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The long-necked bankrupt worm – or thin-necked or thread-necked worm – belongs to the genus Nematodirus and is found worldwide. These roundworms are internal parasites that infect the small intestines of sheep, goats and cattle. Infection with this type of worm is known as nematodirosis.
The long-necked bankrupt worm is different from other common roundworms as it is prominent in winter, which is not suitable for the development or survival of roundworms.
Read more about effective worm control.
Life cycle of the worm
Adult female worms lay their eggs in the small intestine of the host. The eggs are shed through the faeces where the larvae of Nematodirus spp. undergo complete development inside the shell of the egg.
Eggs can survive for one to two years on pasture, only hatching when conditions are favourable. When night and day temperatures average 10°C for more than a week, the larvae will hatch, resulting in a significant larvae load on pasture. When livestock graze on contaminated pasture, they become infected with the worm larvae. Indigested larvae travel to the small intestine of the host where it develops into an adult that can produce eggs.
Clinical signs
Infected adult animals can present with minimal clinical signs and symptoms, but problems do occur with newly weaned grazing lambs and calves. The larval stage is the most dangerous because they feed on the wall of the gut, severely damaging it. Signs of nematodirosis in livestock include diarrhoea and dehydration, caused by faulty digestion and absorption of nutrients due to the damaged wall of the gut.
Parasitic gastroenteritis (PGE) is an infection caused by gastrointestinal parasites such as the long-necked bankrupt worm. Clinical signs of PGE are ill-thrift, diarrhoea, weight loss and, when accompanied by other roundworms, anaemia, and peripheral oedema. If infected livestock are not treated, 10% or more can die even when larvae did not reach adulthood inside the host.
Infection with this parasite can be diagnosed based on the clinical signs and symptoms, but the most accurate way to diagnose infection is to conduct a worm egg count and egg identification. With lambs it is difficult as they can become seriously ill without eggs present in their faeces, due to larvae not developing into adults.
Nematodirus spp. has a devastating impact on young livestock. When cattle present with observable signs of nematodirosis, serious production loss has already occurred. When lambs recover from nematodirosis with anthelmintic therapy, it will result in a slower growth rate, leading to a longer period for the lamb to reach market weight, further contributing to financial losses.
Control and prevention
When considering methods to control this roundworm, it is important to remember that reinfection occurs when livestock is reintroduced to infected pastures when foraging. Keeping animals in a dry pen will decrease their chances of reinfection, thereby interrupting the life cycle of these parasites.
Another method that will prevent nematodirosis is by adopting rotational grazing policies. Rotational grazing entails land that is divided into smaller paddocks, with livestock moved from on paddock to another. Removal of manure will also decrease the risk of infection.
The control methods mentioned would benefit from the appropriate anthelmintic drugs, especially in terms of strategic administration of benzimidazole compounds, as it is safe to use on young livestock. Anthelmintic treatment can be seen as inexpensive whereas drenching can be more time consuming, especially when tending to a large group of young lambs.
To decrease nematode resistance in your livestock, it is important to use products containing different active ingredients of different chemical classes as advised by your veterinarian. To ensure that your livestock remain protected against new roundworm infections, animals must be dewormed regularly. – Clearly Simpson
For enquiries or a list of references, email the author at simpsonvicleary@gmail.com.
