Stomach worms: a chronic scourge? Gastrointestinal worms (nematodes) rank among the most common causes of scour, ill-health and lack of thrive in cattle and sheep. Although less deadly than other parasites, such as fluke, stomach worms can become a chronic problem in flocks and herds, resulting in sickly animals and revenue loss for farmers. This means that effective treatment should be an essential part of all good farming plans.  As we have previously often outlined on this pl...