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Ostertagia in Cattle | AG0071 |
John Larsen, formerly Ballarat and Noel Campbell, Attwood
Updated: February 2007
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The main roundworm of cattle is Ostertagia ostertagi, known commonly as the brown stomach worm. Control of Ostertagia will incidentally control other roundworms of lesser importance such as the small intestinal worm (Cooperia sp). Occasionally, the stomach hairworm (Trichostrongylus. axei) can be the predominant parasite but, more importantly, it is the only roundworm species that infects both sheep and cattle.
Life Cycle
Ostertagia and other roundworms of cattle have a simple direct life cycle, as shown in Figure 1. An important feature of this life cycle is that it consists of two stages; the free-living stage on pasture and parasitic stage in cattle.
Eggs from mature females in the abomasum (fourth stomach) are passed in the dung. These hatch in the dung pat to first-stage larvae (L1). These larvae grow and moult to second-stage larvae (L2). The second-stage larvae continue to feed on bacteria in the dung pat and moult to become third-stage or infective larvae (L3).
The third-stage larvae (L3) cannot feed, because they retain the cuticle ("skin") from the second stage (L2) as a protective sheath, but can survive for long periods within the dung pat. They can also move some distance away from the dung pat. The parasitic stage of the life cycle of Ostertagia begins when a beast ingests L3 larvae.
In the forestomachs the L3 larvae lose their protective sheaths. They then burrow into the glands of the wall of the abomasum. After moulting to become early fourth stage-larvae (L4), development may continue without delay or be interrupted by a period of up to several months. The lining of the abomasum is significantly damaged when the larvae emerge as immature adult worms.
Large numbers of L4 larvae tend to become inhibited in their development if they are ingested during spring and early summer. These can cause a serious type-2 disease when they resume growth and emerge into the abomasum during late summer and early autumn.
If the L4 larvae develop directly, that is if they don't become inhibited, then adult worms appear 3-4 weeks after infection with L3 larvae.
The Disease
There are two types of disease caused by Ostertagia. The signs of each type result from the same damage to the abomasum:
- Type-1 disease usually occurs in calves and young cattle that have high burdens of adult worms in winter and spring. This disease follows rapid infection with large numbers of L3 larvae from heavily contaminated pastures in the autumn and winter after weaning. Dairy calves typically suffer type-1 disease at 5-6 months. Beef cattle are affected at 15-20 months.
- Type-2 disease occurs especially in beef cows calving for the first and second time in the autumn and winter. This coincides with the stress of calving and the emergence of thousands of inhibited L4 larvae from the lining of the fourth stomach. Severe scouring, loss of weight and even death may result. Frequent drenching may be needed just to keep these cattle alive.
Outbreaks of type-2 disease caused by Ostertagia have become less common in beef cattle in recent years compared to the frequent and severe autumn outbreaks seen in the 1970s. The reason for this decline has been the introduction of the second generation benzimidazole (white) and macrocyclic lactone (mectin) drenches, and lower stocking rates of cattle on most properties.
Drenches
Three groups of drenches are available for use in cattle. The products in these groups are shown in Table 1. All are effective against adult worms in the abomasum. They differ in their activity against the developing and inhibited L4 stages of larvae. The mectins are the most effective against L4 larvae, the benzimidazole drenches follow the mectins and the levamisole group is the least effective.
Some of the drenches in Group 1 (benzimidazoles) have lesser and a more variable effect on the immature and inhibited stages of Ostertagia than previously thought.
Where stocking rates for cattle are high or ostertagiasis is a problem, the use of Group 3 rather than drenches from Group 1 is recommended. Beef calves less than 12 weeks old need not be drenched as they won't be significantly infected with worms. Dairy calves only rarely need drenching before 12 weeks of age. Seek veterinary advice.
The route of administration of drenches (oral, injection, or pour-on) may influence the efficacy of the drench. Oral drenches may be rendered less effective if they bypass the rumen and go directly into the abomasum of some animals.
The pour-on formulations of levamisole have also given variable results in adult cattle in winter. The concentration of the drug in these formulations has been increased in response to these findings, but the lack of effect of levamisole on the inhibited larvae of Ostertagia means that levamisole-based drenches are not ideally suited for use in beef cattle over 12 months old.
Drench Resistance
To date some cases of drench resistance in cattle roundworms have been identified in Australia. This is in contrast with our sheep industry where drench resistance is a significant problem on many farms. However, resistance has been increasing at an alarming rate in recent years on beef rearing farms in New Zealand and South America. Resistance in now widespread in these countries and mainly involves resistance in Ostertagia to the white drenches and in the small intestinal worm (Cooperia) to the mectin drenches. Resistance appears to be associated with intensive rearing or frequent drenching in these countries.
The extent of drench resistance in cattle in Australia is unknown. Investigations to determine the level of worm infection and the occurrence of drench resistance are currently being conducted in heifers on dairy farms in Gippsland and on beef calve rearing farms in SE Australia.
Control Programs - Beef Cattle
Integrated control strategies which combine drenching with movement of cattle to lower risk pasture, will maximise the benefits of drenching by reducing reinfection with L3 larvae. It has been demonstrated that alternative grazing with sheep and cattle has beneficial effects for worm control in both species, as they share only one species of worm and this is of intermediate importance.
Lower risk pastures are those that have low numbers of L3 larvae. These are newly sown pastures, hay aftermath, crop stubbles, fodder crops and pastures that were grazed - since the previous autumn break - solely by sheep or adult cattle over four years of age.
The recommended drenching program for autumn calving beef cattle in southern Victoria is:
- January - weaners, first-calf heifers, second calvers and bulls
- March/April - weaners, bulls and first-calf heifers
- July - weaners only (and shift to low-risk paddock).
Note that routine treatment of adult cows after their second calving is not needed. Individual cows in this group may be treated if they are scouring or losing condition because of infection with Ostertagia.
Control Programs - Dairy Cattle
In dairy herds, infections caused by roundworm can be a major disease of weaned calves in their first winter. This is mainly where calves are reared year after year on the same paddock. As a result, L3 larvae can build up to great numbers. In contrast, adult dairy cows are relatively resistant to worms because of their age and previous infection. Ostertagiasis is even less common in adult dairy cattle than in beef cattle, although occasional cases, especially around the time of calving, do occur.
It is debatable whether low levels of infection with worms affect production of milk. Many conflicting studies have been published and it has been generally accepted that the cost of treating dairy cows to control low burdens of worms exceeds the gains of any additional milk production. Some trials conducted over the last 10 years have recorded responses after treatment with mectins of up to 0.5 L of milk per cow per day. In addition, some drenches cannot be used on lactating dairy cattle.
Routine treatment of adult dairy cows is not generally recommended and only the few individual animals that show signs of disease generally need to be drenched. Treatment of dairy cattle at calving or immediately after it may give a small increase in production of milk in herds that are heavily stocked because it is much easier for cattle to pick up L3 larvae from short spring pastures. However, better nutrition of the herd will produce far greater benefits than drenching.
Farmers should concentrate on reducing infection in weaned calves. The same principles concerning lower-risk paddocks apply to dairy cattle and to beef cattle. It is worthwhile rotating paddocks used for calf rearing from year to year, and practising rotational grazing to provide lower-risk paddocks and improved nutrition. Heifers may need drenching at intervals of two to three months from the time of weaning until eight months of age. The exact frequency will depend on the degree of contamination of the pasture. Irrigation assists the movement of infective larvae from the dung pat to the herbage in much the same way as abundant summer rain does. For this reason there can be significant infections in cattle on irrigated pasture in summer as well as in autumn and winter. Dairy bulls should be drenched in January and April.
Monitor Worms and Drench Efficacy
Worm egg counts conducted on dung samples (e.g., Wormtest) are used to indicate the worm burden in young cattle. WECs are less reliable in cattle older than 12 months.
Use WECs to monitor the level of worms and determine if drenching is needed or not.
Measure the effectiveness of drenching by conducting a second Wormtest two weeks after drenching.
Figure 1. Ostertagia life cycle
Table 1. Some Treatments for Roundworms in Cattle
Please see product labels for full claims and restraints.
Chemical Name |
Representative brand names |
Method of application
|
Withholding periods (days)
|
|
ESI2
|
Milk3
|
| Group 1 (Benzimidazole, BZs or white drenches) |
| Albendazole | Valbazen mini-dose cattle, Strategik mini-dose (cattle), Albendazole cattle mini-drench, Nuwhite CC | Oral | 10 | 10 | Do not use3 |
| Fenbendazole | Panacur 100, Fenbendazole 100, Fencare 100 | Oral | 14 | 14 | Nil |
| Oxfendazole | Worma drench, Systemax concentrated drench, Oxfen C, Oxazole – cattle and horses, Parafen LV, Bomatak C,
Bomatak pour-on, Alternate | Oral
Pour - on | | 14 | |
|
| Group 2 (Levamisole, LEV or clear drenches) |
| Levamisole | Nilverm LV
Nilverm Pour-on
Rycozole RV
Levipor, Big-L pour-on, | Oral
Pour-on
Oral
Pour-on | | | |
|
| Group 3 (Macrocyclic lactone, MLs or mectin drenches) |
| Abamectin | Paramectin injection
Virbamec injection – cattle, Rycomectin – cattle injection, Genesis injection abamectin, Vetmec – cattle injection,
Abamectin pour-on, Paramectin pour-on, Virbamec pour-on | Injection
Injection
Pour-on
| | | |
|
| Doramectin | Dectomax injectable
Dectomax pour-on | Injection
Pour-on | | | |
| Eprinomectin | Ivomec eprinex pour-on | Pour-on | 0 | 0 | Nil |
| Ivermectin | Ivomec injection, Virbamec LA injection, Noromection injection – cattle and pigs, Bomectin (injection),
Genesis pour-on, Dairymec pour-on, Virbamec LV pour-on, Imax CD, Paramax pour-on, Ivermectin Baymec pour-on, Phonectin pour-on, Ivomec pour-on, Noromectin pour-on, Vetimec pour-on, Ausmectin pour-on, Bovimectin | Injection
Pour-on
| | | |
|
| Moxidectin | Cydectin injection for cattle,
Cydectin Pour-on | Injection
Pour-on | | | |
The above table is to be used as a guide only. Always read and follow the label directions. For detailed information on the registered products contact the chemical manufacturer, your local veterinarian or DPI animal health staff.
Treatments for liver fluke and combined liver fluke and roundworm treatments: please see AG0072 - Control of Liver Fluke.
Footnotes to Table 1
| 1. | The withholding period (WHP) is the minimum period which must elapse between the last administration or application of an agricultural or veterinary chemical product, including treated feed, and the slaughter, collection or harvesting for human consumption or use of the animal commodity. The withholding period is a statutory requirement and on the label of every registered product.
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| 2. | The export slaughter interval (ESI) is the minimum suggested time interval that should elapse between the last application of a drug or veterinary chemical to an animal, and their slaughter for export.
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| 3. | Do not use in lactating cows where milk or milk products may be used for human consumption. Some products can not be used within a period before calving where milk or milk products may be used for human consumption. Please check the label. |
Information sources: Infopest CD Nov 2006 (© Qld DPIF), APVMA (external link) 14 Feb 2007.
The previous version of this Information Note was published in February 2002.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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