Stomach and intestinal worms
A broad range of stomach and intestinal parasites are described in this guide.
The life cycles of these parasites begin when cattle ingest infective-stage larvae with grass. Larvae penetrate the stomach or intestinal wall and mature to adulthood within the host. Adults produce eggs, which infect pastures through manure droppings. Eggs hatch into first-stage larvae and then develop to the third stage. Third-stage larvae migrate onto grass and are consumed by cattle. The duration of this life cycle is from five weeks to more than six months, depending on climate. Larvae survive winter temperatures in manure.
Brown stomach worms
The brown stomach worm, Ostertagia ostertagi, is the most common internal parasite of cattle. When grazing, cattle ingest third-stage larvae. Ingested larvae penetrate the gastric glands of the abomasal mucosa, producing nodules. Upon emerging from the gastrointestinal nodules, young adults severely damage the gastric glands and the digestive process. Affected animals suffer reduced appetite and weight loss.
In Type I infections, eggs begin appearing in the manure 18 to 60 days after larval ingestion. Calves from seven to 15 months of age are primarily affected. Effects are seen early in this period in temperate regions and late in the period in cool regions.
In Type II infections, unusual conditions, possibly climatic or nutritional, cause larvae to hibernate in the gastric glands up to six months. Severe damage can occur when these larvae are suddenly released. Type II infection occurs primarily in 12- to 20-month-old cattle. Effects are seen in late summer to autumn in warm-temperature regions and late winter to early spring in cold-weather regions.
Signs of brown stomach worm damage include diarrhea, poor appetite and weight loss. Edema (bottle jaw) may be seen in severe cases. Death may result from serious infections.
Several species of Cooperia parasites—primarily C. punctata, C. oncophora and C. pectincata—infect the small intestine of cattle. Cooperia is also called the small intestinal worm, and infections are found virtually everywhere cattle are raised. The life cycles of these species are similar to those of stomach worms. The period from ingestion of larvae to appearance of eggs in the feces is from 12 to 15 days.
Cooperia infections can impair weight gain. Heavy infections of C. punctata and C. Pectinata produce profuse diarrhea, loss of appetite and emaciation. The disease produced by C. oncophora is milder.