The most significant worm of cattle in agricultural areas of Western Australia (WA) during winter is the brown stomach worm (Ostertagia ostertagi). Cattle showing symptoms of brown stomach worm are referred to as being affected by ‘ostertagiosis’.
Other cattle worms present in WA are black scour worm (Trichostrongylus species), the thin-necked intestinal worm (Nematodirus species), hair worm (Cooperia oncophora) and the large bowel worm (Oesophagostomum radiatum).
The blood-sucking barber’s pole worm (Haemonchus placei) is found in the abomasum of cattle and large burdens will result in weakness and sudden death. This parasite is normally found in cattle located in tropical and subtropical areas like the Kimberley region of WA. However, barber’s pole worm has now been detected in some cattle herds located on properties in the temperate southern region of WA. Although barber’s pole worm has been detected, the worm burden was low and was insufficient to cause clinical disease in these cattle.
Drench resistance is now known to be present in some cattle herds in WA. A recent study found the hair worm (Cooperia oncophora) was resistant to ivermectin (macrocyclic lactones or ML group) in two-thirds of tested herds. However, the benzimidazole (white) drenches and levamisole (clear) drenches were fully effective against hair worm in these herds.
Most importantly, ivermectin was still fully effective against the brown stomach worm (most significant cattle worm) in the tested herds. However, the brown stomach worm was resistant to the white and clear drenches in half of the tested herds. With resistance now detected in two cattle worm species to two different chemical groups, the use of a combination drench is recommended to ensure effective control of all important cattle worms.
There are four drench groups:
- Combination drenches (for example, Eclipse® or Trifecta®) should be fully effective against all worms in cattle herds including those where drench resistance has developed. This drench group contains an ML as well as one or two other drench components. It is the preferred drench when treating yearling cattle at weaning to reduce the chance of survival of any resistant cattle worms.
- Macrocyclic lactones or single ML drenches e.g. doramectin, abamectin (Avomec®), ivermectin (Ivomec®, Ivomec® Eprinex®, Bomectin®), and moxidectin (Cydectin®, Cydectin® Long Acting) - injectable and pour-on formulations. This group will also control sucking lice and ticks. The single ML group of drenches can be used in cattle herds where the brown stomach worm is not suspected or known to have resistance to this drench group. The ML drenches kill the larval stages of the brown stomach worm which is very important to minimise future burdens of this parasite during winter. Residues of some of the ML drenches in cattle dung may have a harmful effect on dung beetles.
- Bezimidazoles or white drenches (for example, WSD Fenbendazole Oral®, 4Farmers Fenbendazole Oral®, Fencare®, Panacur®, Systamex®) - oral drench and rumen injection formulations. Brown stomach worm resistance to white drenches has been demonstrated on 50% of tested cattle herds in WA.
- Levamisole or clear drenches (for example, Levamisole Gold LV®, Coopers Nilverm oral or pour on®, WSD levamisole®) - oral drench, injectable and pour-on formulations. Brown stomach worm resistance to clear drenches was detected on 50% of tested herds in WA.
Note: Mention of trade names does not imply endorsement or preference of any company’s product by the Department of Primary Industries and Regional Development and any omission of a trade name is unintentional. Recommendations are current at the time of publishing.
There is always the potential for worms to cause reduced weight gain in yearling cattle during winter even if signs of worm disease are not seen. Consequently, treating yearling cattle with an effective drench in autumn is a worthwhile consideration especially in medium and high rainfall areas.
Beef calves rarely suffer from worm parasitism before weaning and routine treatment is not usually warranted.
Drench at weaning with a combination (preferred) or a single ML drench (check your worm drench resistance status). The use of white or clear drenches without a ML component is not recommended in WA. If there has been a history of possible worm problems during winter on the property then an additional preventative treatment in autumn with a combination or single ML drench may be useful.
Two-year-olds/first calf heifers
Young adults are potentially more susceptible to the effects of worms during winter compared with mature adult cows. A preventative autumn drench to young adults may be warranted if you have a history of worm problems in your herd.
Mature adult cows
Most mature adult cows have only minor worm burdens due to strong immunity against worms and do not require a routine drench. However, individual mature adult cows during winter can develop signs of worm disease and these individuals should be treated with an effective drench.
Bulls are more at risk from the effects of worms compared to mature adult cows and a preventative autumn drench before joining is a good precautionary measure.
Ostertagiosis Type 2
A different form of worm disease, ‘ostertagiosis Type 2’, can cause severe effects on cattle but is now a relatively rare occurance in WA. It occurs when there is a mass emergence of larval stages of Ostertagia (brown stomach worm) from the gut wall. This causes severe damage to the gut, and is seen as profuse scouring, rapid dehydration and death if not treated. It manifests mostly in adult cattle, more so in bulls, from late summer to early winter.
Contact a vet sooner rather than later to confirm the diagnosis and discuss a treatment and prevention of the disease.
If there is no response following a drench treatment in cattle and the scouring persists and affected animals continue to lose condition ask your veterinarian to investigate. The cause may not be what you think.
The Subsidised Disease Investigation Program, delivered by the Department of Primary Industries and Regional Development (DPIRD), provides subsidised veterinary investigations (subject to approval by the local DPIRD Veterinary Officer) for livestock diseases with high stock losses or which have similar disease signs to an exotic or reportable disease. Call a private or DPIRD veterinarian, or the Emergency Animal Disease hotline 1800 675 888 after hours.
All livestock disease investigations provide evidence of the internationally high health status of WA and Australia, supporting the export of Australian livestock and livestock products around the world.