Nodule worm

(Oesophagostomum radiatum)

Oesophagostomum radiatum is found throughout Australia, but especially prevalent in tropical and sub-tropical areas, usually in mixed infections with barber’s pole worm (Haemonchus placei) and small intestinal worms (Cooperia species). It is also common along the eastern coast of Australia in young beef cattle 4-12 months of age, and young dairy cattle 5-8 months of age, and across northern Australia.

The nodule worm is a large (14-22 mm long) white stout worm with the adult female laying 5,000–12,000 eggs per day. Worms erode the walls of the small and large intestine during feeding leaving lesions, 3-6 mm in diameter scattered along the serosal (lining) surfaces of the intestines.

Broad-spectrum drenches tend to keep nodule worms at low levels and are effective against the stages in the wall of the intestines. Larvae migrating through the walls can become trapped and the lesions that form around them are small and gritty in the small intestine and larger and caseous in the large intestine.

Further ecological information on worms and their control:

  • Roundworm life cycle and life stages
  • Nodule worms have a typical roundworm life cycle except that the exsheathed infective (L3) larvae in the small intestine undergo an inhibited tissue phase resulting in nodule formation. In a primary infection, fourth (pre-adult) stage larvae migrate from the intestinal wall and into the caecum and colon to resume development into adults in the large intestine. In subsequent infections, host immunity delays migration out of the intestinal wall. Parasites may live for up to 8 months or longer in some animals. The pre-patent period is 32-42 days. Infective larvae on pastures are very susceptible to cold and dryness and may only survive a few weeks on pastures.
  • Climate factors contributing to paddock contamination with worms
  • Pasture management to reduce exposure to worms
  • Cost of roundworms

Location in host

Adult nodule worms are found in thick mucus in the caecum and proximal colon.

 

Figure 1. Nodule worm, Oesophagostomum sp. Image courtesy of Mukund Madhav

Figure 2. Anterior end of a nodule worm, Oesophagostomum radiata. Image courtesy of Constantin Constantinoiu

Signs

Nodule worms cause severe anorexia and wasting, a marked and persistent green mucoid diarrhoea (scouring) with a nauseating odour, also anaemia and ‘bottle jaw’. Badly affected stock may walk with a stiff stilted gait especially of the hind limbs and have a humped back from abdominal pain. In the severe form of the disease, death usually occurs 2 to 3 months after the onset of clinical signs.

Signs of worms

Diagnosis

The only accurate way to confirm worm infections before productivity losses have occurred is to conduct a worm egg count (WEC).

Clinical signs occur at very low egg counts. For stock in hot summer rainfall regions a larval culture or DNA test is important to identify if nodule worm is present along with other pathogenic worms, such barber’s pole (Haemonchus placei) and small intestinal worms (Cooperia species).

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.

The results of the worm egg count allow you to make the best choice of drench treatment for the situation. 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.

Nodule worm can be diagnosed during post mortem examination when nodules and the worms are clearly visible. In severe infestations, the intestinal tract from the duodenum posteriorly is studded with innumerable dark bluish-green nodules in the submucosa with excessive amounts of turbid mucous.

Treatment

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.