Type ii ostertagiosis

With a lot of information available on the control of worms in young cattle one situation which can be overlooked is type II Ostertagiosis. Ostertagia, one of the major worms affecting cattle, has a slightly more complex life cycle than many of the other worms that such as Cooperia. In the case of Ostertagia, infective larvae on the pasture are eaten and then invade the glands which line the abomasums (the cows 4th stomach). There they complete the rest of their life cycle and return to the surface of the abomasum. This can take as little as 18 days with eggs from these worms able to be found as soon as 21 days after initial ingestion from the pasture. This is the basic lifecycle of the majority of intestinal worms. However under certain conditions the larvae can remain in the glands within the tissue of the abomasum for quite long periods – up to 4 months. Importantly these inhibited larvae, which tend to develop over the winter, produce no eggs since they are not yet mature, and will not cause disease until they emerge from the abomasums wall. This situation is what is referred to as Type II Ostertagiosis. Quite what the trigger for emergence is a matter of some debate but in our climate the worms tend to overwinter in the host and emerge in the spring. Removal of adult populations, such as with a conventional or combination oral drench, may signal more larvae to appear, or it may be related to feeding levels. Whatever triggers the worms to emerge, the fact is that these emerging larvae, especially if in great numbers, can cause severe damage to the stomach lining. This can cause sudden severe illness and even death. Early in the disease process there will be no eggs present in the dung, making diagnosis by faecal egg counts difficult, but the presence of worms may be detected on a blood test. Affected stock will range in appearance from normal, scouring and not eating or even very sick and down. Other conditions, such as trace element deficiency and bacterial enteritis may also be involved. The most commonly affected animals are 12 month old animals coming out of winter, but the disease can be seen in 2 year-old animals also coming out of winter. The prevention of Type II Ostertagiosis is relient on having a good preventative drenching programme in place for young animals. Of particular importance with respect to Type II Ostertagiosis is that the ML type drenches (such as Ivermectin, Eprinomectin, Doramectin, Abamectin) are effective at killing the inhibited larvae, whereas Levamisole and Benzamidazoles (Oxfendazole, Albendazole) will not. This is an important point, as due to a lot of documented resistance in Cooperia to the ML type drenches the use of a combination product containing Levamisole and Benzimidazole (which controls Cooperia well) is recommended through late summer and autumn when calves are at the most risk of infection from Cooperia. The use of these Levamisole/Benzimidazole products going into and coming out of winter may lead to poor control of Ostertagia and the potential of being affected by Type II Ostertagiosis. From what we know about Type II Ostertagiosis, the use of an effective drench in the winter/early spring period is very important to prevent this disease occurring. Failure to address any potential infection will have long term consequences as animals with badly damaged stomachs will not make the best use of available dry matter and may take longer to get to target weights and finish than unaffected stock. Contact any of the clinics to discuss and develop a preventative drench plan that is tailored for your individual situation.

Source: http://www.vetfocus.co.nz/webfiles/VetCentreNZ/webpages/images/49993/TypeIIOstertagiosisnewsletter.pdf