Rev: 10/20/2025
Chromadorea
Chromadoria
Rhabditina
Synonyms:
Strongylus filicollis Rudolphi, 1802
Like nematode genera of many families in the Infraorder Rhabditomorpha, the species of Nematodirus are usually identified on characteristics of the male bursa and spicule tips. Identification of females has been very difficult, but the synlophe pattern is provng to be a useful tool. The synlophe, the system of longitudinal cuticular ridges on nematodes of the Trichstrongyloidea, provides an important diagnotstic aid. It is also useful in other superfamilies, including the Molineoidea.
In the Molinidae, most species have synlophes with variations of an 18-ridge bilaterally symmetrical system in the cervical region. A sixth species has 26 cervical ridges. Two groups of species of genus Nematodirus are recognized on the basis of synlophe characteristics and other morphological features:
Group 1. Nematodirus filicollis and N. davtiani have reductions in lateral ridges in the postcervical region so that there are 14 ridges at.midbody. The two species also have finlike ridges, a small number (30-35) of perioral denticles, a short cephalic expansion, and a large bursa without a separate dorsal lobe.
Group 2: Nematodirus helvetianus, N. oiratianus interruptus, N. abnormalis, and N. spathiger have a more posteriorly distributed pattern of ridges in the cervical region, 18 or more ridges nearm id-body, smaller dorsal and ventral ridges, a larger number (50-65) of perioral denticles, a longer cephalic expansion, and a smaller bursa with separate dorsal lobes. Nematodirus oiratianus oiratianus have continuous ridges. Nematodirus spathiger and N. abnormalis have 18 ridges for most of their length; they lose all dorsal ridges and add a few ventral ridges in the last quarter of the males
Ref: Lichtenfels and Pilitt, 1983; 2000).
Synlophe patterns of Nematodirus spp. of NortheAmerican domesticated ruminants with positions of cervical papillae (cp, excretory pore (exp) and end of esophagus (es). from left to right: N. filicollis, N. davtiani, N. helvetianus, N. oiratianus interuptus, N. abnormalis, N. spathiger.
Drawings from Lichtenfels and Pillit, 1983
General Characteristics:
Slender, body lengths vary with species, up to about 25 mm long.
Cuticle with about 18 longitudinal striations.
Mouth opening circular with a serrated, denticulate, circularized crown and a triangular dorsal tooth
Females:
Uterus contains large ovoid, colorless eggs (twice the size of typical trichostrongyle eggs)
Tail truncated tail with a small spine.
Ref: Snyder et al., 2020
Males:
Worldwide, most commonly in temperate zones (Snyder et al., 2020)
Food Sources and Feeding strategies for the genus Nematodirus
Intestinal parasites of sheep, goats, cattle, antelope and other ruminants.
Nematodirus species has a lifecycle with a unique preparasitic phase; the infective L3 develops within the eggshell. The infective L3 hatches depending on environmental stimuli, which varies by species.
Life history patterns are relatively similar among trichostrongylines, including those of Molinoidea. Infections and develpoment of parasitic larvae are usually limited to the lumen or mucosa of the gastrointestinal system.
Life-cycle simple and direct without the need for an intermediate host. Infective third-stage larvae develop within the egg. The prepatent period is generally about 21 days (Van Dijk and Thomas, 2008; Snyder et al., 2020).
Treatment of infected ruminants with benzimidazole anthelminthics. In New Zealand, following repeated treatments with albendazole, Nematodirus spathiger exhibited a high level of resistance to albedazole treatement. Resistance to treatement also occurred in N. filicollis, but was less frequent.
Lichtenfels, J.R and Pilitt, P.A. 1983. Cuticular Ridge Patterns of Nematodirus (Nematoda: Trichostr richostrongyloidea) P ongyloidea) Parasitic in Domestic Ruminants of Nor asitic in Domestic Ruminants of North America, with a Key to Species. Poc. Helminthol. Soc. Wash. 50:261-274
Lichtenfels, J.R and Pilitt, P.A. 2000. Synlophe Patterns of the Haemonchinae of Ruminants (Nematoda: Trichostrongyloidea). Journal of Parasitology, 86:1093-1098.
Olover, A.M.B., Pomroy, W.E., Leathwick, D.M. 2016. Benzimidazole resistance in Nematodirus spathiger and N. filicollis in New Zealand. New Zealand Veterinary Journal 64:201-206.
Snyder, D.E., Marchiondo, A.A. Cruthers, L.R. 2020. Nematoda, Trichostrongyloidea. Chapter 2 in Marchiondo, Cruthers and Fourie (eds) Parasiticide Screening Vol 2. Academic Press
Van Dijk, J. and Morgan, E.R. 2008. The influence of temperature on the development, hatching and survival of Nematodirus battus larvae. Parasitology 135:269-283.