Microscopic males and females live freely in the soil.
The female lays only a few eggs that contain a developed embryo.
(It is believed by some that the free living female only lays one generation of eggs)
The egg hatches into first stage larvae shortly after laying.
The first stage larvae molts into the second and third stage then into the free-living
male or female adult worms within 48 hours after the egg hatches.
The third stage larvae of the free-living form have a rhabditiform type of esophagus.
However, if the environment becomes unfavorable, the second stage larva molts into
a different type of third stage larvae.
This infective larva needs to find a host to continue its development.
The third stage parasitic larvae have a filariform type of esophagus.
This infective third stage usually infects the goat and other ruminants by
penetrating the skin usually around the feet.
The larvae travel through the blood to the heart and then to the lungs.
The larvae molt in the trachea where they are coughed up and swallowed.
After passing through the stomachs, the larvae molt again and penetrate into
the mucous membrane of the small intestine.
The adult parasitic form exists only as females.
Males are unknown.
The females lay eggs just 5 to 7 days after infection.
The parasitic female is long and slender with a very long esophagus.
The embryonated eggs leave with the feces.
After hatching the larvae can develop into either more infective parasitic larvae
or into the free-living male and female adults.
The parasitic larvae can also be swallowed on contaminated food.
The larvae molt in the intestine, penetrate the intestinal mucosa and continue
to the adult parasitic female.
Oocyte: 40-60 µm long by 20-25 µm wide. Embryo is developed when passed with feces.
Heavy exposure can cause coughing, diarrhea, loss of weight and mild anemia
due to erosion of intestinal mucosa.
Larvae can introduce foot rot organisms into skin around hoof due to irritation from burrowing.
Adult animals develop immunity to re-infection.