This parasite is mostly a problem in dairy calves, 4-12 months of age and reared in the summer rainfall regions of coastal and subcoastal Australia.
Disease occurs where heavy overstocking on permanently moist pastures occurs, or in calves managed on wet muddy yards or crowded onto boggy areas around water troughs or other watering points. Young cattle quickly develop a strong resistance to infection by about 12 months.
Hookworm is a stout worm 10-28 mm long with a large mouth and a body that may appear to be hook-shaped. It feeds on blood and usually occurs in mixed infections with barber’s pole worm (Haemonchus placei), nodule worm (Oesophagostomum radiatum) and small intestinal worms (Cooperia species).
Modern anthelmintics have reduced the incidence of this parasite.
Further ecological information on worms and their control:
Figure 1. Hookworm Bunostomum spp, showing mouth. Image courtesy of Lindsay Jue Sue and Constantin Constantinoiu
Hookworm occurs in the duodenum and anterior part of the small intestine.
The main clinical sign is anaemia as this worms feeds on blood. Anaemia may be exacerbated by concurrent infections with barber’s pole worm (Haemonchus placei) and liver fluke. Hookworms may also cause weakness and loss of appetite, a black diarrhoea, a sub-mandibular oedema ‘bottle jaw’, and typically, sore feet from infection at the site of larval entry.
The only accurate way to confirm worm infections before productivity losses have occurred is to conduct a worm egg count (WEC). Clinical signs often occur at low egg counts. A larval culture or DNA test is important to confirm the presence of hookworm along with other pathogenic worms, such as barber’s pole worm (Haemonchus placei) and small intestinal worm (Cooperia species).
However, when clinical signs are caused by the immature or pre-adult stages, ‘diagnostic’ drenching (drenching when worm egg counts are low but there is a history of favourable conditions and suggestive clinical signs) using a fully-effective drench can be a useful tool. Visual responses to the drench in terms of improved condition and weight gains are suggestive of a parasitic infection.
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.
Figure 2. Hookworm in the small intestine feeding on blood. Image courtesy of the National Centre for Veterinary Parasitology, ncvetp.org
There are many options to treat for this worm and your choice of drench and management options will depend on:
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.