Goat Parasite Life Cycle Animations

Nematodirus spathiger

Thin-necked intestinal worm

The thin-necked intestinal worm lives in the small intestine.
Female worms are not heavy egg layers, so few eggs may appear in the fecal count
even if there are heavy loads of adults in the intestine.

The large eggs passed with the feces are in the early stages of development.


The larvae molt to the third stage inside the egg.
This is a slow process even at optimal temperatures 77 - 86F (25-30C).
The unhatched larvae can survive almost 2 years in dry conditions and are resistant to freezing.


In humid conditions and temperatures over 75 F (25C), the larvae hatch out in about 2 weeks.
After hatching, infective larvae crawl up moist blades of grass.


The goat becomes infected by swallowing the larvae or eggs containing infective larvae.


The larvae migrate to the small intestine where they suck blood.
In about 3 to 4 weeks the adult stage is reached and the female begins to lay eggs.

Red colored adults have a coiled thread-like head end.
Males 10 - 15 mm long, females 15 - 23 mm long.

Clinical Signs

Since infective larvae overwinter on the pasture heavy infections can occur in the early spring.

A young goat may have diarrhea and loss of appetite if infected with large numbers of this parasite,
but infections of this parasite alone generally do not cause ill health.
Mixed infections with other stomach and intestinal worms often occur.

Oocyte: large (175 - 260 µm long X 110 µm wide)
in early four to eight-cell stage of development