Small intestinal worms

(Cooperia oncophora, C. pectinata, C. punctata)

Cooperia punctata, C. pectinata and C. oncophora are the most commonly found small intestinal worms of cattle of all ages. They are small worms 5-9 mm long, and very hard to see with the naked eye.

Cooperia punctata and to a lesser extent C. pectinata, are the major species in northern warm regions with predominantly summer rainfall and often cause severe enteritis in calves when in large numbers. Recent research indicates the range of these two species is extending south with both species now regularly recovered from larval cultures in southern Australia.

By contrast, C. oncophora is distributed in more temperate regions with wet winters, where it is often the most prevalent worm in larval cultures. This species can affect weight gain, especially in younger animals. Cooperia may contribute to the severity of disease in mixed parasite infections.

Cattle generally develop a strong immunity to reinfection by 12 months.

Figure 1. The L3 larval stage of a small intestinal worm, Cooperia oncophora. Image courtesy of Russel Avramenko Wikimedia commons

Resistance in all Cooperia to the macrocyclic lactone drenches has been reported.

Further ecological information on worms and their control:

  • Roundworm life cycle and life stages
  • Small intestinal worms have a typical roundworm life cycle, except up to 50% of early fourth (L4) pre-adult stage infective larvae can be halted during periods of high larval intake. Under ideal environmental conditions, development from egg to third stage larvae(L3) in the dung pat takes around seven days, but can be as long as five weeks. The pre-patent period for C. punctata is 11-16 days, and 17 -22 days for C. oncophora
  • Climate factors contributing to paddock contamination with worms
  • Pasture management to reduce exposure to worms
  • Cost of roundworms

Location in cattle

Small intestinal worms are found coiled along the wall of the small intestine.


Cooperia oncophora affects weight gain, while C. punctata (and C. pectinata) may cause severe disease including diarrhoea, weight loss, inanition (exhaustion) and death, especially in young calves.

Clinical symptoms from infections with up to 30,000 worms consist of a loss of appetite, a listless appearance, and intermittent profuse watery diarrhoea, rapid loss of weight, emaciation, and death.

Signs of worms

Figure 2. Section of a cleared preparation of an adult Cooperia spp showing part of the gut and uterus. Image courtesy of the National Centre for Veterinary Parasitology,


The only accurate way to confirm worm infections in cattle up to the age of 12 months, and before productivity losses have occurred, is to conduct a worm egg count (WEC). As small intestinal worm eggs are typically ‘strongyle type’, also request a larval culture or DNA test. The results allow you to determine the need for a drench or management action.

Worm egg counting does not always correlate well with the number of adult worms present for cattle over 9 months of age. For this age group observation of physical signs such as body condition scoring and monitoring target growth weights are good additional indicators to diagnose worm infections.

If visual signs of worms are present in cattle then significant production loss has already occurred. Also, these signs can occur with other parasites and diseases.


There are many options to treat for this worm and your choice of drench and management options will depend on:

  • The current size of the burden of this worm.
  • What other worms are also present and in what proportion?
  • Which drenches are effective on your property and the length of protection you are seeking?
  • The likely worm-risk over the next few months.
  • The likely level of worm contamination on your pastures.
  • The class of stock affected and their susceptibility to worms.
  • The last drench group/s you used on this (and other) groups of cattle.
  • The time until these cattle are sold/slaughtered and the withholding period and export slaughter interval of drenches you might use.
  • If these cattle are producing milk for human consumption.

Your decision can be assisted by using the how to decide which animals to treat section and the WormBoss cattle products search guide for your region, a simple tool that considers some of the points above. It is also important to consider cattle management options, as simply removing the affected mob to a less wormy pasture will reduce the re-infection risk.

You can also review the chemical pages on this site to find out specific information about drenches, including their drench active, drench group, how they are administered, which worms they treat, resistance status, safety information and how they work.

The negative impact of this worm can also be reduced through using one of the integrated annual worm control programs that have been specifically developed for different regions across Australia.