Nematodirus leporis



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N. leporis is a thin-necked intestinal worm that is occasionally found in wild rabbits and hares. Pet-rabbits that live in temperate, cold, and elevated environments can also be infested. N. neomexicanus, N. arizonensis and N. triangularis have furthermore been reported in wild rabbits. There is no reported public health danger related to this parasite.

The life cycle of Nematodirus leporis is direct, with no intermediate host. The thick-layered eggs are much larger (250*100 mm - micrometer) than those from other Trichostrongylidae and are extremely resistant to desiccation and to freezing conditions or snow. Usually the eggs have started to divide rapidly and 1 to 8 dark cells can be observed. The development of the larvae is generally slow, up to 2 months in temperate climates. It is dependent on the humidity and the temperature of the environment. During hatching, the larva shed the first-stage-cuticle, which is left behind in the egg-shell. The L3 larva remains within in the egg- shell, which provides protection against adverse environmental conditions. The L3 larvae can thus survive up to one year in pasture fields. Once the L3 larva is ingested by the host, it will exsheath and move to the paramucosal lumen of the small intestine, and molt into the L4 and immature adults.


Egg of Nematodirus sp.

The adult parasite is slender and measures 30 mm long. Its body shape is curled and presents 18 longitudinal striations. The anterior part is reduced, with an inflated cuticle, which is usually striated. The anterior part is inflated with a noticeable dorsal esophageal spicule. The male worms possess a bursa with 2 large lateral lobes, covered with mediolateral and caudolateral striations. The female has a tale that ends bluntly.


Nematodirus leporis: head and spicule

Clinical signs

The clinical and pathological sign of the presence of Nematodirus sp. only becomes noticeable with a severe infestation, leading to diarrhea, a loss of weight and affected performance. Necropsy shows that the large numbers of worms form clumps resembling cotton wool, and are usually intertwined around the intestinal villi, causing atrophy, degeneration and necrosis of the surface enterocytes.

The occurrence of Nematodirus sp. is analyzed by fecal flotation, for the presence of the particularly large Strongyle-type eggs.




20 mg/kg, PO, repeated after 10-14 days



0.4 mg/kg, SC, repeated after 10-14 days

Further Information

Audebert F, Cassone J, Kerboeuf D, Durette-Desset MC. The life cycle of Nematodiroides zembrae (Nematoda, Trichostrongylina) in the rabbit. J Parasitol. 2002; 88(5):898-904.

Hoste H, Mallet S, Fort G. Histopathology of the small intestinal mucosa in Nematodirus spathiger infection in rabbits. J Helminthol. 1993; 67(2):139-44.

Hoste H, Fort G. Experimental infections with Nematodirus spathiger in rabbits. J Helminthol. 1992; 66(3):227-30.

Andrews CL, Davidson WR. Endoparasites of selected populations of cottontail rabbits (Sylvilagus floridanus) in the southeastern United States. J Wildl Dis. 1980; 16(3):395-401.

Knight RA. Effect of dexamethasone on experimental infections of Trichostrongylus affinis and Nematodirus spathiger in rabbits. J Parasitol. 1977; 63(5):957-8.

Jansen J. Where does Nematodirus battus Crofton & Thomas, 1951, come from? Vet Rec. 1973; 92(26):697-8.

Gallie GJ. The pathogenicity of Nematodirus battus in weaned and unweaned laboratory rabbits. J Helminthol. 1973; 47(4):377-88.

Gallie GJ. The development of acquired resistance and age resistance to Nematodirus battus in the laboratory rabbit. J Helminthol. 1973; 47(4):369-76.

Mapes CJ. Bile and bile salts and exsheathment of the intestinal nematodes Trichostrongylus colubriformis and Nematodirus battus. Int J Parasitol. 1972; 2(4):433-8.

Gallie GJ. Development of the parasitic stages of Nematodirus battus in the laboratory rabbit. Parasitology. 1972; 64(2):293-304.