buccal capsule is subglobular

without teeth.