Cooperia oncophora

Cooperia oncophora
L3 stage larva of C. oncophora. Courtesy of Russell Avramenko.
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Chromadorea
Order:	Rhabditida
Family:	Cooperiidae
Genus:	Cooperia
Species:	C. oncophora
Binomial name
Cooperia oncophora

Cooperia oncophora is one of the most common intestinal parasitic nematodes in cattle in temperate regions. Infections with C. oncophora may result in mild clinical symptoms, but can lead to weight loss and damage of the small intestine, especially when co-infections with other nematodes such as O. ostertagi occur. Infections are usually treated with broad-spectrum anthelmintics such as benzimidazole, but resistance to these drugs has developed in the last decades and is now very common.C. oncophora has a direct life cycle. Infective larvae are ingested by the host. The larvae grow to adults, which reproduce in the small intestines. Eggs are shed onto the pasture with the faeces, which leads to new infections. Co-infections with other gastro-intestinal nematodes such as O. ostertagi and H. contortus are common.

C. oncophora females are about 6–8 mm long, males about 5.5–9 mm. They are light red in color and have a coiled shape. Male worms have a large bursa as shown in Figure 2a. The spicules are 240-300 µm long and have a rounded end and a longitudinal line pattern. L3 stage larvae are hard to differentiate between different species, because they are very similar interspecies-wise. Eggs of C. oncophora however can be easily identified by their parallel walls.

The life cycle of C. oncophora is direct. Free-living L3 stage larvae residing on the pasture are taken up by grazing cattle and pass to the small intestine. Here, they molt to L4 larvae and then to adults. Eggs are passed in the faeces to the pasture. The larvae hatch and grow to L3 stage larvae. Infective L3 stage larvae are then again taken up by grazing cattle and the life cycle repeats. The pre-patent period, which includes the time between infection and egg laying, lasts between two and three weeks. Like other trichostrongylids, early C. oncophora L4 larvae are able to arrest their development under unfavourable environmental conditions such as low temperatures and high dryness, a process termed hypobiosis. L4 larvae can stay arrested up to five months.

...
Wikipedia