Small Brown Stomach Worm (Ostertagia ostergi)

The small brown stomach worm (Ostertagia ostertagi) is the most production-limiting parasite for young cattle in cooler, higher rainfall regions. This includes temperate, winter rainfall and non-seasonal rainfall districts across Australia.

The worms themselves are 8-12mm in length and live in the fourth stomach (abomasum) of cattle and can mature into reproductive adults within 3 weeks. Once they’re adults, females can lay 50-100 eggs per day.

Small Brown Stomach worms damage gastric glands in the abomasum and reduce your cattle’s ability to absorb nutrients, resulting in low feed conversion and growth rates. Small Brown Stomach worm causes two main forms of disease, known as Type 1 and Type 2 Ostertagiosis, both inducing significant implications for animal productivity and health.

Brown Stomach Worm Life Cycle

Worm eggs are excreted in cattle faeces.
Worm eggs hatch in cattle dung pats when climatic conditions suit; within 4 to 12 days in the summer, or 5 to 10 weeks in the winter.
Larvae mature to an infective larval stage (L1 to L3) in the dung-pats.
Infective larvae migrate onto the pasture and are ingested by grazing cattle.
Consumed larvae can develop into adult worms in the abomasum within 3 weeks OR Consumed larvae encyst (go dormant) in the stomach wall and remain dormant/inhibited until environmental conditions become favourable again (hypobiosis).

Signs of Brown Stomach Worm Infection

Small Brown Stomach worm damages gastric glands and reduces the animal’s ability to perform chemical digestion to be able to absorb nutrients from food. While it is the cattle worm with the most clinical cases, most cattle develop immunity to Ostertagia by 2 years of age.

Clinical signs of Small Brown Stomach worm infection depends on the type of infection.

Type 1 Ostertagiosis

Type 1 Ostertagiosis occurs when young cattle (up to 18 months) consume large amounts of infective larvae within a short period of time (4-8 weeks) in the winter and spring. The larvae develop into adults in 3 to 4 weeks and damage the structure and function of the abomasum lining. This results in scouring, reduced growth rates & loss of weight. Most of the mob will be affected but generally respond positively to drenching.

Signs of Type 1 Ostertagiosis
- Scouring
- Decreased growth rates
- Weight loss & ill thrift

Type 2 Ostertagiosis

Type 2 Ostertagiosis occurs when thousands of dormant/inhibited larvae simultaneously complete their development and emerge out of the stomach wall, causing severe damage to the stomach, resulting in diarrhoea, weight loss and ill-thrift. This destroys the stomach lining, affecting stomach acid production, digestive enzymes and mucus. This presents as extreme weight loss, poor digestion, scours, decreased feed intake and death. Usually only a few animals are affected at one given time. Cases of Type 2 Ostertagiosis typically occur in late summer and early autumn, when pastures are dry and worms are not the suspected cause.

Signs of Type 2 Ostertagiosis
- Rapid loss of condition
- Intense scouring
- Death

Treatment and Prevention

For effective treatment of Brown Stomach worm, use drenches at times when they will have the greatest effect on the life cycle. This involves treating cattle with a drench that will target mature and immature forms of Ostertagia, including any of the Vetmec Injections or Vetmec Pour-On. Failing to treat the immature worms that are dormant in the abomasum lining can have catastrophic effects and will not prevent Type 2 Ostertagiosis. Vetmec LEV Pour-On is great at treating the adult worms, but will not kill the dormant ones on its own, and that’s why we recommend using it in conjunction with Vetmec Pour-On, Vetmec Injection, Vetmec F or Vetmec LA.

Ostertagia infections often are hand in hand with burdens of small intestinal worms (Cooperia species) and nodule worm (Oesophagostomum radiatum). Preventing Brown Stomach Worm issues involves limiting contamination of pasture with worm eggs when conditions for development are most favourable (Autumn and Spring). Young cattle are most susceptible to the effects of these worms, so avoid grazing them on highly contaminated paddocks, or on paddocks with a bad worm history. The best way to keep Small Brown Stomach worm in check is to conduct regular worm testing (faecal egg counts), so that infections can be identified and treated before they start to limit production.