To date some cases of drench resistance in cattle roundworms have been identified in Australia. In younger cattle, the more advanced ML drenches are often better. For adult cattle, in many cases the cheapest ML group drench will do the job. There is no single answer as to which drench to use. Where stocking rates for cattle are high or ostertagiasis is a problem, the use of “mectins” is generally recommended. Some of the benzimidazoles drenches have lesser and a more variable effect on the immature and inhibited stages of Ostertagia than previously thought. The mectins are the most effective against L4 larvae, the benzimidazole drenches follow the mectins and the levamisole group is the least effective. They differ in their activity against the developing and inhibited L4 stages of larvae. Levamisole drenches are used less commonly these days.Īll are effective against adult worms in the abomasum. Benzimidazole or “white” drenches are still sometimes used. The main drenches used are the “mectins” ( or ML drenches). Frequent drenching may be needed just to keep these cattle alive. Severe scouring, loss of weight and even death may result. This coincides with the stress of calving and the emergence of thousands of inhibited L4 larvae from the lining of the fourth stomach. Type-2 disease occurs especially in beef cows calving for the first and second time in the autumn and winter. Beef cattle are affected at 15-20 months. Dairy calves typically suffer type-1 disease at 5-6 months. This disease follows rapid infection with large numbers of 元 larvae from heavily contaminated pastures in the autumn and winter after weaning. Type-1disease usually occurs in calves and young cattle that have high burdens of adult worms in winter and spring. The signs of each type result from the same damage to the fourth stomach or abomasum: The DiseaseĪs explained above, there are two types of disease caused by Ostertagia. If the L4 larvae develop directly, that is if they don’t become inhibited, then adult worms appear 3-4 weeks after infection with 元 larvae.
These can cause a serious type-2 disease when they resume growth and emerge into the abomasum during late summer and early autumn. Large numbers of L4 larvae tend to become inhibited in their development if they are ingested during spring and early summer. The lining of the abomasum is significantly damaged when the larvae emerge as immature adult worms. 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 animal eats the larvae and it then burrows into the wall of the fourth stomach, called the abomassum. The third stage move onto pasture and can survive for many months depending upon how hot and/or are the dry conditions.
Worm eggs are passed out in dung and moult into second and third stages (L2 and 元). 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. Ostertagia and other roundworms of cattle have a simple direct life cycle. Cooperia is not killed by all drenches, however. Usually control of Ostertagia will also control other roundworms of lesser importance such as the small intestinal worm (Cooperia sp). The main gut roundworm of cattle is Ostertagia ostertagi, known commonly as the brown stomach worm. Internal parasites or WORMS have been a bigger problem than usual the last few years.
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