Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Nematodirus spathiger (sheep)

Category:


Species:
Endoparasite


Description:
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Nematode (order Strongylida)

"thread-neeked strongyle"

Distribution: 
Nematodirus spathiger - worldwide. Nematodirus fillicollis and Nematodirus abnormalis - worldwide, except Africa. Nematodirus battus - Scotland, England.

Host: For many years Nematodirus was not considered to be pathogenic, but experimental evidence indicates otherwise. For instance, Nematodirus battus causes significant mortality in lambs in Britain.

Life Cycle: Direct life cycle in small intestine. Infective larvae develop within the eggshell on pasture. Larvae within egg shells are very resistant to drying and freezing and may thus survive winter weather to infect sheep in early spring or late winter. Nematodirus battus and N. fillicollis, in fact, require prolonged exposure to cold temperatures before they are able to hatch. Infection is by ingestion of third-stage larvae, free-living or in eggs. The prepatent period ranges from 15 to 28 days. 

Diagnosis: 
Characteristic large strongyle-type eggs appear in feces. Relatively long, thin nematodes, from 10 to 30 mm. in length, with a thin anterior portion that enlarges at the front end of the worm, giving the head region a swelled appearance. 

Size: 150 µm x 75 µm, poles sharply curved, shell thin, colourless, 2-8 blastomeres  Nematodirus fillicollis egg

Clinical features:  
Larval stages are the primary cause of disease. The lining of the small intestine is greatly damaged; pieces of it may become loose and be shed in feces. Loss of appetite, diarrhea, and weight loss may occur. Wool growth is reduced in chronic infections. The overwintering of infective Nematodirus battus larvae in Great Britain provides larvae for infection in the spring. Lambs on such pasture receive great numbers of larvae in a short period of time. Acute diarrhoea and dehydration result; 10 percent of the lambs may die.
 
Control:
Pasture management and regular anthelmintic treatments of infected sheep should be employed to reduce parasite loads.


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